Code

Imported Upstream version 5.5.0
[pkg-collectd.git] / src / daemon / plugin.c
diff --git a/src/daemon/plugin.c b/src/daemon/plugin.c
new file mode 100644 (file)
index 0000000..3d36445
--- /dev/null
@@ -0,0 +1,2727 @@
+/**
+ * collectd - src/plugin.c
+ * Copyright (C) 2005-2014  Florian octo Forster
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Authors:
+ *   Florian octo Forster <octo at collectd.org>
+ *   Sebastian Harl <sh at tokkee.org>
+ **/
+
+#include "collectd.h"
+#include "common.h"
+#include "plugin.h"
+#include "configfile.h"
+#include "filter_chain.h"
+#include "utils_avltree.h"
+#include "utils_cache.h"
+#include "utils_complain.h"
+#include "utils_llist.h"
+#include "utils_heap.h"
+#include "utils_time.h"
+#include "utils_random.h"
+
+#include <ltdl.h>
+
+/*
+ * Private structures
+ */
+struct callback_func_s
+{
+       void *cf_callback;
+       user_data_t cf_udata;
+       plugin_ctx_t cf_ctx;
+};
+typedef struct callback_func_s callback_func_t;
+
+#define RF_SIMPLE  0
+#define RF_COMPLEX 1
+#define RF_REMOVE  65535
+struct read_func_s
+{
+       /* `read_func_t' "inherits" from `callback_func_t'.
+        * The `rf_super' member MUST be the first one in this structure! */
+#define rf_callback rf_super.cf_callback
+#define rf_udata rf_super.cf_udata
+#define rf_ctx rf_super.cf_ctx
+       callback_func_t rf_super;
+       char rf_group[DATA_MAX_NAME_LEN];
+       char *rf_name;
+       int rf_type;
+       cdtime_t rf_interval;
+       cdtime_t rf_effective_interval;
+       cdtime_t rf_next_read;
+};
+typedef struct read_func_s read_func_t;
+
+struct write_queue_s;
+typedef struct write_queue_s write_queue_t;
+struct write_queue_s
+{
+       value_list_t *vl;
+       plugin_ctx_t ctx;
+       write_queue_t *next;
+};
+
+/*
+ * Private variables
+ */
+static c_avl_tree_t *plugins_loaded = NULL;
+
+static llist_t *list_init;
+static llist_t *list_write;
+static llist_t *list_flush;
+static llist_t *list_missing;
+static llist_t *list_shutdown;
+static llist_t *list_log;
+static llist_t *list_notification;
+
+static fc_chain_t *pre_cache_chain = NULL;
+static fc_chain_t *post_cache_chain = NULL;
+
+static c_avl_tree_t *data_sets;
+
+static char *plugindir = NULL;
+
+#ifndef DEFAULT_MAX_READ_INTERVAL
+# define DEFAULT_MAX_READ_INTERVAL TIME_T_TO_CDTIME_T (86400)
+#endif
+static c_heap_t       *read_heap = NULL;
+static llist_t        *read_list;
+static int             read_loop = 1;
+static pthread_mutex_t read_lock = PTHREAD_MUTEX_INITIALIZER;
+static pthread_cond_t  read_cond = PTHREAD_COND_INITIALIZER;
+static pthread_t      *read_threads = NULL;
+static int             read_threads_num = 0;
+static cdtime_t        max_read_interval = DEFAULT_MAX_READ_INTERVAL;
+
+static write_queue_t  *write_queue_head;
+static write_queue_t  *write_queue_tail;
+static long            write_queue_length = 0;
+static _Bool           write_loop = 1;
+static pthread_mutex_t write_lock = PTHREAD_MUTEX_INITIALIZER;
+static pthread_cond_t  write_cond = PTHREAD_COND_INITIALIZER;
+static pthread_t      *write_threads = NULL;
+static size_t          write_threads_num = 0;
+
+static pthread_key_t   plugin_ctx_key;
+static _Bool           plugin_ctx_key_initialized = 0;
+
+static long            write_limit_high = 0;
+static long            write_limit_low = 0;
+
+static derive_t        stats_values_dropped = 0;
+static _Bool           record_statistics = 0;
+
+/*
+ * Static functions
+ */
+static int plugin_dispatch_values_internal (value_list_t *vl);
+
+static const char *plugin_get_dir (void)
+{
+       if (plugindir == NULL)
+               return (PLUGINDIR);
+       else
+               return (plugindir);
+}
+
+static void plugin_update_internal_statistics (void) { /* {{{ */
+       derive_t copy_write_queue_length;
+       value_list_t vl = VALUE_LIST_INIT;
+       value_t values[2];
+
+       copy_write_queue_length = write_queue_length;
+
+       /* Initialize `vl' */
+       vl.values = values;
+       vl.values_len = 2;
+       vl.time = 0;
+       sstrncpy (vl.host, hostname_g, sizeof (vl.host));
+       sstrncpy (vl.plugin, "collectd", sizeof (vl.plugin));
+
+       vl.type_instance[0] = 0;
+       vl.values_len = 1;
+
+       /* Write queue */
+       sstrncpy (vl.plugin_instance, "write_queue",
+                       sizeof (vl.plugin_instance));
+
+       /* Write queue : queue length */
+       vl.values[0].gauge = (gauge_t) copy_write_queue_length;
+       sstrncpy (vl.type, "queue_length", sizeof (vl.type));
+       vl.type_instance[0] = 0;
+       plugin_dispatch_values (&vl);
+
+       /* Write queue : Values dropped (queue length > low limit) */
+       vl.values[0].derive = (derive_t) stats_values_dropped;
+       sstrncpy (vl.type, "derive", sizeof (vl.type));
+       sstrncpy (vl.type_instance, "dropped", sizeof (vl.type_instance));
+       plugin_dispatch_values (&vl);
+
+       /* Cache */
+       sstrncpy (vl.plugin_instance, "cache",
+                       sizeof (vl.plugin_instance));
+
+       /* Cache : Nb entry in cache tree */
+       vl.values[0].gauge = (gauge_t) uc_get_size();
+       sstrncpy (vl.type, "cache_size", sizeof (vl.type));
+       vl.type_instance[0] = 0;
+       plugin_dispatch_values (&vl);
+
+       return;
+} /* }}} void plugin_update_internal_statistics */
+
+static void destroy_callback (callback_func_t *cf) /* {{{ */
+{
+       if (cf == NULL)
+               return;
+
+       if ((cf->cf_udata.data != NULL) && (cf->cf_udata.free_func != NULL))
+       {
+               cf->cf_udata.free_func (cf->cf_udata.data);
+               cf->cf_udata.data = NULL;
+               cf->cf_udata.free_func = NULL;
+       }
+       sfree (cf);
+} /* }}} void destroy_callback */
+
+static void destroy_all_callbacks (llist_t **list) /* {{{ */
+{
+       llentry_t *le;
+
+       if (*list == NULL)
+               return;
+
+       le = llist_head (*list);
+       while (le != NULL)
+       {
+               llentry_t *le_next;
+
+               le_next = le->next;
+
+               sfree (le->key);
+               destroy_callback (le->value);
+               le->value = NULL;
+
+               le = le_next;
+       }
+
+       llist_destroy (*list);
+       *list = NULL;
+} /* }}} void destroy_all_callbacks */
+
+static void destroy_read_heap (void) /* {{{ */
+{
+       if (read_heap == NULL)
+               return;
+
+       while (42)
+       {
+               callback_func_t *cf;
+
+               cf = c_heap_get_root (read_heap);
+               if (cf == NULL)
+                       break;
+
+               destroy_callback (cf);
+       }
+
+       c_heap_destroy (read_heap);
+       read_heap = NULL;
+} /* }}} void destroy_read_heap */
+
+static int register_callback (llist_t **list, /* {{{ */
+               const char *name, callback_func_t *cf)
+{
+       llentry_t *le;
+       char *key;
+
+       if (*list == NULL)
+       {
+               *list = llist_create ();
+               if (*list == NULL)
+               {
+                       ERROR ("plugin: register_callback: "
+                                       "llist_create failed.");
+                       destroy_callback (cf);
+                       return (-1);
+               }
+       }
+
+       key = strdup (name);
+       if (key == NULL)
+       {
+               ERROR ("plugin: register_callback: strdup failed.");
+               destroy_callback (cf);
+               return (-1);
+       }
+
+       le = llist_search (*list, name);
+       if (le == NULL)
+       {
+               le = llentry_create (key, cf);
+               if (le == NULL)
+               {
+                       ERROR ("plugin: register_callback: "
+                                       "llentry_create failed.");
+                       free (key);
+                       destroy_callback (cf);
+                       return (-1);
+               }
+
+               llist_append (*list, le);
+       }
+       else
+       {
+               callback_func_t *old_cf;
+
+               old_cf = le->value;
+               le->value = cf;
+
+               WARNING ("plugin: register_callback: "
+                               "a callback named `%s' already exists - "
+                               "overwriting the old entry!", name);
+
+               destroy_callback (old_cf);
+               sfree (key);
+       }
+
+       return (0);
+} /* }}} int register_callback */
+
+static void log_list_callbacks (llist_t **list, /* {{{ */
+                               const char *comment)
+{
+       char *str;
+       int len;
+       llentry_t *le;
+       int i;
+       int n;
+       char **keys;
+
+       n = llist_size(*list);
+       if (n == 0)
+       {
+               INFO("%s [none]", comment);
+               return;
+       }
+
+       keys = calloc(n, sizeof(char*));
+
+       if (keys == NULL)
+       {
+               ERROR("%s: failed to allocate memory for list of callbacks",
+                     comment);
+
+               return;
+       }
+
+       for (le = llist_head (*list), i = 0, len = 0;
+            le != NULL;
+            le = le->next, i++)
+       {
+               keys[i] = le->key;
+               len += strlen(le->key) + 6;
+       }
+       str = malloc(len + 10);
+       if (str == NULL)
+       {
+               ERROR("%s: failed to allocate memory for list of callbacks",
+                     comment);
+       }
+       else
+       {
+               *str = '\0';
+               strjoin(str, len, keys, n, "', '");
+               INFO("%s ['%s']", comment, str);
+               free(str);
+       }
+       free(keys);
+} /* }}} void log_list_callbacks */
+
+static int create_register_callback (llist_t **list, /* {{{ */
+               const char *name, void *callback, user_data_t *ud)
+{
+       callback_func_t *cf;
+
+       cf = (callback_func_t *) malloc (sizeof (*cf));
+       if (cf == NULL)
+       {
+               ERROR ("plugin: create_register_callback: malloc failed.");
+               return (-1);
+       }
+       memset (cf, 0, sizeof (*cf));
+
+       cf->cf_callback = callback;
+       if (ud == NULL)
+       {
+               cf->cf_udata.data = NULL;
+               cf->cf_udata.free_func = NULL;
+       }
+       else
+       {
+               cf->cf_udata = *ud;
+       }
+
+       cf->cf_ctx = plugin_get_ctx ();
+
+       return (register_callback (list, name, cf));
+} /* }}} int create_register_callback */
+
+static int plugin_unregister (llist_t *list, const char *name) /* {{{ */
+{
+       llentry_t *e;
+
+       if (list == NULL)
+               return (-1);
+
+       e = llist_search (list, name);
+       if (e == NULL)
+               return (-1);
+
+       llist_remove (list, e);
+
+       sfree (e->key);
+       destroy_callback (e->value);
+
+       llentry_destroy (e);
+
+       return (0);
+} /* }}} int plugin_unregister */
+
+/*
+ * (Try to) load the shared object `file'. Won't complain if it isn't a shared
+ * object, but it will bitch about a shared object not having a
+ * ``module_register'' symbol..
+ */
+static int plugin_load_file (char *file, uint32_t flags)
+{
+       lt_dlhandle dlh;
+       void (*reg_handle) (void);
+
+       lt_dlinit ();
+       lt_dlerror (); /* clear errors */
+
+#if LIBTOOL_VERSION == 2
+       if (flags & PLUGIN_FLAGS_GLOBAL) {
+               lt_dladvise advise;
+               lt_dladvise_init(&advise);
+               lt_dladvise_global(&advise);
+               dlh = lt_dlopenadvise(file, advise);
+               lt_dladvise_destroy(&advise);
+       } else {
+               dlh = lt_dlopen (file);
+       }
+#else /* if LIBTOOL_VERSION == 1 */
+       if (flags & PLUGIN_FLAGS_GLOBAL)
+               WARNING ("plugin_load_file: The global flag is not supported, "
+                               "libtool 2 is required for this.");
+       dlh = lt_dlopen (file);
+#endif
+
+       if (dlh == NULL)
+       {
+               char errbuf[1024] = "";
+
+               ssnprintf (errbuf, sizeof (errbuf),
+                               "lt_dlopen (\"%s\") failed: %s. "
+                               "The most common cause for this problem is "
+                               "missing dependencies. Use ldd(1) to check "
+                               "the dependencies of the plugin "
+                               "/ shared object.",
+                               file, lt_dlerror ());
+
+               ERROR ("%s", errbuf);
+               /* Make sure this is printed to STDERR in any case, but also
+                * make sure it's printed only once. */
+               if (list_log != NULL)
+                       fprintf (stderr, "ERROR: %s\n", errbuf);
+
+               return (1);
+       }
+
+       if ((reg_handle = (void (*) (void)) lt_dlsym (dlh, "module_register")) == NULL)
+       {
+               WARNING ("Couldn't find symbol \"module_register\" in \"%s\": %s\n",
+                               file, lt_dlerror ());
+               lt_dlclose (dlh);
+               return (-1);
+       }
+
+       (*reg_handle) ();
+
+       return (0);
+}
+
+static void *plugin_read_thread (void __attribute__((unused)) *args)
+{
+       while (read_loop != 0)
+       {
+               read_func_t *rf;
+               plugin_ctx_t old_ctx;
+               cdtime_t now;
+               int status;
+               int rf_type;
+               int rc;
+
+               /* Get the read function that needs to be read next.
+                * We don't need to hold "read_lock" for the heap, but we need
+                * to call c_heap_get_root() and pthread_cond_wait() in the
+                * same protected block. */
+               pthread_mutex_lock (&read_lock);
+               rf = c_heap_get_root (read_heap);
+               if (rf == NULL)
+               {
+                       pthread_cond_wait (&read_cond, &read_lock);
+                        pthread_mutex_unlock (&read_lock);
+                       continue;
+               }
+               pthread_mutex_unlock (&read_lock);
+
+               if (rf->rf_interval == 0)
+               {
+                       /* this should not happen, because the interval is set
+                        * for each plugin when loading it
+                        * XXX: issue a warning? */
+                       rf->rf_interval = plugin_get_interval ();
+                       rf->rf_effective_interval = rf->rf_interval;
+
+                       rf->rf_next_read = cdtime ();
+               }
+
+               /* sleep until this entry is due,
+                * using pthread_cond_timedwait */
+               pthread_mutex_lock (&read_lock);
+               /* In pthread_cond_timedwait, spurious wakeups are possible
+                * (and really happen, at least on NetBSD with > 1 CPU), thus
+                * we need to re-evaluate the condition every time
+                * pthread_cond_timedwait returns. */
+               rc = 0;
+               while ((read_loop != 0)
+                               && (cdtime () < rf->rf_next_read)
+                               && rc == 0)
+               {
+                       struct timespec ts = { 0 };
+
+                       CDTIME_T_TO_TIMESPEC (rf->rf_next_read, &ts);
+
+                       rc = pthread_cond_timedwait (&read_cond, &read_lock,
+                               &ts);
+               }
+
+               /* Must hold `read_lock' when accessing `rf->rf_type'. */
+               rf_type = rf->rf_type;
+               pthread_mutex_unlock (&read_lock);
+
+               /* Check if we're supposed to stop.. This may have interrupted
+                * the sleep, too. */
+               if (read_loop == 0)
+               {
+                       /* Insert `rf' again, so it can be free'd correctly */
+                       c_heap_insert (read_heap, rf);
+                       break;
+               }
+
+               /* The entry has been marked for deletion. The linked list
+                * entry has already been removed by `plugin_unregister_read'.
+                * All we have to do here is free the `read_func_t' and
+                * continue. */
+               if (rf_type == RF_REMOVE)
+               {
+                       DEBUG ("plugin_read_thread: Destroying the `%s' "
+                                       "callback.", rf->rf_name);
+                       sfree (rf->rf_name);
+                       destroy_callback ((callback_func_t *) rf);
+                       rf = NULL;
+                       continue;
+               }
+
+               DEBUG ("plugin_read_thread: Handling `%s'.", rf->rf_name);
+
+               old_ctx = plugin_set_ctx (rf->rf_ctx);
+
+               if (rf_type == RF_SIMPLE)
+               {
+                       int (*callback) (void);
+
+                       callback = rf->rf_callback;
+                       status = (*callback) ();
+               }
+               else
+               {
+                       plugin_read_cb callback;
+
+                       assert (rf_type == RF_COMPLEX);
+
+                       callback = rf->rf_callback;
+                       status = (*callback) (&rf->rf_udata);
+               }
+
+               plugin_set_ctx (old_ctx);
+
+               /* If the function signals failure, we will increase the
+                * intervals in which it will be called. */
+               if (status != 0)
+               {
+                       rf->rf_effective_interval *= 2;
+                       if (rf->rf_effective_interval > max_read_interval)
+                               rf->rf_effective_interval = max_read_interval;
+
+                       NOTICE ("read-function of plugin `%s' failed. "
+                                       "Will suspend it for %.3f seconds.",
+                                       rf->rf_name,
+                                       CDTIME_T_TO_DOUBLE (rf->rf_effective_interval));
+               }
+               else
+               {
+                       /* Success: Restore the interval, if it was changed. */
+                       rf->rf_effective_interval = rf->rf_interval;
+               }
+
+               /* update the ``next read due'' field */
+               now = cdtime ();
+
+               DEBUG ("plugin_read_thread: Effective interval of the "
+                               "%s plugin is %.3f seconds.",
+                               rf->rf_name,
+                               CDTIME_T_TO_DOUBLE (rf->rf_effective_interval));
+
+               /* Calculate the next (absolute) time at which this function
+                * should be called. */
+               rf->rf_next_read += rf->rf_effective_interval;
+
+               /* Check, if `rf_next_read' is in the past. */
+               if (rf->rf_next_read < now)
+               {
+                       /* `rf_next_read' is in the past. Insert `now'
+                        * so this value doesn't trail off into the
+                        * past too much. */
+                       rf->rf_next_read = now;
+               }
+
+               DEBUG ("plugin_read_thread: Next read of the %s plugin at %.3f.",
+                               rf->rf_name,
+                               CDTIME_T_TO_DOUBLE (rf->rf_next_read));
+
+               /* Re-insert this read function into the heap again. */
+               c_heap_insert (read_heap, rf);
+       } /* while (read_loop) */
+
+       pthread_exit (NULL);
+       return ((void *) 0);
+} /* void *plugin_read_thread */
+
+static void start_read_threads (int num)
+{
+       int i;
+
+       if (read_threads != NULL)
+               return;
+
+       read_threads = (pthread_t *) calloc (num, sizeof (pthread_t));
+       if (read_threads == NULL)
+       {
+               ERROR ("plugin: start_read_threads: calloc failed.");
+               return;
+       }
+
+       read_threads_num = 0;
+       for (i = 0; i < num; i++)
+       {
+               if (pthread_create (read_threads + read_threads_num, NULL,
+                                       plugin_read_thread, NULL) == 0)
+               {
+                       read_threads_num++;
+               }
+               else
+               {
+                       ERROR ("plugin: start_read_threads: pthread_create failed.");
+                       return;
+               }
+       } /* for (i) */
+} /* void start_read_threads */
+
+static void stop_read_threads (void)
+{
+       int i;
+
+       if (read_threads == NULL)
+               return;
+
+       INFO ("collectd: Stopping %i read threads.", read_threads_num);
+
+       pthread_mutex_lock (&read_lock);
+       read_loop = 0;
+       DEBUG ("plugin: stop_read_threads: Signalling `read_cond'");
+       pthread_cond_broadcast (&read_cond);
+       pthread_mutex_unlock (&read_lock);
+
+       for (i = 0; i < read_threads_num; i++)
+       {
+               if (pthread_join (read_threads[i], NULL) != 0)
+               {
+                       ERROR ("plugin: stop_read_threads: pthread_join failed.");
+               }
+               read_threads[i] = (pthread_t) 0;
+       }
+       sfree (read_threads);
+       read_threads_num = 0;
+} /* void stop_read_threads */
+
+static void plugin_value_list_free (value_list_t *vl) /* {{{ */
+{
+       if (vl == NULL)
+               return;
+
+       meta_data_destroy (vl->meta);
+       sfree (vl->values);
+       sfree (vl);
+} /* }}} void plugin_value_list_free */
+
+static value_list_t *plugin_value_list_clone (value_list_t const *vl_orig) /* {{{ */
+{
+       value_list_t *vl;
+
+       if (vl_orig == NULL)
+               return (NULL);
+
+       vl = malloc (sizeof (*vl));
+       if (vl == NULL)
+               return (NULL);
+       memcpy (vl, vl_orig, sizeof (*vl));
+
+       vl->values = calloc (vl_orig->values_len, sizeof (*vl->values));
+       if (vl->values == NULL)
+       {
+               plugin_value_list_free (vl);
+               return (NULL);
+       }
+       memcpy (vl->values, vl_orig->values,
+                       vl_orig->values_len * sizeof (*vl->values));
+
+       vl->meta = meta_data_clone (vl->meta);
+       if ((vl_orig->meta != NULL) && (vl->meta == NULL))
+       {
+               plugin_value_list_free (vl);
+               return (NULL);
+       }
+
+       if (vl->time == 0)
+               vl->time = cdtime ();
+
+       /* Fill in the interval from the thread context, if it is zero. */
+       if (vl->interval == 0)
+       {
+               plugin_ctx_t ctx = plugin_get_ctx ();
+
+               if (ctx.interval != 0)
+                       vl->interval = ctx.interval;
+               else
+               {
+                       char name[6 * DATA_MAX_NAME_LEN];
+                       FORMAT_VL (name, sizeof (name), vl);
+                       ERROR ("plugin_value_list_clone: Unable to determine "
+                                       "interval from context for "
+                                       "value list \"%s\". "
+                                       "This indicates a broken plugin. "
+                                       "Please report this problem to the "
+                                       "collectd mailing list or at "
+                                       "<http://collectd.org/bugs/>.", name);
+                       vl->interval = cf_get_default_interval ();
+               }
+       }
+
+       return (vl);
+} /* }}} value_list_t *plugin_value_list_clone */
+
+static int plugin_write_enqueue (value_list_t const *vl) /* {{{ */
+{
+       write_queue_t *q;
+
+       q = malloc (sizeof (*q));
+       if (q == NULL)
+               return (ENOMEM);
+       q->next = NULL;
+
+       q->vl = plugin_value_list_clone (vl);
+       if (q->vl == NULL)
+       {
+               sfree (q);
+               return (ENOMEM);
+       }
+
+       /* Store context of caller (read plugin); otherwise, it would not be
+        * available to the write plugins when actually dispatching the
+        * value-list later on. */
+       q->ctx = plugin_get_ctx ();
+
+       pthread_mutex_lock (&write_lock);
+
+       if (write_queue_tail == NULL)
+       {
+               write_queue_head = q;
+               write_queue_tail = q;
+               write_queue_length = 1;
+       }
+       else
+       {
+               write_queue_tail->next = q;
+               write_queue_tail = q;
+               write_queue_length += 1;
+       }
+
+       pthread_cond_signal (&write_cond);
+       pthread_mutex_unlock (&write_lock);
+
+       return (0);
+} /* }}} int plugin_write_enqueue */
+
+static value_list_t *plugin_write_dequeue (void) /* {{{ */
+{
+       write_queue_t *q;
+       value_list_t *vl;
+
+       pthread_mutex_lock (&write_lock);
+
+       while (write_loop && (write_queue_head == NULL))
+               pthread_cond_wait (&write_cond, &write_lock);
+
+       if (write_queue_head == NULL)
+       {
+               pthread_mutex_unlock (&write_lock);
+               return (NULL);
+       }
+
+       q = write_queue_head;
+       write_queue_head = q->next;
+       write_queue_length -= 1;
+       if (write_queue_head == NULL) {
+               write_queue_tail = NULL;
+               assert(0 == write_queue_length);
+               }
+
+       pthread_mutex_unlock (&write_lock);
+
+       (void) plugin_set_ctx (q->ctx);
+
+       vl = q->vl;
+       sfree (q);
+       return (vl);
+} /* }}} value_list_t *plugin_write_dequeue */
+
+static void *plugin_write_thread (void __attribute__((unused)) *args) /* {{{ */
+{
+       while (write_loop)
+       {
+               value_list_t *vl = plugin_write_dequeue ();
+               if (vl == NULL)
+                       continue;
+
+               plugin_dispatch_values_internal (vl);
+
+               plugin_value_list_free (vl);
+       }
+
+       pthread_exit (NULL);
+       return ((void *) 0);
+} /* }}} void *plugin_write_thread */
+
+static void start_write_threads (size_t num) /* {{{ */
+{
+       size_t i;
+
+       if (write_threads != NULL)
+               return;
+
+       write_threads = (pthread_t *) calloc (num, sizeof (pthread_t));
+       if (write_threads == NULL)
+       {
+               ERROR ("plugin: start_write_threads: calloc failed.");
+               return;
+       }
+
+       write_threads_num = 0;
+       for (i = 0; i < num; i++)
+       {
+               int status;
+
+               status = pthread_create (write_threads + write_threads_num,
+                               /* attr = */ NULL,
+                               plugin_write_thread,
+                               /* arg = */ NULL);
+               if (status != 0)
+               {
+                       char errbuf[1024];
+                       ERROR ("plugin: start_write_threads: pthread_create failed "
+                                       "with status %i (%s).", status,
+                                       sstrerror (status, errbuf, sizeof (errbuf)));
+                       return;
+               }
+
+               write_threads_num++;
+       } /* for (i) */
+} /* }}} void start_write_threads */
+
+static void stop_write_threads (void) /* {{{ */
+{
+       write_queue_t *q;
+       int i;
+
+       if (write_threads == NULL)
+               return;
+
+       INFO ("collectd: Stopping %zu write threads.", write_threads_num);
+
+       pthread_mutex_lock (&write_lock);
+       write_loop = 0;
+       DEBUG ("plugin: stop_write_threads: Signalling `write_cond'");
+       pthread_cond_broadcast (&write_cond);
+       pthread_mutex_unlock (&write_lock);
+
+       for (i = 0; i < write_threads_num; i++)
+       {
+               if (pthread_join (write_threads[i], NULL) != 0)
+               {
+                       ERROR ("plugin: stop_write_threads: pthread_join failed.");
+               }
+               write_threads[i] = (pthread_t) 0;
+       }
+       sfree (write_threads);
+       write_threads_num = 0;
+
+       pthread_mutex_lock (&write_lock);
+       i = 0;
+       for (q = write_queue_head; q != NULL; )
+       {
+               write_queue_t *q1 = q;
+               plugin_value_list_free (q->vl);
+               q = q->next;
+               sfree (q1);
+               i++;
+       }
+       write_queue_head = NULL;
+       write_queue_tail = NULL;
+       write_queue_length = 0;
+       pthread_mutex_unlock (&write_lock);
+
+       if (i > 0)
+       {
+               WARNING ("plugin: %i value list%s left after shutting down "
+                               "the write threads.",
+                               i, (i == 1) ? " was" : "s were");
+       }
+} /* }}} void stop_write_threads */
+
+/*
+ * Public functions
+ */
+void plugin_set_dir (const char *dir)
+{
+       if (plugindir != NULL)
+               free (plugindir);
+
+       if (dir == NULL)
+               plugindir = NULL;
+       else if ((plugindir = strdup (dir)) == NULL)
+       {
+               char errbuf[1024];
+               ERROR ("strdup failed: %s",
+                               sstrerror (errno, errbuf, sizeof (errbuf)));
+       }
+}
+
+static _Bool plugin_is_loaded (char const *name)
+{
+       int status;
+
+       if (plugins_loaded == NULL)
+               plugins_loaded = c_avl_create ((void *) strcasecmp);
+       assert (plugins_loaded != NULL);
+
+       status = c_avl_get (plugins_loaded, name, /* ret_value = */ NULL);
+       return (status == 0);
+}
+
+static int plugin_mark_loaded (char const *name)
+{
+       char *name_copy;
+       int status;
+
+       name_copy = strdup (name);
+       if (name_copy == NULL)
+               return (ENOMEM);
+
+       status = c_avl_insert (plugins_loaded,
+                       /* key = */ name_copy, /* value = */ NULL);
+       return (status);
+}
+
+static void plugin_free_loaded ()
+{
+       void *key;
+       void *value;
+
+       if (plugins_loaded == NULL)
+               return;
+
+       while (c_avl_pick (plugins_loaded, &key, &value) == 0)
+       {
+               sfree (key);
+               assert (value == NULL);
+       }
+
+       c_avl_destroy (plugins_loaded);
+       plugins_loaded = NULL;
+}
+
+#define BUFSIZE 512
+int plugin_load (char const *plugin_name, uint32_t flags)
+{
+       DIR  *dh;
+       const char *dir;
+       char  filename[BUFSIZE] = "";
+       char  typename[BUFSIZE];
+       int   ret;
+       struct stat    statbuf;
+       struct dirent *de;
+       int status;
+
+       if (plugin_name == NULL)
+               return (EINVAL);
+
+       /* Check if plugin is already loaded and don't do anything in this
+        * case. */
+       if (plugin_is_loaded (plugin_name))
+               return (0);
+
+       dir = plugin_get_dir ();
+       ret = 1;
+
+       /*
+        * XXX: Magic at work:
+        *
+        * Some of the language bindings, for example the Python and Perl
+        * plugins, need to be able to export symbols to the scripts they run.
+        * For this to happen, the "Globals" flag needs to be set.
+        * Unfortunately, this technical detail is hard to explain to the
+        * average user and she shouldn't have to worry about this, ideally.
+        * So in order to save everyone's sanity use a different default for a
+        * handful of special plugins. --octo
+        */
+       if ((strcasecmp ("perl", plugin_name) == 0)
+                       || (strcasecmp ("python", plugin_name) == 0))
+               flags |= PLUGIN_FLAGS_GLOBAL;
+
+       /* `cpu' should not match `cpufreq'. To solve this we add `.so' to the
+        * type when matching the filename */
+       status = ssnprintf (typename, sizeof (typename), "%s.so", plugin_name);
+       if ((status < 0) || ((size_t) status >= sizeof (typename)))
+       {
+               WARNING ("plugin_load: Filename too long: \"%s.so\"", plugin_name);
+               return (-1);
+       }
+
+       if ((dh = opendir (dir)) == NULL)
+       {
+               char errbuf[1024];
+               ERROR ("plugin_load: opendir (%s) failed: %s", dir,
+                               sstrerror (errno, errbuf, sizeof (errbuf)));
+               return (-1);
+       }
+
+       while ((de = readdir (dh)) != NULL)
+       {
+               if (strcasecmp (de->d_name, typename))
+                       continue;
+
+               status = ssnprintf (filename, sizeof (filename),
+                               "%s/%s", dir, de->d_name);
+               if ((status < 0) || ((size_t) status >= sizeof (filename)))
+               {
+                       WARNING ("plugin_load: Filename too long: \"%s/%s\"",
+                                       dir, de->d_name);
+                       continue;
+               }
+
+               if (lstat (filename, &statbuf) == -1)
+               {
+                       char errbuf[1024];
+                       WARNING ("plugin_load: stat (\"%s\") failed: %s",
+                                       filename,
+                                       sstrerror (errno, errbuf, sizeof (errbuf)));
+                       continue;
+               }
+               else if (!S_ISREG (statbuf.st_mode))
+               {
+                       /* don't follow symlinks */
+                       WARNING ("plugin_load: %s is not a regular file.",
+                                       filename);
+                       continue;
+               }
+
+               status = plugin_load_file (filename, flags);
+               if (status == 0)
+               {
+                       /* success */
+                       plugin_mark_loaded (plugin_name);
+                       ret = 0;
+                       break;
+               }
+               else
+               {
+                       ERROR ("plugin_load: Load plugin \"%s\" failed with "
+                                       "status %i.", plugin_name, status);
+               }
+       }
+
+       closedir (dh);
+
+       if (filename[0] == 0)
+               ERROR ("plugin_load: Could not find plugin \"%s\" in %s",
+                               plugin_name, dir);
+
+       return (ret);
+}
+
+/*
+ * The `register_*' functions follow
+ */
+int plugin_register_config (const char *name,
+               int (*callback) (const char *key, const char *val),
+               const char **keys, int keys_num)
+{
+       cf_register (name, callback, keys, keys_num);
+       return (0);
+} /* int plugin_register_config */
+
+int plugin_register_complex_config (const char *type,
+               int (*callback) (oconfig_item_t *))
+{
+       return (cf_register_complex (type, callback));
+} /* int plugin_register_complex_config */
+
+int plugin_register_init (const char *name,
+               int (*callback) (void))
+{
+       return (create_register_callback (&list_init, name, (void *) callback,
+                               /* user_data = */ NULL));
+} /* plugin_register_init */
+
+static int plugin_compare_read_func (const void *arg0, const void *arg1)
+{
+       const read_func_t *rf0;
+       const read_func_t *rf1;
+
+       rf0 = arg0;
+       rf1 = arg1;
+
+       if (rf0->rf_next_read < rf1->rf_next_read)
+               return (-1);
+       else if (rf0->rf_next_read > rf1->rf_next_read)
+               return (1);
+       else
+               return (0);
+} /* int plugin_compare_read_func */
+
+/* Add a read function to both, the heap and a linked list. The linked list if
+ * used to look-up read functions, especially for the remove function. The heap
+ * is used to determine which plugin to read next. */
+static int plugin_insert_read (read_func_t *rf)
+{
+       int status;
+       llentry_t *le;
+
+       rf->rf_next_read = cdtime ();
+       rf->rf_effective_interval = rf->rf_interval;
+
+       pthread_mutex_lock (&read_lock);
+
+       if (read_list == NULL)
+       {
+               read_list = llist_create ();
+               if (read_list == NULL)
+               {
+                       pthread_mutex_unlock (&read_lock);
+                       ERROR ("plugin_insert_read: read_list failed.");
+                       return (-1);
+               }
+       }
+
+       if (read_heap == NULL)
+       {
+               read_heap = c_heap_create (plugin_compare_read_func);
+               if (read_heap == NULL)
+               {
+                       pthread_mutex_unlock (&read_lock);
+                       ERROR ("plugin_insert_read: c_heap_create failed.");
+                       return (-1);
+               }
+       }
+
+       le = llist_search (read_list, rf->rf_name);
+       if (le != NULL)
+       {
+               pthread_mutex_unlock (&read_lock);
+               WARNING ("The read function \"%s\" is already registered. "
+                               "Check for duplicate \"LoadPlugin\" lines "
+                               "in your configuration!",
+                               rf->rf_name);
+               return (EINVAL);
+       }
+
+       le = llentry_create (rf->rf_name, rf);
+       if (le == NULL)
+       {
+               pthread_mutex_unlock (&read_lock);
+               ERROR ("plugin_insert_read: llentry_create failed.");
+               return (-1);
+       }
+
+       status = c_heap_insert (read_heap, rf);
+       if (status != 0)
+       {
+               pthread_mutex_unlock (&read_lock);
+               ERROR ("plugin_insert_read: c_heap_insert failed.");
+               llentry_destroy (le);
+               return (-1);
+       }
+
+       /* This does not fail. */
+       llist_append (read_list, le);
+
+       /* Wake up all the read threads. */
+       pthread_cond_broadcast (&read_cond);
+       pthread_mutex_unlock (&read_lock);
+       return (0);
+} /* int plugin_insert_read */
+
+int plugin_register_read (const char *name,
+               int (*callback) (void))
+{
+       read_func_t *rf;
+       int status;
+
+       rf = malloc (sizeof (*rf));
+       if (rf == NULL)
+       {
+               ERROR ("plugin_register_read: malloc failed.");
+               return (ENOMEM);
+       }
+
+       memset (rf, 0, sizeof (read_func_t));
+       rf->rf_callback = (void *) callback;
+       rf->rf_udata.data = NULL;
+       rf->rf_udata.free_func = NULL;
+       rf->rf_ctx = plugin_get_ctx ();
+       rf->rf_group[0] = '\0';
+       rf->rf_name = strdup (name);
+       rf->rf_type = RF_SIMPLE;
+       rf->rf_interval = plugin_get_interval ();
+
+       status = plugin_insert_read (rf);
+       if (status != 0)
+               sfree (rf);
+
+       return (status);
+} /* int plugin_register_read */
+
+int plugin_register_complex_read (const char *group, const char *name,
+               plugin_read_cb callback,
+               const struct timespec *interval,
+               user_data_t *user_data)
+{
+       read_func_t *rf;
+       int status;
+
+       rf = malloc (sizeof (*rf));
+       if (rf == NULL)
+       {
+               ERROR ("plugin_register_complex_read: malloc failed.");
+               return (ENOMEM);
+       }
+
+       memset (rf, 0, sizeof (read_func_t));
+       rf->rf_callback = (void *) callback;
+       if (group != NULL)
+               sstrncpy (rf->rf_group, group, sizeof (rf->rf_group));
+       else
+               rf->rf_group[0] = '\0';
+       rf->rf_name = strdup (name);
+       rf->rf_type = RF_COMPLEX;
+       if (interval != NULL)
+               rf->rf_interval = TIMESPEC_TO_CDTIME_T (interval);
+       else
+               rf->rf_interval = plugin_get_interval ();
+
+       /* Set user data */
+       if (user_data == NULL)
+       {
+               rf->rf_udata.data = NULL;
+               rf->rf_udata.free_func = NULL;
+       }
+       else
+       {
+               rf->rf_udata = *user_data;
+       }
+
+       rf->rf_ctx = plugin_get_ctx ();
+
+       status = plugin_insert_read (rf);
+       if (status != 0)
+               sfree (rf);
+
+       return (status);
+} /* int plugin_register_complex_read */
+
+int plugin_register_write (const char *name,
+               plugin_write_cb callback, user_data_t *ud)
+{
+       return (create_register_callback (&list_write, name,
+                               (void *) callback, ud));
+} /* int plugin_register_write */
+
+int plugin_register_flush (const char *name,
+               plugin_flush_cb callback, user_data_t *ud)
+{
+       return (create_register_callback (&list_flush, name,
+                               (void *) callback, ud));
+} /* int plugin_register_flush */
+
+int plugin_register_missing (const char *name,
+               plugin_missing_cb callback, user_data_t *ud)
+{
+       return (create_register_callback (&list_missing, name,
+                               (void *) callback, ud));
+} /* int plugin_register_missing */
+
+int plugin_register_shutdown (const char *name,
+               int (*callback) (void))
+{
+       return (create_register_callback (&list_shutdown, name,
+                               (void *) callback, /* user_data = */ NULL));
+} /* int plugin_register_shutdown */
+
+static void plugin_free_data_sets (void)
+{
+       void *key;
+       void *value;
+
+       if (data_sets == NULL)
+               return;
+
+       while (c_avl_pick (data_sets, &key, &value) == 0)
+       {
+               data_set_t *ds = value;
+               /* key is a pointer to ds->type */
+
+               sfree (ds->ds);
+               sfree (ds);
+       }
+
+       c_avl_destroy (data_sets);
+       data_sets = NULL;
+} /* void plugin_free_data_sets */
+
+int plugin_register_data_set (const data_set_t *ds)
+{
+       data_set_t *ds_copy;
+       int i;
+
+       if ((data_sets != NULL)
+                       && (c_avl_get (data_sets, ds->type, NULL) == 0))
+       {
+               NOTICE ("Replacing DS `%s' with another version.", ds->type);
+               plugin_unregister_data_set (ds->type);
+       }
+       else if (data_sets == NULL)
+       {
+               data_sets = c_avl_create ((int (*) (const void *, const void *)) strcmp);
+               if (data_sets == NULL)
+                       return (-1);
+       }
+
+       ds_copy = (data_set_t *) malloc (sizeof (data_set_t));
+       if (ds_copy == NULL)
+               return (-1);
+       memcpy(ds_copy, ds, sizeof (data_set_t));
+
+       ds_copy->ds = (data_source_t *) malloc (sizeof (data_source_t)
+                       * ds->ds_num);
+       if (ds_copy->ds == NULL)
+       {
+               free (ds_copy);
+               return (-1);
+       }
+
+       for (i = 0; i < ds->ds_num; i++)
+               memcpy (ds_copy->ds + i, ds->ds + i, sizeof (data_source_t));
+
+       return (c_avl_insert (data_sets, (void *) ds_copy->type, (void *) ds_copy));
+} /* int plugin_register_data_set */
+
+int plugin_register_log (const char *name,
+               plugin_log_cb callback, user_data_t *ud)
+{
+       return (create_register_callback (&list_log, name,
+                               (void *) callback, ud));
+} /* int plugin_register_log */
+
+int plugin_register_notification (const char *name,
+               plugin_notification_cb callback, user_data_t *ud)
+{
+       return (create_register_callback (&list_notification, name,
+                               (void *) callback, ud));
+} /* int plugin_register_log */
+
+int plugin_unregister_config (const char *name)
+{
+       cf_unregister (name);
+       return (0);
+} /* int plugin_unregister_config */
+
+int plugin_unregister_complex_config (const char *name)
+{
+       cf_unregister_complex (name);
+       return (0);
+} /* int plugin_unregister_complex_config */
+
+int plugin_unregister_init (const char *name)
+{
+       return (plugin_unregister (list_init, name));
+}
+
+int plugin_unregister_read (const char *name) /* {{{ */
+{
+       llentry_t *le;
+       read_func_t *rf;
+
+       if (name == NULL)
+               return (-ENOENT);
+
+       pthread_mutex_lock (&read_lock);
+
+       if (read_list == NULL)
+       {
+               pthread_mutex_unlock (&read_lock);
+               return (-ENOENT);
+       }
+
+       le = llist_search (read_list, name);
+       if (le == NULL)
+       {
+               pthread_mutex_unlock (&read_lock);
+               WARNING ("plugin_unregister_read: No such read function: %s",
+                               name);
+               return (-ENOENT);
+       }
+
+       llist_remove (read_list, le);
+
+       rf = le->value;
+       assert (rf != NULL);
+       rf->rf_type = RF_REMOVE;
+
+       pthread_mutex_unlock (&read_lock);
+
+       llentry_destroy (le);
+
+       DEBUG ("plugin_unregister_read: Marked `%s' for removal.", name);
+
+       return (0);
+} /* }}} int plugin_unregister_read */
+
+void plugin_log_available_writers (void)
+{
+       log_list_callbacks (&list_write, "Available write targets:");
+}
+
+static int compare_read_func_group (llentry_t *e, void *ud) /* {{{ */
+{
+       read_func_t *rf    = e->value;
+       char        *group = ud;
+
+       return strcmp (rf->rf_group, (const char *)group);
+} /* }}} int compare_read_func_group */
+
+int plugin_unregister_read_group (const char *group) /* {{{ */
+{
+       llentry_t *le;
+       read_func_t *rf;
+
+       int found = 0;
+
+       if (group == NULL)
+               return (-ENOENT);
+
+       pthread_mutex_lock (&read_lock);
+
+       if (read_list == NULL)
+       {
+               pthread_mutex_unlock (&read_lock);
+               return (-ENOENT);
+       }
+
+       while (42)
+       {
+               le = llist_search_custom (read_list,
+                               compare_read_func_group, (void *)group);
+
+               if (le == NULL)
+                       break;
+
+               ++found;
+
+               llist_remove (read_list, le);
+
+               rf = le->value;
+               assert (rf != NULL);
+               rf->rf_type = RF_REMOVE;
+
+               llentry_destroy (le);
+
+               DEBUG ("plugin_unregister_read_group: "
+                               "Marked `%s' (group `%s') for removal.",
+                               rf->rf_name, group);
+       }
+
+       pthread_mutex_unlock (&read_lock);
+
+       if (found == 0)
+       {
+               WARNING ("plugin_unregister_read_group: No such "
+                               "group of read function: %s", group);
+               return (-ENOENT);
+       }
+
+       return (0);
+} /* }}} int plugin_unregister_read_group */
+
+int plugin_unregister_write (const char *name)
+{
+       return (plugin_unregister (list_write, name));
+}
+
+int plugin_unregister_flush (const char *name)
+{
+       return (plugin_unregister (list_flush, name));
+}
+
+int plugin_unregister_missing (const char *name)
+{
+       return (plugin_unregister (list_missing, name));
+}
+
+int plugin_unregister_shutdown (const char *name)
+{
+       return (plugin_unregister (list_shutdown, name));
+}
+
+int plugin_unregister_data_set (const char *name)
+{
+       data_set_t *ds;
+
+       if (data_sets == NULL)
+               return (-1);
+
+       if (c_avl_remove (data_sets, name, NULL, (void *) &ds) != 0)
+               return (-1);
+
+       sfree (ds->ds);
+       sfree (ds);
+
+       return (0);
+} /* int plugin_unregister_data_set */
+
+int plugin_unregister_log (const char *name)
+{
+       return (plugin_unregister (list_log, name));
+}
+
+int plugin_unregister_notification (const char *name)
+{
+       return (plugin_unregister (list_notification, name));
+}
+
+void plugin_init_all (void)
+{
+       char const *chain_name;
+       long write_threads_num;
+       llentry_t *le;
+       int status;
+
+       /* Init the value cache */
+       uc_init ();
+
+       if (IS_TRUE (global_option_get ("CollectInternalStats")))
+               record_statistics = 1;
+
+       chain_name = global_option_get ("PreCacheChain");
+       pre_cache_chain = fc_chain_get_by_name (chain_name);
+
+       chain_name = global_option_get ("PostCacheChain");
+       post_cache_chain = fc_chain_get_by_name (chain_name);
+
+       write_limit_high = global_option_get_long ("WriteQueueLimitHigh",
+                       /* default = */ 0);
+       if (write_limit_high < 0)
+       {
+               ERROR ("WriteQueueLimitHigh must be positive or zero.");
+               write_limit_high = 0;
+       }
+
+       write_limit_low = global_option_get_long ("WriteQueueLimitLow",
+                       /* default = */ write_limit_high / 2);
+       if (write_limit_low < 0)
+       {
+               ERROR ("WriteQueueLimitLow must be positive or zero.");
+               write_limit_low = write_limit_high / 2;
+       }
+       else if (write_limit_low > write_limit_high)
+       {
+               ERROR ("WriteQueueLimitLow must not be larger than "
+                               "WriteQueueLimitHigh.");
+               write_limit_low = write_limit_high;
+       }
+
+       write_threads_num = global_option_get_long ("WriteThreads",
+                       /* default = */ 5);
+       if (write_threads_num < 1)
+       {
+               ERROR ("WriteThreads must be positive.");
+               write_threads_num = 5;
+       }
+
+       start_write_threads ((size_t) write_threads_num);
+
+       if ((list_init == NULL) && (read_heap == NULL))
+               return;
+
+       /* Calling all init callbacks before checking if read callbacks
+        * are available allows the init callbacks to register the read
+        * callback. */
+       le = llist_head (list_init);
+       while (le != NULL)
+       {
+               callback_func_t *cf;
+               plugin_init_cb callback;
+               plugin_ctx_t old_ctx;
+
+               cf = le->value;
+               old_ctx = plugin_set_ctx (cf->cf_ctx);
+               callback = cf->cf_callback;
+               status = (*callback) ();
+               plugin_set_ctx (old_ctx);
+
+               if (status != 0)
+               {
+                       ERROR ("Initialization of plugin `%s' "
+                                       "failed with status %i. "
+                                       "Plugin will be unloaded.",
+                                       le->key, status);
+                       /* Plugins that register read callbacks from the init
+                        * callback should take care of appropriate error
+                        * handling themselves. */
+                       /* FIXME: Unload _all_ functions */
+                       plugin_unregister_read (le->key);
+               }
+
+               le = le->next;
+       }
+
+       max_read_interval = global_option_get_time ("MaxReadInterval",
+                       DEFAULT_MAX_READ_INTERVAL);
+
+       /* Start read-threads */
+       if (read_heap != NULL)
+       {
+               const char *rt;
+               int num;
+
+               rt = global_option_get ("ReadThreads");
+               num = atoi (rt);
+               if (num != -1)
+                       start_read_threads ((num > 0) ? num : 5);
+       }
+} /* void plugin_init_all */
+
+/* TODO: Rename this function. */
+void plugin_read_all (void)
+{
+       if(record_statistics) {
+               plugin_update_internal_statistics ();
+       }
+       uc_check_timeout ();
+
+       return;
+} /* void plugin_read_all */
+
+/* Read function called when the `-T' command line argument is given. */
+int plugin_read_all_once (void)
+{
+       int status;
+       int return_status = 0;
+
+       if (read_heap == NULL)
+       {
+               NOTICE ("No read-functions are registered.");
+               return (0);
+       }
+
+       while (42)
+       {
+               read_func_t *rf;
+               plugin_ctx_t old_ctx;
+
+               rf = c_heap_get_root (read_heap);
+               if (rf == NULL)
+                       break;
+
+               old_ctx = plugin_set_ctx (rf->rf_ctx);
+
+               if (rf->rf_type == RF_SIMPLE)
+               {
+                       int (*callback) (void);
+
+                       callback = rf->rf_callback;
+                       status = (*callback) ();
+               }
+               else
+               {
+                       plugin_read_cb callback;
+
+                       callback = rf->rf_callback;
+                       status = (*callback) (&rf->rf_udata);
+               }
+
+               plugin_set_ctx (old_ctx);
+
+               if (status != 0)
+               {
+                       NOTICE ("read-function of plugin `%s' failed.",
+                                       rf->rf_name);
+                       return_status = -1;
+               }
+
+               destroy_callback ((void *) rf);
+       }
+
+       return (return_status);
+} /* int plugin_read_all_once */
+
+int plugin_write (const char *plugin, /* {{{ */
+               const data_set_t *ds, const value_list_t *vl)
+{
+  llentry_t *le;
+  int status;
+
+  if (vl == NULL)
+    return (EINVAL);
+
+  if (list_write == NULL)
+    return (ENOENT);
+
+  if (ds == NULL)
+  {
+    ds = plugin_get_ds (vl->type);
+    if (ds == NULL)
+    {
+      ERROR ("plugin_write: Unable to lookup type `%s'.", vl->type);
+      return (ENOENT);
+    }
+  }
+
+  if (plugin == NULL)
+  {
+    int success = 0;
+    int failure = 0;
+
+    le = llist_head (list_write);
+    while (le != NULL)
+    {
+      callback_func_t *cf = le->value;
+      plugin_write_cb callback;
+
+      /* do not switch plugin context; rather keep the context (interval)
+       * information of the calling read plugin */
+
+      DEBUG ("plugin: plugin_write: Writing values via %s.", le->key);
+      callback = cf->cf_callback;
+      status = (*callback) (ds, vl, &cf->cf_udata);
+      if (status != 0)
+        failure++;
+      else
+        success++;
+
+      le = le->next;
+    }
+
+    if ((success == 0) && (failure != 0))
+      status = -1;
+    else
+      status = 0;
+  }
+  else /* plugin != NULL */
+  {
+    callback_func_t *cf;
+    plugin_write_cb callback;
+
+    le = llist_head (list_write);
+    while (le != NULL)
+    {
+      if (strcasecmp (plugin, le->key) == 0)
+        break;
+
+      le = le->next;
+    }
+
+    if (le == NULL)
+      return (ENOENT);
+
+    cf = le->value;
+
+    /* do not switch plugin context; rather keep the context (interval)
+     * information of the calling read plugin */
+
+    DEBUG ("plugin: plugin_write: Writing values via %s.", le->key);
+    callback = cf->cf_callback;
+    status = (*callback) (ds, vl, &cf->cf_udata);
+  }
+
+  return (status);
+} /* }}} int plugin_write */
+
+int plugin_flush (const char *plugin, cdtime_t timeout, const char *identifier)
+{
+  llentry_t *le;
+
+  if (list_flush == NULL)
+    return (0);
+
+  le = llist_head (list_flush);
+  while (le != NULL)
+  {
+    callback_func_t *cf;
+    plugin_flush_cb callback;
+    plugin_ctx_t old_ctx;
+
+    if ((plugin != NULL)
+        && (strcmp (plugin, le->key) != 0))
+    {
+      le = le->next;
+      continue;
+    }
+
+    cf = le->value;
+    old_ctx = plugin_set_ctx (cf->cf_ctx);
+    callback = cf->cf_callback;
+
+    (*callback) (timeout, identifier, &cf->cf_udata);
+
+    plugin_set_ctx (old_ctx);
+
+    le = le->next;
+  }
+  return (0);
+} /* int plugin_flush */
+
+void plugin_shutdown_all (void)
+{
+       llentry_t *le;
+
+       stop_read_threads ();
+
+       destroy_all_callbacks (&list_init);
+
+       pthread_mutex_lock (&read_lock);
+       llist_destroy (read_list);
+       read_list = NULL;
+       pthread_mutex_unlock (&read_lock);
+
+       destroy_read_heap ();
+
+       plugin_flush (/* plugin = */ NULL,
+                       /* timeout = */ 0,
+                       /* identifier = */ NULL);
+
+       le = NULL;
+       if (list_shutdown != NULL)
+               le = llist_head (list_shutdown);
+
+       while (le != NULL)
+       {
+               callback_func_t *cf;
+               plugin_shutdown_cb callback;
+               plugin_ctx_t old_ctx;
+
+               cf = le->value;
+               old_ctx = plugin_set_ctx (cf->cf_ctx);
+               callback = cf->cf_callback;
+
+               /* Advance the pointer before calling the callback allows
+                * shutdown functions to unregister themselves. If done the
+                * other way around the memory `le' points to will be freed
+                * after callback returns. */
+               le = le->next;
+
+               (*callback) ();
+
+               plugin_set_ctx (old_ctx);
+       }
+
+       stop_write_threads ();
+
+       /* Write plugins which use the `user_data' pointer usually need the
+        * same data available to the flush callback. If this is the case, set
+        * the free_function to NULL when registering the flush callback and to
+        * the real free function when registering the write callback. This way
+        * the data isn't freed twice. */
+       destroy_all_callbacks (&list_flush);
+       destroy_all_callbacks (&list_missing);
+       destroy_all_callbacks (&list_write);
+
+       destroy_all_callbacks (&list_notification);
+       destroy_all_callbacks (&list_shutdown);
+       destroy_all_callbacks (&list_log);
+
+       plugin_free_loaded ();
+       plugin_free_data_sets ();
+} /* void plugin_shutdown_all */
+
+int plugin_dispatch_missing (const value_list_t *vl) /* {{{ */
+{
+  llentry_t *le;
+
+  if (list_missing == NULL)
+    return (0);
+
+  le = llist_head (list_missing);
+  while (le != NULL)
+  {
+    callback_func_t *cf;
+    plugin_missing_cb callback;
+    plugin_ctx_t old_ctx;
+    int status;
+
+    cf = le->value;
+    old_ctx = plugin_set_ctx (cf->cf_ctx);
+    callback = cf->cf_callback;
+
+    status = (*callback) (vl, &cf->cf_udata);
+    plugin_set_ctx (old_ctx);
+    if (status != 0)
+    {
+      if (status < 0)
+      {
+        ERROR ("plugin_dispatch_missing: Callback function \"%s\" "
+            "failed with status %i.",
+            le->key, status);
+        return (status);
+      }
+      else
+      {
+        return (0);
+      }
+    }
+
+    le = le->next;
+  }
+  return (0);
+} /* int }}} plugin_dispatch_missing */
+
+static int plugin_dispatch_values_internal (value_list_t *vl)
+{
+       int status;
+       static c_complain_t no_write_complaint = C_COMPLAIN_INIT_STATIC;
+
+       value_t *saved_values;
+       int      saved_values_len;
+
+       data_set_t *ds;
+
+       int free_meta_data = 0;
+
+       if ((vl == NULL) || (vl->type[0] == 0)
+                       || (vl->values == NULL) || (vl->values_len < 1))
+       {
+               ERROR ("plugin_dispatch_values: Invalid value list "
+                               "from plugin %s.", vl->plugin);
+               return (-1);
+       }
+
+       /* Free meta data only if the calling function didn't specify any. In
+        * this case matches and targets may add some and the calling function
+        * may not expect (and therefore free) that data. */
+       if (vl->meta == NULL)
+               free_meta_data = 1;
+
+       if (list_write == NULL)
+               c_complain_once (LOG_WARNING, &no_write_complaint,
+                               "plugin_dispatch_values: No write callback has been "
+                               "registered. Please load at least one output plugin, "
+                               "if you want the collected data to be stored.");
+
+       if (data_sets == NULL)
+       {
+               ERROR ("plugin_dispatch_values: No data sets registered. "
+                               "Could the types database be read? Check "
+                               "your `TypesDB' setting!");
+               return (-1);
+       }
+
+       if (c_avl_get (data_sets, vl->type, (void *) &ds) != 0)
+       {
+               char ident[6 * DATA_MAX_NAME_LEN];
+
+               FORMAT_VL (ident, sizeof (ident), vl);
+               INFO ("plugin_dispatch_values: Dataset not found: %s "
+                               "(from \"%s\"), check your types.db!",
+                               vl->type, ident);
+               return (-1);
+       }
+
+       /* Assured by plugin_value_list_clone(). The time is determined at
+        * _enqueue_ time. */
+       assert (vl->time != 0);
+       assert (vl->interval != 0);
+
+       DEBUG ("plugin_dispatch_values: time = %.3f; interval = %.3f; "
+                       "host = %s; "
+                       "plugin = %s; plugin_instance = %s; "
+                       "type = %s; type_instance = %s;",
+                       CDTIME_T_TO_DOUBLE (vl->time),
+                       CDTIME_T_TO_DOUBLE (vl->interval),
+                       vl->host,
+                       vl->plugin, vl->plugin_instance,
+                       vl->type, vl->type_instance);
+
+#if COLLECT_DEBUG
+       assert (0 == strcmp (ds->type, vl->type));
+#else
+       if (0 != strcmp (ds->type, vl->type))
+               WARNING ("plugin_dispatch_values: (ds->type = %s) != (vl->type = %s)",
+                               ds->type, vl->type);
+#endif
+
+#if COLLECT_DEBUG
+       assert (ds->ds_num == vl->values_len);
+#else
+       if (ds->ds_num != vl->values_len)
+       {
+               ERROR ("plugin_dispatch_values: ds->type = %s: "
+                               "(ds->ds_num = %i) != "
+                               "(vl->values_len = %i)",
+                               ds->type, ds->ds_num, vl->values_len);
+               return (-1);
+       }
+#endif
+
+       escape_slashes (vl->host, sizeof (vl->host));
+       escape_slashes (vl->plugin, sizeof (vl->plugin));
+       escape_slashes (vl->plugin_instance, sizeof (vl->plugin_instance));
+       escape_slashes (vl->type, sizeof (vl->type));
+       escape_slashes (vl->type_instance, sizeof (vl->type_instance));
+
+       /* Copy the values. This way, we can assure `targets' that they get
+        * dynamically allocated values, which they can free and replace if
+        * they like. */
+       if ((pre_cache_chain != NULL) || (post_cache_chain != NULL))
+       {
+               saved_values     = vl->values;
+               saved_values_len = vl->values_len;
+
+               vl->values = (value_t *) calloc (vl->values_len,
+                               sizeof (*vl->values));
+               if (vl->values == NULL)
+               {
+                       ERROR ("plugin_dispatch_values: calloc failed.");
+                       vl->values = saved_values;
+                       return (-1);
+               }
+               memcpy (vl->values, saved_values,
+                               vl->values_len * sizeof (*vl->values));
+       }
+       else /* if ((pre == NULL) && (post == NULL)) */
+       {
+               saved_values     = NULL;
+               saved_values_len = 0;
+       }
+
+       if (pre_cache_chain != NULL)
+       {
+               status = fc_process_chain (ds, vl, pre_cache_chain);
+               if (status < 0)
+               {
+                       WARNING ("plugin_dispatch_values: Running the "
+                                       "pre-cache chain failed with "
+                                       "status %i (%#x).",
+                                       status, status);
+               }
+               else if (status == FC_TARGET_STOP)
+               {
+                       /* Restore the state of the value_list so that plugins
+                        * don't get confused.. */
+                       if (saved_values != NULL)
+                       {
+                               free (vl->values);
+                               vl->values     = saved_values;
+                               vl->values_len = saved_values_len;
+                       }
+                       return (0);
+               }
+       }
+
+       /* Update the value cache */
+       uc_update (ds, vl);
+
+       if (post_cache_chain != NULL)
+       {
+               status = fc_process_chain (ds, vl, post_cache_chain);
+               if (status < 0)
+               {
+                       WARNING ("plugin_dispatch_values: Running the "
+                                       "post-cache chain failed with "
+                                       "status %i (%#x).",
+                                       status, status);
+               }
+       }
+       else
+               fc_default_action (ds, vl);
+
+       /* Restore the state of the value_list so that plugins don't get
+        * confused.. */
+       if (saved_values != NULL)
+       {
+               free (vl->values);
+               vl->values     = saved_values;
+               vl->values_len = saved_values_len;
+       }
+
+       if ((free_meta_data != 0) && (vl->meta != NULL))
+       {
+               meta_data_destroy (vl->meta);
+               vl->meta = NULL;
+       }
+
+       return (0);
+} /* int plugin_dispatch_values_internal */
+
+static double get_drop_probability (void) /* {{{ */
+{
+       long pos;
+       long size;
+       long wql;
+
+       pthread_mutex_lock (&write_lock);
+       wql = write_queue_length;
+       pthread_mutex_unlock (&write_lock);
+
+       if (wql < write_limit_low)
+               return (0.0);
+       if (wql >= write_limit_high)
+               return (1.0);
+
+       pos = 1 + wql - write_limit_low;
+       size = 1 + write_limit_high - write_limit_low;
+
+       return (((double) pos) / ((double) size));
+} /* }}} double get_drop_probability */
+
+static _Bool check_drop_value (void) /* {{{ */
+{
+       static cdtime_t last_message_time = 0;
+       static pthread_mutex_t last_message_lock = PTHREAD_MUTEX_INITIALIZER;
+
+       double p;
+       double q;
+       int status;
+
+       if (write_limit_high == 0)
+               return (0);
+
+       p = get_drop_probability ();
+       if (p == 0.0)
+               return (0);
+
+       status = pthread_mutex_trylock (&last_message_lock);
+       if (status == 0)
+       {
+               cdtime_t now;
+
+               now = cdtime ();
+               if ((now - last_message_time) > TIME_T_TO_CDTIME_T (1))
+               {
+                       last_message_time = now;
+                       ERROR ("plugin_dispatch_values: Low water mark "
+                                       "reached. Dropping %.0f%% of metrics.",
+                                       100.0 * p);
+               }
+               pthread_mutex_unlock (&last_message_lock);
+       }
+
+       if (p == 1.0)
+               return (1);
+
+       q = cdrand_d ();
+       if (q > p)
+               return (1);
+       else
+               return (0);
+} /* }}} _Bool check_drop_value */
+
+int plugin_dispatch_values (value_list_t const *vl)
+{
+       int status;
+       static pthread_mutex_t statistics_lock = PTHREAD_MUTEX_INITIALIZER;
+
+       if (check_drop_value ()) {
+               if(record_statistics) {
+                       pthread_mutex_lock(&statistics_lock);
+                       stats_values_dropped++;
+                       pthread_mutex_unlock(&statistics_lock);
+               }
+               return (0);
+       }
+
+       status = plugin_write_enqueue (vl);
+       if (status != 0)
+       {
+               char errbuf[1024];
+               ERROR ("plugin_dispatch_values: plugin_write_enqueue failed "
+                               "with status %i (%s).", status,
+                               sstrerror (status, errbuf, sizeof (errbuf)));
+               return (status);
+       }
+
+       return (0);
+}
+
+__attribute__((sentinel))
+int plugin_dispatch_multivalue (value_list_t const *template, /* {{{ */
+               _Bool store_percentage, int store_type, ...)
+{
+       value_list_t *vl;
+       int failed = 0;
+       gauge_t sum = 0.0;
+       va_list ap;
+
+       assert (template->values_len == 1);
+
+  /* Calculate sum for Gauge to calculate percent if needed */
+       if (DS_TYPE_GAUGE == store_type)        {
+               va_start (ap, store_type);
+               while (42)
+               {
+                       char const *name;
+                       gauge_t value;
+
+                       name = va_arg (ap, char const *);
+                       if (name == NULL)
+                               break;
+
+                       value = va_arg (ap, gauge_t);
+                       if (!isnan (value))
+                               sum += value;
+               }
+               va_end (ap);
+       }
+
+
+       vl = plugin_value_list_clone (template);
+       /* plugin_value_list_clone makes sure vl->time is set to non-zero. */
+       if (store_percentage)
+               sstrncpy (vl->type, "percent", sizeof (vl->type));
+
+       va_start (ap, store_type);
+       while (42)
+       {
+               char const *name;
+               int status;
+
+               /* Set the type instance. */
+               name = va_arg (ap, char const *);
+               if (name == NULL)
+                       break;
+               sstrncpy (vl->type_instance, name, sizeof (vl->type_instance));
+
+               /* Set the value. */
+               switch (store_type)
+               {
+               case DS_TYPE_GAUGE:
+                       vl->values[0].gauge = va_arg (ap, gauge_t);
+                       if (store_percentage)
+                               vl->values[0].gauge *= 100.0 / sum;
+                       break;
+               case DS_TYPE_ABSOLUTE:
+                       vl->values[0].absolute = va_arg (ap, absolute_t);
+                       break;
+               case DS_TYPE_COUNTER:
+                       vl->values[0].counter  = va_arg (ap, counter_t);
+                       break;
+               case DS_TYPE_DERIVE:
+                       vl->values[0].derive   = va_arg (ap, derive_t);
+                       break;
+               default:
+                       ERROR ("plugin_dispatch_multivalue: given store_type is incorrect.");
+                       failed++;
+               }
+
+
+               status = plugin_write_enqueue (vl);
+               if (status != 0)
+                       failed++;
+       }
+       va_end (ap);
+
+       plugin_value_list_free (vl);
+       return (failed);
+} /* }}} int plugin_dispatch_multivalue */
+
+int plugin_dispatch_notification (const notification_t *notif)
+{
+       llentry_t *le;
+       /* Possible TODO: Add flap detection here */
+
+       DEBUG ("plugin_dispatch_notification: severity = %i; message = %s; "
+                       "time = %.3f; host = %s;",
+                       notif->severity, notif->message,
+                       CDTIME_T_TO_DOUBLE (notif->time), notif->host);
+
+       /* Nobody cares for notifications */
+       if (list_notification == NULL)
+               return (-1);
+
+       le = llist_head (list_notification);
+       while (le != NULL)
+       {
+               callback_func_t *cf;
+               plugin_notification_cb callback;
+               int status;
+
+               /* do not switch plugin context; rather keep the context
+                * (interval) information of the calling plugin */
+
+               cf = le->value;
+               callback = cf->cf_callback;
+               status = (*callback) (notif, &cf->cf_udata);
+               if (status != 0)
+               {
+                       WARNING ("plugin_dispatch_notification: Notification "
+                                       "callback %s returned %i.",
+                                       le->key, status);
+               }
+
+               le = le->next;
+       }
+
+       return (0);
+} /* int plugin_dispatch_notification */
+
+void plugin_log (int level, const char *format, ...)
+{
+       char msg[1024];
+       va_list ap;
+       llentry_t *le;
+
+#if !COLLECT_DEBUG
+       if (level >= LOG_DEBUG)
+               return;
+#endif
+
+       va_start (ap, format);
+       vsnprintf (msg, sizeof (msg), format, ap);
+       msg[sizeof (msg) - 1] = '\0';
+       va_end (ap);
+
+       if (list_log == NULL)
+       {
+               fprintf (stderr, "%s\n", msg);
+               return;
+       }
+
+       le = llist_head (list_log);
+       while (le != NULL)
+       {
+               callback_func_t *cf;
+               plugin_log_cb callback;
+
+               cf = le->value;
+               callback = cf->cf_callback;
+
+               /* do not switch plugin context; rather keep the context
+                * (interval) information of the calling plugin */
+
+               (*callback) (level, msg, &cf->cf_udata);
+
+               le = le->next;
+       }
+} /* void plugin_log */
+
+int parse_log_severity (const char *severity)
+{
+       int log_level = -1;
+
+       if ((0 == strcasecmp (severity, "emerg"))
+                       || (0 == strcasecmp (severity, "alert"))
+                       || (0 == strcasecmp (severity, "crit"))
+                       || (0 == strcasecmp (severity, "err")))
+               log_level = LOG_ERR;
+       else if (0 == strcasecmp (severity, "warning"))
+               log_level = LOG_WARNING;
+       else if (0 == strcasecmp (severity, "notice"))
+               log_level = LOG_NOTICE;
+       else if (0 == strcasecmp (severity, "info"))
+               log_level = LOG_INFO;
+#if COLLECT_DEBUG
+       else if (0 == strcasecmp (severity, "debug"))
+               log_level = LOG_DEBUG;
+#endif /* COLLECT_DEBUG */
+
+       return (log_level);
+} /* int parse_log_severity */
+
+int parse_notif_severity (const char *severity)
+{
+       int notif_severity = -1;
+
+       if (strcasecmp (severity, "FAILURE") == 0)
+               notif_severity = NOTIF_FAILURE;
+       else if (strcmp (severity, "OKAY") == 0)
+               notif_severity = NOTIF_OKAY;
+       else if ((strcmp (severity, "WARNING") == 0)
+                       || (strcmp (severity, "WARN") == 0))
+               notif_severity = NOTIF_WARNING;
+
+       return (notif_severity);
+} /* int parse_notif_severity */
+
+const data_set_t *plugin_get_ds (const char *name)
+{
+       data_set_t *ds;
+
+       if (data_sets == NULL)
+       {
+               ERROR ("plugin_get_ds: No data sets are defined yet.");
+               return (NULL);
+       }
+
+       if (c_avl_get (data_sets, name, (void *) &ds) != 0)
+       {
+               DEBUG ("No such dataset registered: %s", name);
+               return (NULL);
+       }
+
+       return (ds);
+} /* data_set_t *plugin_get_ds */
+
+static int plugin_notification_meta_add (notification_t *n,
+    const char *name,
+    enum notification_meta_type_e type,
+    const void *value)
+{
+  notification_meta_t *meta;
+  notification_meta_t *tail;
+
+  if ((n == NULL) || (name == NULL) || (value == NULL))
+  {
+    ERROR ("plugin_notification_meta_add: A pointer is NULL!");
+    return (-1);
+  }
+
+  meta = (notification_meta_t *) malloc (sizeof (notification_meta_t));
+  if (meta == NULL)
+  {
+    ERROR ("plugin_notification_meta_add: malloc failed.");
+    return (-1);
+  }
+  memset (meta, 0, sizeof (notification_meta_t));
+
+  sstrncpy (meta->name, name, sizeof (meta->name));
+  meta->type = type;
+
+  switch (type)
+  {
+    case NM_TYPE_STRING:
+    {
+      meta->nm_value.nm_string = strdup ((const char *) value);
+      if (meta->nm_value.nm_string == NULL)
+      {
+        ERROR ("plugin_notification_meta_add: strdup failed.");
+        sfree (meta);
+        return (-1);
+      }
+      break;
+    }
+    case NM_TYPE_SIGNED_INT:
+    {
+      meta->nm_value.nm_signed_int = *((int64_t *) value);
+      break;
+    }
+    case NM_TYPE_UNSIGNED_INT:
+    {
+      meta->nm_value.nm_unsigned_int = *((uint64_t *) value);
+      break;
+    }
+    case NM_TYPE_DOUBLE:
+    {
+      meta->nm_value.nm_double = *((double *) value);
+      break;
+    }
+    case NM_TYPE_BOOLEAN:
+    {
+      meta->nm_value.nm_boolean = *((_Bool *) value);
+      break;
+    }
+    default:
+    {
+      ERROR ("plugin_notification_meta_add: Unknown type: %i", type);
+      sfree (meta);
+      return (-1);
+    }
+  } /* switch (type) */
+
+  meta->next = NULL;
+  tail = n->meta;
+  while ((tail != NULL) && (tail->next != NULL))
+    tail = tail->next;
+
+  if (tail == NULL)
+    n->meta = meta;
+  else
+    tail->next = meta;
+
+  return (0);
+} /* int plugin_notification_meta_add */
+
+int plugin_notification_meta_add_string (notification_t *n,
+    const char *name,
+    const char *value)
+{
+  return (plugin_notification_meta_add (n, name, NM_TYPE_STRING, value));
+}
+
+int plugin_notification_meta_add_signed_int (notification_t *n,
+    const char *name,
+    int64_t value)
+{
+  return (plugin_notification_meta_add (n, name, NM_TYPE_SIGNED_INT, &value));
+}
+
+int plugin_notification_meta_add_unsigned_int (notification_t *n,
+    const char *name,
+    uint64_t value)
+{
+  return (plugin_notification_meta_add (n, name, NM_TYPE_UNSIGNED_INT, &value));
+}
+
+int plugin_notification_meta_add_double (notification_t *n,
+    const char *name,
+    double value)
+{
+  return (plugin_notification_meta_add (n, name, NM_TYPE_DOUBLE, &value));
+}
+
+int plugin_notification_meta_add_boolean (notification_t *n,
+    const char *name,
+    _Bool value)
+{
+  return (plugin_notification_meta_add (n, name, NM_TYPE_BOOLEAN, &value));
+}
+
+int plugin_notification_meta_copy (notification_t *dst,
+    const notification_t *src)
+{
+  notification_meta_t *meta;
+
+  assert (dst != NULL);
+  assert (src != NULL);
+  assert (dst != src);
+  assert ((src->meta == NULL) || (src->meta != dst->meta));
+
+  for (meta = src->meta; meta != NULL; meta = meta->next)
+  {
+    if (meta->type == NM_TYPE_STRING)
+      plugin_notification_meta_add_string (dst, meta->name,
+          meta->nm_value.nm_string);
+    else if (meta->type == NM_TYPE_SIGNED_INT)
+      plugin_notification_meta_add_signed_int (dst, meta->name,
+          meta->nm_value.nm_signed_int);
+    else if (meta->type == NM_TYPE_UNSIGNED_INT)
+      plugin_notification_meta_add_unsigned_int (dst, meta->name,
+          meta->nm_value.nm_unsigned_int);
+    else if (meta->type == NM_TYPE_DOUBLE)
+      plugin_notification_meta_add_double (dst, meta->name,
+          meta->nm_value.nm_double);
+    else if (meta->type == NM_TYPE_BOOLEAN)
+      plugin_notification_meta_add_boolean (dst, meta->name,
+          meta->nm_value.nm_boolean);
+  }
+
+  return (0);
+} /* int plugin_notification_meta_copy */
+
+int plugin_notification_meta_free (notification_meta_t *n)
+{
+  notification_meta_t *this;
+  notification_meta_t *next;
+
+  if (n == NULL)
+  {
+    ERROR ("plugin_notification_meta_free: n == NULL!");
+    return (-1);
+  }
+
+  this = n;
+  while (this != NULL)
+  {
+    next = this->next;
+
+    if (this->type == NM_TYPE_STRING)
+    {
+      free ((char *)this->nm_value.nm_string);
+      this->nm_value.nm_string = NULL;
+    }
+    sfree (this);
+
+    this = next;
+  }
+
+  return (0);
+} /* int plugin_notification_meta_free */
+
+static void plugin_ctx_destructor (void *ctx)
+{
+       sfree (ctx);
+} /* void plugin_ctx_destructor */
+
+static plugin_ctx_t ctx_init = { /* interval = */ 0 };
+
+static plugin_ctx_t *plugin_ctx_create (void)
+{
+       plugin_ctx_t *ctx;
+
+       ctx = malloc (sizeof (*ctx));
+       if (ctx == NULL) {
+               char errbuf[1024];
+               ERROR ("Failed to allocate plugin context: %s",
+                               sstrerror (errno, errbuf, sizeof (errbuf)));
+               return NULL;
+       }
+
+       *ctx = ctx_init;
+       assert (plugin_ctx_key_initialized);
+       pthread_setspecific (plugin_ctx_key, ctx);
+       DEBUG("Created new plugin context.");
+       return (ctx);
+} /* int plugin_ctx_create */
+
+void plugin_init_ctx (void)
+{
+       pthread_key_create (&plugin_ctx_key, plugin_ctx_destructor);
+       plugin_ctx_key_initialized = 1;
+} /* void plugin_init_ctx */
+
+plugin_ctx_t plugin_get_ctx (void)
+{
+       plugin_ctx_t *ctx;
+
+       assert (plugin_ctx_key_initialized);
+       ctx = pthread_getspecific (plugin_ctx_key);
+
+       if (ctx == NULL) {
+               ctx = plugin_ctx_create ();
+               /* this must no happen -- exit() instead? */
+               if (ctx == NULL)
+                       return ctx_init;
+       }
+
+       return (*ctx);
+} /* plugin_ctx_t plugin_get_ctx */
+
+plugin_ctx_t plugin_set_ctx (plugin_ctx_t ctx)
+{
+       plugin_ctx_t *c;
+       plugin_ctx_t old;
+
+       assert (plugin_ctx_key_initialized);
+       c = pthread_getspecific (plugin_ctx_key);
+
+       if (c == NULL) {
+               c = plugin_ctx_create ();
+               /* this must no happen -- exit() instead? */
+               if (c == NULL)
+                       return ctx_init;
+       }
+
+       old = *c;
+       *c = ctx;
+
+       return (old);
+} /* void plugin_set_ctx */
+
+cdtime_t plugin_get_interval (void)
+{
+       cdtime_t interval;
+
+       interval = plugin_get_ctx().interval;
+       if (interval > 0)
+               return interval;
+
+       return cf_get_default_interval ();
+} /* cdtime_t plugin_get_interval */
+
+typedef struct {
+       plugin_ctx_t ctx;
+       void *(*start_routine) (void *);
+       void *arg;
+} plugin_thread_t;
+
+static void *plugin_thread_start (void *arg)
+{
+       plugin_thread_t *plugin_thread = arg;
+
+       void *(*start_routine) (void *) = plugin_thread->start_routine;
+       void *plugin_arg = plugin_thread->arg;
+
+       plugin_set_ctx (plugin_thread->ctx);
+
+       free (plugin_thread);
+
+       return start_routine (plugin_arg);
+} /* void *plugin_thread_start */
+
+int plugin_thread_create (pthread_t *thread, const pthread_attr_t *attr,
+               void *(*start_routine) (void *), void *arg)
+{
+       plugin_thread_t *plugin_thread;
+
+       plugin_thread = malloc (sizeof (*plugin_thread));
+       if (plugin_thread == NULL)
+               return -1;
+
+       plugin_thread->ctx           = plugin_get_ctx ();
+       plugin_thread->start_routine = start_routine;
+       plugin_thread->arg           = arg;
+
+       return pthread_create (thread, attr,
+                       plugin_thread_start, plugin_thread);
+} /* int plugin_thread_create */
+
+/* vim: set sw=8 ts=8 noet fdm=marker : */