import thresholds from thresholds.c

diff --git a/src/write_riemann_threshold.c b/src/write_riemann_threshold.c
new file mode 100644 (file)
index 0000000..8636774
--- /dev/null
+++ b/src/write_riemann_threshold.c
@@ -0,0 +1,1025 @@
+/**
+ * collectd - src/threshold.c
+ * Copyright (C) 2007-2010  Florian Forster
+ * Copyright (C) 2008-2009  Sebastian Harl
+ * Copyright (C) 2009       Andrés J. Díaz
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; only version 2 of the License is applicable.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
+ *
+ * Author:
+ *   Florian octo Forster <octo at collectd.org>
+ *   Sebastian Harl <sh at tokkee.org>
+ *   Andrés J. Díaz <ajdiaz at connectical.com>
+ **/
+
+#include "collectd.h"
+#include "common.h"
+#include "plugin.h"
+#include "utils_avltree.h"
+#include "utils_cache.h"
+
+#include <assert.h>
+#include <pthread.h>
+
+/*
+ * Private data structures
+ * {{{ */
+#define UT_FLAG_INVERT  0x01
+#define UT_FLAG_PERSIST 0x02
+#define UT_FLAG_PERCENTAGE 0x04
+#define UT_FLAG_INTERESTING 0x08
+#define UT_FLAG_PERSIST_OK 0x10
+typedef struct threshold_s
+{
+  char host[DATA_MAX_NAME_LEN];
+  char plugin[DATA_MAX_NAME_LEN];
+  char plugin_instance[DATA_MAX_NAME_LEN];
+  char type[DATA_MAX_NAME_LEN];
+  char type_instance[DATA_MAX_NAME_LEN];
+  char data_source[DATA_MAX_NAME_LEN];
+  gauge_t warning_min;
+  gauge_t warning_max;
+  gauge_t failure_min;
+  gauge_t failure_max;
+  gauge_t hysteresis;
+  unsigned int flags;
+  int hits;
+  struct threshold_s *next;
+} threshold_t;
+/* }}} */
+
+/*
+ * Private (static) variables
+ * {{{ */
+static c_avl_tree_t   *threshold_tree = NULL;
+static pthread_mutex_t threshold_lock = PTHREAD_MUTEX_INITIALIZER;
+/* }}} */
+
+/*
+ * Threshold management
+ * ====================
+ * The following functions add, delete, search, etc. configured thresholds to
+ * the underlying AVL trees.
+ */
+/*
+ * threshold_t *threshold_get
+ *
+ * Retrieve one specific threshold configuration. For looking up a threshold
+ * matching a value_list_t, see "threshold_search" below. Returns NULL if the
+ * specified threshold doesn't exist.
+ */
+static threshold_t *threshold_get (const char *hostname,
+    const char *plugin, const char *plugin_instance,
+    const char *type, const char *type_instance)
+{ /* {{{ */
+  char name[6 * DATA_MAX_NAME_LEN];
+  threshold_t *th = NULL;
+
+  format_name (name, sizeof (name),
+      (hostname == NULL) ? "" : hostname,
+      (plugin == NULL) ? "" : plugin, plugin_instance,
+      (type == NULL) ? "" : type, type_instance);
+  name[sizeof (name) - 1] = '\0';
+
+  if (c_avl_get (threshold_tree, name, (void *) &th) == 0)
+    return (th);
+  else
+    return (NULL);
+} /* }}} threshold_t *threshold_get */
+
+/*
+ * int ut_threshold_add
+ *
+ * Adds a threshold configuration to the list of thresholds. The threshold_t
+ * structure is copied and may be destroyed after this call. Returns zero on
+ * success, non-zero otherwise.
+ */
+static int ut_threshold_add (const threshold_t *th)
+{ /* {{{ */
+  char name[6 * DATA_MAX_NAME_LEN];
+  char *name_copy;
+  threshold_t *th_copy;
+  threshold_t *th_ptr;
+  int status = 0;
+
+  if (format_name (name, sizeof (name), th->host,
+       th->plugin, th->plugin_instance,
+       th->type, th->type_instance) != 0)
+  {
+    ERROR ("ut_threshold_add: format_name failed.");
+    return (-1);
+  }
+
+  name_copy = strdup (name);
+  if (name_copy == NULL)
+  {
+    ERROR ("ut_threshold_add: strdup failed.");
+    return (-1);
+  }
+
+  th_copy = (threshold_t *) malloc (sizeof (threshold_t));
+  if (th_copy == NULL)
+  {
+    sfree (name_copy);
+    ERROR ("ut_threshold_add: malloc failed.");
+    return (-1);
+  }
+  memcpy (th_copy, th, sizeof (threshold_t));
+  th_ptr = NULL;
+
+  DEBUG ("ut_threshold_add: Adding entry `%s'", name);
+
+  pthread_mutex_lock (&threshold_lock);
+
+  th_ptr = threshold_get (th->host, th->plugin, th->plugin_instance,
+      th->type, th->type_instance);
+
+  while ((th_ptr != NULL) && (th_ptr->next != NULL))
+    th_ptr = th_ptr->next;
+
+  if (th_ptr == NULL) /* no such threshold yet */
+  {
+    status = c_avl_insert (threshold_tree, name_copy, th_copy);
+  }
+  else /* th_ptr points to the last threshold in the list */
+  {
+    th_ptr->next = th_copy;
+    /* name_copy isn't needed */
+    sfree (name_copy);
+  }
+
+  pthread_mutex_unlock (&threshold_lock);
+
+  if (status != 0)
+  {
+    ERROR ("ut_threshold_add: c_avl_insert (%s) failed.", name);
+    sfree (name_copy);
+    sfree (th_copy);
+  }
+
+  return (status);
+} /* }}} int ut_threshold_add */
+
+/* 
+ * threshold_t *threshold_search
+ *
+ * Searches for a threshold configuration using all the possible variations of
+ * "Host", "Plugin" and "Type" blocks. Returns NULL if no threshold could be
+ * found.
+ * XXX: This is likely the least efficient function in collectd.
+ */
+static threshold_t *threshold_search (const value_list_t *vl)
+{ /* {{{ */
+  threshold_t *th;
+
+  if ((th = threshold_get (vl->host, vl->plugin, vl->plugin_instance,
+         vl->type, vl->type_instance)) != NULL)
+    return (th);
+  else if ((th = threshold_get (vl->host, vl->plugin, vl->plugin_instance,
+         vl->type, NULL)) != NULL)
+    return (th);
+  else if ((th = threshold_get (vl->host, vl->plugin, NULL,
+         vl->type, vl->type_instance)) != NULL)
+    return (th);
+  else if ((th = threshold_get (vl->host, vl->plugin, NULL,
+         vl->type, NULL)) != NULL)
+    return (th);
+  else if ((th = threshold_get (vl->host, "", NULL,
+         vl->type, vl->type_instance)) != NULL)
+    return (th);
+  else if ((th = threshold_get (vl->host, "", NULL,
+         vl->type, NULL)) != NULL)
+    return (th);
+  else if ((th = threshold_get ("", vl->plugin, vl->plugin_instance,
+         vl->type, vl->type_instance)) != NULL)
+    return (th);
+  else if ((th = threshold_get ("", vl->plugin, vl->plugin_instance,
+         vl->type, NULL)) != NULL)
+    return (th);
+  else if ((th = threshold_get ("", vl->plugin, NULL,
+         vl->type, vl->type_instance)) != NULL)
+    return (th);
+  else if ((th = threshold_get ("", vl->plugin, NULL,
+         vl->type, NULL)) != NULL)
+    return (th);
+  else if ((th = threshold_get ("", "", NULL,
+         vl->type, vl->type_instance)) != NULL)
+    return (th);
+  else if ((th = threshold_get ("", "", NULL,
+         vl->type, NULL)) != NULL)
+    return (th);
+
+  return (NULL);
+} /* }}} threshold_t *threshold_search */
+
+/*
+ * Configuration
+ * =============
+ * The following approximately two hundred functions are used to handle the
+ * configuration and fill the threshold list.
+ * {{{ */
+static int ut_config_type_datasource (threshold_t *th, oconfig_item_t *ci)
+{
+  if ((ci->values_num != 1)
+      || (ci->values[0].type != OCONFIG_TYPE_STRING))
+  {
+    WARNING ("threshold values: The `DataSource' option needs exactly one "
+       "string argument.");
+    return (-1);
+  }
+
+  sstrncpy (th->data_source, ci->values[0].value.string,
+      sizeof (th->data_source));
+
+  return (0);
+} /* int ut_config_type_datasource */
+
+static int ut_config_type_instance (threshold_t *th, oconfig_item_t *ci)
+{
+  if ((ci->values_num != 1)
+      || (ci->values[0].type != OCONFIG_TYPE_STRING))
+  {
+    WARNING ("threshold values: The `Instance' option needs exactly one "
+       "string argument.");
+    return (-1);
+  }
+
+  sstrncpy (th->type_instance, ci->values[0].value.string,
+      sizeof (th->type_instance));
+
+  return (0);
+} /* int ut_config_type_instance */
+
+static int ut_config_type_max (threshold_t *th, oconfig_item_t *ci)
+{
+  if ((ci->values_num != 1)
+      || (ci->values[0].type != OCONFIG_TYPE_NUMBER))
+  {
+    WARNING ("threshold values: The `%s' option needs exactly one "
+       "number argument.", ci->key);
+    return (-1);
+  }
+
+  if (strcasecmp (ci->key, "WarningMax") == 0)
+    th->warning_max = ci->values[0].value.number;
+  else
+    th->failure_max = ci->values[0].value.number;
+
+  return (0);
+} /* int ut_config_type_max */
+
+static int ut_config_type_min (threshold_t *th, oconfig_item_t *ci)
+{
+  if ((ci->values_num != 1)
+      || (ci->values[0].type != OCONFIG_TYPE_NUMBER))
+  {
+    WARNING ("threshold values: The `%s' option needs exactly one "
+       "number argument.", ci->key);
+    return (-1);
+  }
+
+  if (strcasecmp (ci->key, "WarningMin") == 0)
+    th->warning_min = ci->values[0].value.number;
+  else
+    th->failure_min = ci->values[0].value.number;
+
+  return (0);
+} /* int ut_config_type_min */
+
+static int ut_config_type_hits (threshold_t *th, oconfig_item_t *ci)
+{
+  if ((ci->values_num != 1)
+      || (ci->values[0].type != OCONFIG_TYPE_NUMBER))
+  {
+    WARNING ("threshold values: The `%s' option needs exactly one "
+      "number argument.", ci->key);
+    return (-1);
+  }
+
+  th->hits = ci->values[0].value.number;
+
+  return (0);
+} /* int ut_config_type_hits */
+
+static int ut_config_type_hysteresis (threshold_t *th, oconfig_item_t *ci)
+{
+  if ((ci->values_num != 1)
+      || (ci->values[0].type != OCONFIG_TYPE_NUMBER))
+  {
+    WARNING ("threshold values: The `%s' option needs exactly one "
+      "number argument.", ci->key);
+    return (-1);
+  }
+
+  th->hysteresis = ci->values[0].value.number;
+
+  return (0);
+} /* int ut_config_type_hysteresis */
+
+static int ut_config_type (const threshold_t *th_orig, oconfig_item_t *ci)
+{
+  int i;
+  threshold_t th;
+  int status = 0;
+
+  if ((ci->values_num != 1)
+      || (ci->values[0].type != OCONFIG_TYPE_STRING))
+  {
+    WARNING ("threshold values: The `Type' block needs exactly one string "
+       "argument.");
+    return (-1);
+  }
+
+  if (ci->children_num < 1)
+  {
+    WARNING ("threshold values: The `Type' block needs at least one option.");
+    return (-1);
+  }
+
+  memcpy (&th, th_orig, sizeof (th));
+  sstrncpy (th.type, ci->values[0].value.string, sizeof (th.type));
+
+  th.warning_min = NAN;
+  th.warning_max = NAN;
+  th.failure_min = NAN;
+  th.failure_max = NAN;
+  th.hits = 0;
+  th.hysteresis = 0;
+  th.flags = UT_FLAG_INTERESTING; /* interesting by default */
+
+  for (i = 0; i < ci->children_num; i++)
+  {
+    oconfig_item_t *option = ci->children + i;
+    status = 0;
+
+    if (strcasecmp ("Instance", option->key) == 0)
+      status = ut_config_type_instance (&th, option);
+    else if (strcasecmp ("DataSource", option->key) == 0)
+      status = ut_config_type_datasource (&th, option);
+    else if ((strcasecmp ("WarningMax", option->key) == 0)
+       || (strcasecmp ("FailureMax", option->key) == 0))
+      status = ut_config_type_max (&th, option);
+    else if ((strcasecmp ("WarningMin", option->key) == 0)
+       || (strcasecmp ("FailureMin", option->key) == 0))
+      status = ut_config_type_min (&th, option);
+    else if (strcasecmp ("Interesting", option->key) == 0)
+      status = cf_util_get_flag (option, &th.flags, UT_FLAG_INTERESTING);
+    else if (strcasecmp ("Invert", option->key) == 0)
+      status = cf_util_get_flag (option, &th.flags, UT_FLAG_INVERT);
+    else if (strcasecmp ("Persist", option->key) == 0)
+      status = cf_util_get_flag (option, &th.flags, UT_FLAG_PERSIST);
+    else if (strcasecmp ("PersistOK", option->key) == 0)
+      status = cf_util_get_flag (option, &th.flags, UT_FLAG_PERSIST_OK);
+    else if (strcasecmp ("Percentage", option->key) == 0)
+      status = cf_util_get_flag (option, &th.flags, UT_FLAG_PERCENTAGE);
+    else if (strcasecmp ("Hits", option->key) == 0)
+      status = ut_config_type_hits (&th, option);
+    else if (strcasecmp ("Hysteresis", option->key) == 0)
+      status = ut_config_type_hysteresis (&th, option);
+    else
+    {
+      WARNING ("threshold values: Option `%s' not allowed inside a `Type' "
+         "block.", option->key);
+      status = -1;
+    }
+
+    if (status != 0)
+      break;
+  }
+
+  if (status == 0)
+  {
+    status = ut_threshold_add (&th);
+  }
+
+  return (status);
+} /* int ut_config_type */
+
+static int ut_config_plugin_instance (threshold_t *th, oconfig_item_t *ci)
+{
+  if ((ci->values_num != 1)
+      || (ci->values[0].type != OCONFIG_TYPE_STRING))
+  {
+    WARNING ("threshold values: The `Instance' option needs exactly one "
+       "string argument.");
+    return (-1);
+  }
+
+  sstrncpy (th->plugin_instance, ci->values[0].value.string,
+      sizeof (th->plugin_instance));
+
+  return (0);
+} /* int ut_config_plugin_instance */
+
+static int ut_config_plugin (const threshold_t *th_orig, oconfig_item_t *ci)
+{
+  int i;
+  threshold_t th;
+  int status = 0;
+
+  if ((ci->values_num != 1)
+      || (ci->values[0].type != OCONFIG_TYPE_STRING))
+  {
+    WARNING ("threshold values: The `Plugin' block needs exactly one string "
+       "argument.");
+    return (-1);
+  }
+
+  if (ci->children_num < 1)
+  {
+    WARNING ("threshold values: The `Plugin' block needs at least one nested "
+       "block.");
+    return (-1);
+  }
+
+  memcpy (&th, th_orig, sizeof (th));
+  sstrncpy (th.plugin, ci->values[0].value.string, sizeof (th.plugin));
+
+  for (i = 0; i < ci->children_num; i++)
+  {
+    oconfig_item_t *option = ci->children + i;
+    status = 0;
+
+    if (strcasecmp ("Type", option->key) == 0)
+      status = ut_config_type (&th, option);
+    else if (strcasecmp ("Instance", option->key) == 0)
+      status = ut_config_plugin_instance (&th, option);
+    else
+    {
+      WARNING ("threshold values: Option `%s' not allowed inside a `Plugin' "
+         "block.", option->key);
+      status = -1;
+    }
+
+    if (status != 0)
+      break;
+  }
+
+  return (status);
+} /* int ut_config_plugin */
+
+static int ut_config_host (const threshold_t *th_orig, oconfig_item_t *ci)
+{
+  int i;
+  threshold_t th;
+  int status = 0;
+
+  if ((ci->values_num != 1)
+      || (ci->values[0].type != OCONFIG_TYPE_STRING))
+  {
+    WARNING ("threshold values: The `Host' block needs exactly one string "
+       "argument.");
+    return (-1);
+  }
+
+  if (ci->children_num < 1)
+  {
+    WARNING ("threshold values: The `Host' block needs at least one nested "
+       "block.");
+    return (-1);
+  }
+
+  memcpy (&th, th_orig, sizeof (th));
+  sstrncpy (th.host, ci->values[0].value.string, sizeof (th.host));
+
+  for (i = 0; i < ci->children_num; i++)
+  {
+    oconfig_item_t *option = ci->children + i;
+    status = 0;
+
+    if (strcasecmp ("Type", option->key) == 0)
+      status = ut_config_type (&th, option);
+    else if (strcasecmp ("Plugin", option->key) == 0)
+      status = ut_config_plugin (&th, option);
+    else
+    {
+      WARNING ("threshold values: Option `%s' not allowed inside a `Host' "
+         "block.", option->key);
+      status = -1;
+    }
+
+    if (status != 0)
+      break;
+  }
+
+  return (status);
+} /* int ut_config_host */
+/*
+ * End of the functions used to configure threshold values.
+ */
+/* }}} */
+
+/*
+ * int ut_report_state
+ *
+ * Checks if the `state' differs from the old state and creates a notification
+ * if appropriate.
+ * Does not fail.
+ */
+static int ut_report_state (const data_set_t *ds,
+    const value_list_t *vl,
+    const threshold_t *th,
+    const gauge_t *values,
+    int ds_index,
+    int state)
+{ /* {{{ */
+  int state_old;
+  notification_t n;
+
+  char *buf;
+  size_t bufsize;
+
+  int status;
+
+  /* Check if hits matched */
+  if ( (th->hits != 0) )
+  {
+    int hits = uc_get_hits(ds,vl);
+    /* STATE_OKAY resets hits unless PERSIST_OK flag is set. Hits resets if
+     * threshold is hit. */
+    if ( ( (state == STATE_OKAY) && ((th->flags & UT_FLAG_PERSIST_OK) == 0) ) || (hits > th->hits) )
+    {
+        DEBUG("ut_report_state: reset uc_get_hits = 0");
+        uc_set_hits(ds,vl,0); /* reset hit counter and notify */
+    } else {
+      DEBUG("ut_report_state: th->hits = %d, uc_get_hits = %d",th->hits,uc_get_hits(ds,vl));
+      (void) uc_inc_hits(ds,vl,1); /* increase hit counter */
+      return (0);
+    }
+  } /* end check hits */
+
+  state_old = uc_get_state (ds, vl);
+
+  /* If the state didn't change, report if `persistent' is specified. If the
+   * state is `okay', then only report if `persist_ok` flag is set. */
+  if (state == state_old)
+  {
+    if ((th->flags & UT_FLAG_PERSIST) == 0)
+      return (0);
+    else if ( (state == STATE_OKAY) && ((th->flags & UT_FLAG_PERSIST_OK) == 0) )
+      return (0);
+  }
+
+  if (state != state_old)
+    uc_set_state (ds, vl, state);
+
+  NOTIFICATION_INIT_VL (&n, vl);
+
+  buf = n.message;
+  bufsize = sizeof (n.message);
+
+  if (state == STATE_OKAY)
+    n.severity = NOTIF_OKAY;
+  else if (state == STATE_WARNING)
+    n.severity = NOTIF_WARNING;
+  else
+    n.severity = NOTIF_FAILURE;
+
+  n.time = vl->time;
+
+  status = ssnprintf (buf, bufsize, "Host %s, plugin %s",
+      vl->host, vl->plugin);
+  buf += status;
+  bufsize -= status;
+
+  if (vl->plugin_instance[0] != '\0')
+  {
+    status = ssnprintf (buf, bufsize, " (instance %s)",
+       vl->plugin_instance);
+    buf += status;
+    bufsize -= status;
+  }
+
+  status = ssnprintf (buf, bufsize, " type %s", vl->type);
+  buf += status;
+  bufsize -= status;
+
+  if (vl->type_instance[0] != '\0')
+  {
+    status = ssnprintf (buf, bufsize, " (instance %s)",
+       vl->type_instance);
+    buf += status;
+    bufsize -= status;
+  }
+
+  plugin_notification_meta_add_string (&n, "DataSource",
+      ds->ds[ds_index].name);
+  plugin_notification_meta_add_double (&n, "CurrentValue", values[ds_index]);
+  plugin_notification_meta_add_double (&n, "WarningMin", th->warning_min);
+  plugin_notification_meta_add_double (&n, "WarningMax", th->warning_max);
+  plugin_notification_meta_add_double (&n, "FailureMin", th->failure_min);
+  plugin_notification_meta_add_double (&n, "FailureMax", th->failure_max);
+
+  /* Send an okay notification */
+  if (state == STATE_OKAY)
+  {
+    if (state_old == STATE_MISSING)
+      status = ssnprintf (buf, bufsize,
+          ": Value is no longer missing.");
+    else
+      status = ssnprintf (buf, bufsize,
+          ": All data sources are within range again.");
+    buf += status;
+    bufsize -= status;
+  }
+  else
+  {
+    double min;
+    double max;
+
+    min = (state == STATE_ERROR) ? th->failure_min : th->warning_min;
+    max = (state == STATE_ERROR) ? th->failure_max : th->warning_max;
+
+    if (th->flags & UT_FLAG_INVERT)
+    {
+      if (!isnan (min) && !isnan (max))
+      {
+        status = ssnprintf (buf, bufsize, ": Data source \"%s\" is currently "
+            "%f. That is within the %s region of %f%s and %f%s.",
+            ds->ds[ds_index].name, values[ds_index],
+            (state == STATE_ERROR) ? "failure" : "warning",
+            min, ((th->flags & UT_FLAG_PERCENTAGE) != 0) ? "%" : "",
+            max, ((th->flags & UT_FLAG_PERCENTAGE) != 0) ? "%" : "");
+      }
+      else
+      {
+       status = ssnprintf (buf, bufsize, ": Data source \"%s\" is currently "
+           "%f. That is %s the %s threshold of %f%s.",
+           ds->ds[ds_index].name, values[ds_index],
+           isnan (min) ? "below" : "above",
+           (state == STATE_ERROR) ? "failure" : "warning",
+           isnan (min) ? max : min,
+           ((th->flags & UT_FLAG_PERCENTAGE) != 0) ? "%" : "");
+      }
+    }
+    else if (th->flags & UT_FLAG_PERCENTAGE)
+    {
+      gauge_t value;
+      gauge_t sum;
+      int i;
+
+      sum = 0.0;
+      for (i = 0; i < vl->values_len; i++)
+      {
+        if (isnan (values[i]))
+          continue;
+
+        sum += values[i];
+      }
+
+      if (sum == 0.0)
+        value = NAN;
+      else
+        value = 100.0 * values[ds_index] / sum;
+
+      status = ssnprintf (buf, bufsize, ": Data source \"%s\" is currently "
+          "%g (%.2f%%). That is %s the %s threshold of %.2f%%.",
+          ds->ds[ds_index].name, values[ds_index], value,
+          (value < min) ? "below" : "above",
+          (state == STATE_ERROR) ? "failure" : "warning",
+          (value < min) ? min : max);
+    }
+    else /* is not inverted */
+    {
+      status = ssnprintf (buf, bufsize, ": Data source \"%s\" is currently "
+         "%f. That is %s the %s threshold of %f.",
+         ds->ds[ds_index].name, values[ds_index],
+         (values[ds_index] < min) ? "below" : "above",
+         (state == STATE_ERROR) ? "failure" : "warning",
+         (values[ds_index] < min) ? min : max);
+    }
+    buf += status;
+    bufsize -= status;
+  }
+
+  plugin_dispatch_notification (&n);
+
+  plugin_notification_meta_free (n.meta);
+  return (0);
+} /* }}} int ut_report_state */
+
+/*
+ * int ut_check_one_data_source
+ *
+ * Checks one data source against the given threshold configuration. If the
+ * `DataSource' option is set in the threshold, and the name does NOT match,
+ * `okay' is returned. If the threshold does match, its failure and warning
+ * min and max values are checked and `failure' or `warning' is returned if
+ * appropriate.
+ * Does not fail.
+ */
+static int ut_check_one_data_source (const data_set_t *ds,
+    const value_list_t __attribute__((unused)) *vl,
+    const threshold_t *th,
+    const gauge_t *values,
+    int ds_index)
+{ /* {{{ */
+  const char *ds_name;
+  int is_warning = 0;
+  int is_failure = 0;
+  int prev_state = STATE_OKAY;
+
+  /* check if this threshold applies to this data source */
+  if (ds != NULL)
+  {
+    ds_name = ds->ds[ds_index].name;
+    if ((th->data_source[0] != 0)
+       && (strcmp (ds_name, th->data_source) != 0))
+      return (STATE_OKAY);
+  }
+
+  if ((th->flags & UT_FLAG_INVERT) != 0)
+  {
+    is_warning--;
+    is_failure--;
+  }
+
+  /* XXX: This is an experimental code, not optimized, not fast, not reliable,
+   * and probably, do not work as you expect. Enjoy! :D */
+  if ( (th->hysteresis > 0) && ((prev_state = uc_get_state(ds,vl)) != STATE_OKAY) )
+  {
+    switch(prev_state)
+    {
+      case STATE_ERROR:
+       if ( (!isnan (th->failure_min) && ((th->failure_min + th->hysteresis) < values[ds_index])) ||
+            (!isnan (th->failure_max) && ((th->failure_max - th->hysteresis) > values[ds_index])) )
+         return (STATE_OKAY);
+       else
+         is_failure++;
+      case STATE_WARNING:
+       if ( (!isnan (th->warning_min) && ((th->warning_min + th->hysteresis) < values[ds_index])) ||
+            (!isnan (th->warning_max) && ((th->warning_max - th->hysteresis) > values[ds_index])) )
+         return (STATE_OKAY);
+       else
+         is_warning++;
+     }
+  }
+  else { /* no hysteresis */
+    if ((!isnan (th->failure_min) && (th->failure_min > values[ds_index]))
+       || (!isnan (th->failure_max) && (th->failure_max < values[ds_index])))
+      is_failure++;
+
+    if ((!isnan (th->warning_min) && (th->warning_min > values[ds_index]))
+       || (!isnan (th->warning_max) && (th->warning_max < values[ds_index])))
+      is_warning++;
+ }
+
+  if (is_failure != 0)
+    return (STATE_ERROR);
+
+  if (is_warning != 0)
+    return (STATE_WARNING);
+
+  return (STATE_OKAY);
+} /* }}} int ut_check_one_data_source */
+
+/*
+ * int ut_check_one_threshold
+ *
+ * Checks all data sources of a value list against the given threshold, using
+ * the ut_check_one_data_source function above. Returns the worst status,
+ * which is `okay' if nothing has failed.
+ * Returns less than zero if the data set doesn't have any data sources.
+ */
+static int ut_check_one_threshold (const data_set_t *ds,
+    const value_list_t *vl,
+    const threshold_t *th,
+    const gauge_t *values,
+    int *ret_ds_index)
+{ /* {{{ */
+  int ret = -1;
+  int ds_index = -1;
+  int i;
+  gauge_t values_copy[ds->ds_num];
+
+  memcpy (values_copy, values, sizeof (values_copy));
+
+  if ((th->flags & UT_FLAG_PERCENTAGE) != 0)
+  {
+    int num = 0;
+    gauge_t sum=0.0;
+
+    if (ds->ds_num == 1)
+    {
+      WARNING ("ut_check_one_threshold: The %s type has only one data "
+          "source, but you have configured to check this as a percentage. "
+          "That doesn't make much sense, because the percentage will always "
+          "be 100%%!", ds->type);
+    }
+
+    /* Prepare `sum' and `num'. */
+    for (i = 0; i < ds->ds_num; i++)
+      if (!isnan (values[i]))
+      {
+        num++;
+       sum += values[i];
+      }
+
+    if ((num == 0) /* All data sources are undefined. */
+        || (sum == 0.0)) /* Sum is zero, cannot calculate percentage. */
+    {
+      for (i = 0; i < ds->ds_num; i++)
+        values_copy[i] = NAN;
+    }
+    else /* We can actually calculate the percentage. */
+    {
+      for (i = 0; i < ds->ds_num; i++)
+        values_copy[i] = 100.0 * values[i] / sum;
+    }
+  } /* if (UT_FLAG_PERCENTAGE) */
+
+  for (i = 0; i < ds->ds_num; i++)
+  {
+    int status;
+
+    status = ut_check_one_data_source (ds, vl, th, values_copy, i);
+    if (ret < status)
+    {
+      ret = status;
+      ds_index = i;
+    }
+  } /* for (ds->ds_num) */
+
+  if (ret_ds_index != NULL)
+    *ret_ds_index = ds_index;
+
+  return (ret);
+} /* }}} int ut_check_one_threshold */
+
+/*
+ * int ut_check_threshold
+ *
+ * Gets a list of matching thresholds and searches for the worst status by one
+ * of the thresholds. Then reports that status using the ut_report_state
+ * function above. 
+ * Returns zero on success and if no threshold has been configured. Returns
+ * less than zero on failure.
+ */
+static int ut_check_threshold (const data_set_t *ds, const value_list_t *vl,
+    __attribute__((unused)) user_data_t *ud)
+{ /* {{{ */
+  threshold_t *th;
+  gauge_t *values;
+  int status;
+
+  int worst_state = -1;
+  threshold_t *worst_th = NULL;
+  int worst_ds_index = -1;
+
+  if (threshold_tree == NULL)
+    return (0);
+
+  /* Is this lock really necessary? So far, thresholds are only inserted at
+   * startup. -octo */
+  pthread_mutex_lock (&threshold_lock);
+  th = threshold_search (vl);
+  pthread_mutex_unlock (&threshold_lock);
+  if (th == NULL)
+    return (0);
+
+  DEBUG ("ut_check_threshold: Found matching threshold(s)");
+
+  values = uc_get_rate (ds, vl);
+  if (values == NULL)
+    return (0);
+
+  while (th != NULL)
+  {
+    int ds_index = -1;
+
+    status = ut_check_one_threshold (ds, vl, th, values, &ds_index);
+    if (status < 0)
+    {
+      ERROR ("ut_check_threshold: ut_check_one_threshold failed.");
+      sfree (values);
+      return (-1);
+    }
+
+    if (worst_state < status)
+    {
+      worst_state = status;
+      worst_th = th;
+      worst_ds_index = ds_index;
+    }
+
+    th = th->next;
+  } /* while (th) */
+
+  status = ut_report_state (ds, vl, worst_th, values,
+      worst_ds_index, worst_state);
+  if (status != 0)
+  {
+    ERROR ("ut_check_threshold: ut_report_state failed.");
+    sfree (values);
+    return (-1);
+  }
+
+  sfree (values);
+
+  return (0);
+} /* }}} int ut_check_threshold */
+
+/*
+ * int ut_missing
+ *
+ * This function is called whenever a value goes "missing".
+ */
+static int ut_missing (const value_list_t *vl,
+    __attribute__((unused)) user_data_t *ud)
+{ /* {{{ */
+  threshold_t *th;
+  cdtime_t missing_time;
+  char identifier[6 * DATA_MAX_NAME_LEN];
+  notification_t n;
+
+  if (threshold_tree == NULL)
+    return (0);
+
+  th = threshold_search (vl);
+  /* dispatch notifications for "interesting" values only */
+  if ((th == NULL) || ((th->flags & UT_FLAG_INTERESTING) == 0))
+    return (0);
+
+  missing_time = cdtime () - vl->time;
+  FORMAT_VL (identifier, sizeof (identifier), vl);
+
+  NOTIFICATION_INIT_VL (&n, vl);
+  ssnprintf (n.message, sizeof (n.message),
+      "%s has not been updated for %.3f seconds.",
+      identifier, CDTIME_T_TO_DOUBLE (missing_time));
+
+  plugin_dispatch_notification (&n);
+
+  return (0);
+} /* }}} int ut_missing */
+
+int write_riemann_threshold_config (oconfig_item_t *ci)
+{ /* {{{ */
+  int i;
+  int status = 0;
+
+  threshold_t th;
+
+  if (threshold_tree == NULL)
+  {
+    threshold_tree = c_avl_create ((void *) strcmp);
+    if (threshold_tree == NULL)
+    {
+      ERROR ("ut_config: c_avl_create failed.");
+      return (-1);
+    }
+  }
+
+  memset (&th, '\0', sizeof (th));
+  th.warning_min = NAN;
+  th.warning_max = NAN;
+  th.failure_min = NAN;
+  th.failure_max = NAN;
+
+  th.hits = 0;
+  th.hysteresis = 0;
+  th.flags = UT_FLAG_INTERESTING; /* interesting by default */
+    
+  for (i = 0; i < ci->children_num; i++)
+  {
+    oconfig_item_t *option = ci->children + i;
+    status = 0;
+
+    if (strcasecmp ("Type", option->key) == 0)
+      status = ut_config_type (&th, option);
+    else if (strcasecmp ("Plugin", option->key) == 0)
+      status = ut_config_plugin (&th, option);
+    else if (strcasecmp ("Host", option->key) == 0)
+      status = ut_config_host (&th, option);
+    else
+    {
+      WARNING ("threshold values: Option `%s' not allowed here.", option->key);
+      status = -1;
+    }
+
+    if (status != 0)
+      break;
+  }
+
+  if (c_avl_size (threshold_tree) > 0) {
+    plugin_register_missing ("threshold", ut_missing,
+        /* user data = */ NULL);
+    plugin_register_write ("threshold", ut_check_threshold,
+        /* user data = */ NULL);
+  }
+
+  return (status);
+} /* }}} int um_config */
+
+/* vim: set sw=2 ts=8 sts=2 tw=78 et fdm=marker : */