From: Florian Forster <octo@collectd.org>
Date: Fri, 19 Jun 2015 13:11:39 +0000 (+0200)
Subject: Merge branch 'collectd-5.4' into collectd-5.5
X-Git-Tag: collectd-5.5.1~97
X-Git-Url: https://git.tokkee.org/?a=commitdiff_plain;h=81a5fd5046c6a39f580a8fc1a3af837fd5f5aa5c;p=collectd.git

Merge branch 'collectd-5.4' into collectd-5.5
---

81a5fd5046c6a39f580a8fc1a3af837fd5f5aa5c
diff --cc src/daemon/utils_cache.c
index 46b6631c,00000000..7b2f9583
mode 100644,000000..100644
--- a/src/daemon/utils_cache.c
+++ b/src/daemon/utils_cache.c
@@@ -1,987 -1,0 +1,996 @@@
 +/**
 + * collectd - src/utils_cache.c
 + * Copyright (C) 2007-2010  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>
 + **/
 +
 +#include "collectd.h"
 +#include "common.h"
 +#include "plugin.h"
 +#include "utils_avltree.h"
 +#include "utils_cache.h"
 +#include "meta_data.h"
 +
 +#include <assert.h>
 +#include <pthread.h>
 +
 +typedef struct cache_entry_s
 +{
 +	char name[6 * DATA_MAX_NAME_LEN];
 +	int        values_num;
 +	gauge_t   *values_gauge;
 +	value_t   *values_raw;
 +	/* Time contained in the package
 +	 * (for calculating rates) */
 +	cdtime_t last_time;
 +	/* Time according to the local clock
 +	 * (for purging old entries) */
 +	cdtime_t last_update;
 +	/* Interval in which the data is collected
 +	 * (for purding old entries) */
 +	cdtime_t interval;
 +	int state;
 +	int hits;
 +
 +	/*
 +	 * +-----+-----+-----+-----+-----+-----+-----+-----+-----+----
 +	 * !  0  !  1  !  2  !  3  !  4  !  5  !  6  !  7  !  8  ! ...
 +	 * +-----+-----+-----+-----+-----+-----+-----+-----+-----+----
 +	 * ! ds0 ! ds1 ! ds2 ! ds0 ! ds1 ! ds2 ! ds0 ! ds1 ! ds2 ! ...
 +	 * +-----+-----+-----+-----+-----+-----+-----+-----+-----+----
 +	 * !      t = 0      !      t = 1      !      t = 2      ! ...
 +	 * +-----------------+-----------------+-----------------+----
 +	 */
 +	gauge_t *history;
 +	size_t   history_index; /* points to the next position to write to. */
 +	size_t   history_length;
 +
 +	meta_data_t *meta;
 +} cache_entry_t;
 +
 +static c_avl_tree_t   *cache_tree = NULL;
 +static pthread_mutex_t cache_lock = PTHREAD_MUTEX_INITIALIZER;
 +
 +static int cache_compare (const cache_entry_t *a, const cache_entry_t *b)
 +{
 +#if COLLECT_DEBUG
 +  assert ((a != NULL) && (b != NULL));
 +#endif
 +  return (strcmp (a->name, b->name));
 +} /* int cache_compare */
 +
 +static cache_entry_t *cache_alloc (int values_num)
 +{
 +  cache_entry_t *ce;
 +
 +  ce = (cache_entry_t *) malloc (sizeof (cache_entry_t));
 +  if (ce == NULL)
 +  {
 +    ERROR ("utils_cache: cache_alloc: malloc failed.");
 +    return (NULL);
 +  }
 +  memset (ce, '\0', sizeof (cache_entry_t));
 +  ce->values_num = values_num;
 +
 +  ce->values_gauge = calloc (values_num, sizeof (*ce->values_gauge));
 +  ce->values_raw   = calloc (values_num, sizeof (*ce->values_raw));
 +  if ((ce->values_gauge == NULL) || (ce->values_raw == NULL))
 +  {
 +    sfree (ce->values_gauge);
 +    sfree (ce->values_raw);
 +    sfree (ce);
 +    ERROR ("utils_cache: cache_alloc: calloc failed.");
 +    return (NULL);
 +  }
 +
 +  ce->history = NULL;
 +  ce->history_length = 0;
 +  ce->meta = NULL;
 +
 +  return (ce);
 +} /* cache_entry_t *cache_alloc */
 +
 +static void cache_free (cache_entry_t *ce)
 +{
 +  if (ce == NULL)
 +    return;
 +
 +  sfree (ce->values_gauge);
 +  sfree (ce->values_raw);
 +  sfree (ce->history);
 +  if (ce->meta != NULL)
 +  {
 +    meta_data_destroy (ce->meta);
 +    ce->meta = NULL;
 +  }
 +  sfree (ce);
 +} /* void cache_free */
 +
 +static void uc_check_range (const data_set_t *ds, cache_entry_t *ce)
 +{
 +  int i;
 +
 +  for (i = 0; i < ds->ds_num; i++)
 +  {
 +    if (isnan (ce->values_gauge[i]))
 +      continue;
 +    else if (ce->values_gauge[i] < ds->ds[i].min)
 +      ce->values_gauge[i] = NAN;
 +    else if (ce->values_gauge[i] > ds->ds[i].max)
 +      ce->values_gauge[i] = NAN;
 +  }
 +} /* void uc_check_range */
 +
 +static int uc_insert (const data_set_t *ds, const value_list_t *vl,
 +    const char *key)
 +{
 +  int i;
 +  char *key_copy;
 +  cache_entry_t *ce;
 +
 +  /* `cache_lock' has been locked by `uc_update' */
 +
 +  key_copy = strdup (key);
 +  if (key_copy == NULL)
 +  {
 +    ERROR ("uc_insert: strdup failed.");
 +    return (-1);
 +  }
 +
 +  ce = cache_alloc (ds->ds_num);
 +  if (ce == NULL)
 +  {
 +    sfree (key_copy);
 +    ERROR ("uc_insert: cache_alloc (%i) failed.", ds->ds_num);
 +    return (-1);
 +  }
 +
 +  sstrncpy (ce->name, key, sizeof (ce->name));
 +
 +  for (i = 0; i < ds->ds_num; i++)
 +  {
 +    switch (ds->ds[i].type)
 +    {
 +      case DS_TYPE_COUNTER:
 +	ce->values_gauge[i] = NAN;
 +	ce->values_raw[i].counter = vl->values[i].counter;
 +	break;
 +
 +      case DS_TYPE_GAUGE:
 +	ce->values_gauge[i] = vl->values[i].gauge;
 +	ce->values_raw[i].gauge = vl->values[i].gauge;
 +	break;
 +
 +      case DS_TYPE_DERIVE:
 +	ce->values_gauge[i] = NAN;
 +	ce->values_raw[i].derive = vl->values[i].derive;
 +	break;
 +
 +      case DS_TYPE_ABSOLUTE:
 +	ce->values_gauge[i] = NAN;
 +	if (vl->interval > 0)
 +	  ce->values_gauge[i] = ((double) vl->values[i].absolute)
 +	    / CDTIME_T_TO_DOUBLE (vl->interval);
 +	ce->values_raw[i].absolute = vl->values[i].absolute;
 +	break;
 +	
 +      default:
 +	/* This shouldn't happen. */
 +	ERROR ("uc_insert: Don't know how to handle data source type %i.",
 +	    ds->ds[i].type);
 +	return (-1);
 +    } /* switch (ds->ds[i].type) */
 +  } /* for (i) */
 +
 +  /* Prune invalid gauge data */
 +  uc_check_range (ds, ce);
 +
 +  ce->last_time = vl->time;
 +  ce->last_update = cdtime ();
 +  ce->interval = vl->interval;
 +  ce->state = STATE_OKAY;
 +
 +  if (c_avl_insert (cache_tree, key_copy, ce) != 0)
 +  {
 +    sfree (key_copy);
 +    ERROR ("uc_insert: c_avl_insert failed.");
 +    return (-1);
 +  }
 +
 +  DEBUG ("uc_insert: Added %s to the cache.", key);
 +  return (0);
 +} /* int uc_insert */
 +
 +int uc_init (void)
 +{
 +  if (cache_tree == NULL)
 +    cache_tree = c_avl_create ((int (*) (const void *, const void *))
 +	cache_compare);
 +
 +  return (0);
 +} /* int uc_init */
 +
 +int uc_check_timeout (void)
 +{
 +  cdtime_t now;
 +  cache_entry_t *ce;
 +
 +  char **keys = NULL;
 +  cdtime_t *keys_time = NULL;
 +  cdtime_t *keys_interval = NULL;
 +  int keys_len = 0;
 +
 +  char *key;
 +  c_avl_iterator_t *iter;
 +
 +  int status;
 +  int i;
 +  
 +  pthread_mutex_lock (&cache_lock);
 +
 +  now = cdtime ();
 +
 +  /* Build a list of entries to be flushed */
 +  iter = c_avl_get_iterator (cache_tree);
 +  while (c_avl_iterator_next (iter, (void *) &key, (void *) &ce) == 0)
 +  {
 +    char **tmp;
 +    cdtime_t *tmp_time;
 +
 +    /* If the entry is fresh enough, continue. */
 +    if ((now - ce->last_update) < (ce->interval * timeout_g))
 +      continue;
 +
 +    /* If entry has not been updated, add to `keys' array */
 +    tmp = (char **) realloc ((void *) keys,
 +	(keys_len + 1) * sizeof (char *));
 +    if (tmp == NULL)
 +    {
 +      ERROR ("uc_check_timeout: realloc failed.");
 +      continue;
 +    }
 +    keys = tmp;
 +
 +    tmp_time = realloc (keys_time, (keys_len + 1) * sizeof (*keys_time));
 +    if (tmp_time == NULL)
 +    {
 +      ERROR ("uc_check_timeout: realloc failed.");
 +      continue;
 +    }
 +    keys_time = tmp_time;
 +
 +    tmp_time = realloc (keys_interval, (keys_len + 1) * sizeof (*keys_interval));
 +    if (tmp_time == NULL)
 +    {
 +      ERROR ("uc_check_timeout: realloc failed.");
 +      continue;
 +    }
 +    keys_interval = tmp_time;
 +
 +    keys[keys_len] = strdup (key);
 +    if (keys[keys_len] == NULL)
 +    {
 +      ERROR ("uc_check_timeout: strdup failed.");
 +      continue;
 +    }
 +    keys_time[keys_len] = ce->last_time;
 +    keys_interval[keys_len] = ce->interval;
 +
 +    keys_len++;
 +  } /* while (c_avl_iterator_next) */
 +
 +  c_avl_iterator_destroy (iter);
 +  pthread_mutex_unlock (&cache_lock);
 +
 +  if (keys_len == 0)
++  {
++    /* realloc() may have been called for these. */
++    sfree (keys);
++    sfree (keys_time);
++    sfree (keys_interval);
 +    return (0);
++  }
 +
 +  /* Call the "missing" callback for each value. Do this before removing the
 +   * value from the cache, so that callbacks can still access the data stored,
 +   * including plugin specific meta data, rates, history, …. This must be done
 +   * without holding the lock, otherwise we will run into a deadlock if a
 +   * plugin calls the cache interface. */
 +  for (i = 0; i < keys_len; i++)
 +  {
 +    value_list_t vl = VALUE_LIST_INIT;
 +
 +    vl.values = NULL;
 +    vl.values_len = 0;
 +    vl.meta = NULL;
 +
 +    status = parse_identifier_vl (keys[i], &vl);
 +    if (status != 0)
 +    {
 +      ERROR ("uc_check_timeout: parse_identifier_vl (\"%s\") failed.", keys[i]);
 +      continue;
 +    }
 +
 +    vl.time = keys_time[i];
 +    vl.interval = keys_interval[i];
 +
 +    plugin_dispatch_missing (&vl);
 +  } /* for (i = 0; i < keys_len; i++) */
 +
 +  /* Now actually remove all the values from the cache. We don't re-evaluate
 +   * the timestamp again, so in theory it is possible we remove a value after
 +   * it is updated here. */
 +  pthread_mutex_lock (&cache_lock);
 +  for (i = 0; i < keys_len; i++)
 +  {
 +    key = NULL;
 +    ce = NULL;
 +
 +    status = c_avl_remove (cache_tree, keys[i],
 +	(void *) &key, (void *) &ce);
 +    if (status != 0)
 +    {
 +      ERROR ("uc_check_timeout: c_avl_remove (\"%s\") failed.", keys[i]);
 +      sfree (keys[i]);
 +      continue;
 +    }
 +
 +    sfree (keys[i]);
 +    sfree (key);
 +    cache_free (ce);
 +  } /* for (i = 0; i < keys_len; i++) */
 +  pthread_mutex_unlock (&cache_lock);
 +
 +  sfree (keys);
 +  sfree (keys_time);
 +  sfree (keys_interval);
 +
 +  return (0);
 +} /* int uc_check_timeout */
 +
 +int uc_update (const data_set_t *ds, const value_list_t *vl)
 +{
 +  char name[6 * DATA_MAX_NAME_LEN];
 +  cache_entry_t *ce = NULL;
 +  int status;
 +  int i;
 +
 +  if (FORMAT_VL (name, sizeof (name), vl) != 0)
 +  {
 +    ERROR ("uc_update: FORMAT_VL failed.");
 +    return (-1);
 +  }
 +
 +  pthread_mutex_lock (&cache_lock);
 +
 +  status = c_avl_get (cache_tree, name, (void *) &ce);
 +  if (status != 0) /* entry does not yet exist */
 +  {
 +    status = uc_insert (ds, vl, name);
 +    pthread_mutex_unlock (&cache_lock);
 +    return (status);
 +  }
 +
 +  assert (ce != NULL);
 +  assert (ce->values_num == ds->ds_num);
 +
 +  if (ce->last_time >= vl->time)
 +  {
 +    pthread_mutex_unlock (&cache_lock);
 +    NOTICE ("uc_update: Value too old: name = %s; value time = %.3f; "
 +	"last cache update = %.3f;",
 +	name,
 +	CDTIME_T_TO_DOUBLE (vl->time),
 +	CDTIME_T_TO_DOUBLE (ce->last_time));
 +    return (-1);
 +  }
 +
 +  for (i = 0; i < ds->ds_num; i++)
 +  {
 +    switch (ds->ds[i].type)
 +    {
 +      case DS_TYPE_COUNTER:
 +	{
 +	  counter_t diff;
 +
 +	  /* check if the counter has wrapped around */
 +	  if (vl->values[i].counter < ce->values_raw[i].counter)
 +	  {
 +	    if (ce->values_raw[i].counter <= 4294967295U)
 +	      diff = (4294967295U - ce->values_raw[i].counter)
 +		+ vl->values[i].counter;
 +	    else
 +	      diff = (18446744073709551615ULL - ce->values_raw[i].counter)
 +		+ vl->values[i].counter;
 +	  }
 +	  else /* counter has NOT wrapped around */
 +	  {
 +	    diff = vl->values[i].counter - ce->values_raw[i].counter;
 +	  }
 +
 +	  ce->values_gauge[i] = ((double) diff)
 +	    / (CDTIME_T_TO_DOUBLE (vl->time - ce->last_time));
 +	  ce->values_raw[i].counter = vl->values[i].counter;
 +	}
 +	break;
 +
 +      case DS_TYPE_GAUGE:
 +	ce->values_raw[i].gauge = vl->values[i].gauge;
 +	ce->values_gauge[i] = vl->values[i].gauge;
 +	break;
 +
 +      case DS_TYPE_DERIVE:
 +	{
 +	  derive_t diff;
 +
 +	  diff = vl->values[i].derive - ce->values_raw[i].derive;
 +
 +	  ce->values_gauge[i] = ((double) diff)
 +	    / (CDTIME_T_TO_DOUBLE (vl->time - ce->last_time));
 +	  ce->values_raw[i].derive = vl->values[i].derive;
 +	}
 +	break;
 +
 +      case DS_TYPE_ABSOLUTE:
 +	ce->values_gauge[i] = ((double) vl->values[i].absolute)
 +	  / (CDTIME_T_TO_DOUBLE (vl->time - ce->last_time));
 +	ce->values_raw[i].absolute = vl->values[i].absolute;
 +	break;
 +
 +      default:
 +	/* This shouldn't happen. */
 +	pthread_mutex_unlock (&cache_lock);
 +	ERROR ("uc_update: Don't know how to handle data source type %i.",
 +	    ds->ds[i].type);
 +	return (-1);
 +    } /* switch (ds->ds[i].type) */
 +
 +    DEBUG ("uc_update: %s: ds[%i] = %lf", name, i, ce->values_gauge[i]);
 +  } /* for (i) */
 +
 +  /* Update the history if it exists. */
 +  if (ce->history != NULL)
 +  {
 +    assert (ce->history_index < ce->history_length);
 +    for (i = 0; i < ce->values_num; i++)
 +    {
 +      size_t hist_idx = (ce->values_num * ce->history_index) + i;
 +      ce->history[hist_idx] = ce->values_gauge[i];
 +    }
 +
 +    assert (ce->history_length > 0);
 +    ce->history_index = (ce->history_index + 1) % ce->history_length;
 +  }
 +
 +  /* Prune invalid gauge data */
 +  uc_check_range (ds, ce);
 +
 +  ce->last_time = vl->time;
 +  ce->last_update = cdtime ();
 +  ce->interval = vl->interval;
 +
 +  pthread_mutex_unlock (&cache_lock);
 +
 +  return (0);
 +} /* int uc_update */
 +
 +int uc_get_rate_by_name (const char *name, gauge_t **ret_values, size_t *ret_values_num)
 +{
 +  gauge_t *ret = NULL;
 +  size_t ret_num = 0;
 +  cache_entry_t *ce = NULL;
 +  int status = 0;
 +
 +  pthread_mutex_lock (&cache_lock);
 +
 +  if (c_avl_get (cache_tree, name, (void *) &ce) == 0)
 +  {
 +    assert (ce != NULL);
 +
 +    /* remove missing values from getval */
 +    if (ce->state == STATE_MISSING)
 +    {
 +      status = -1;
 +    }
 +    else
 +    {
 +      ret_num = ce->values_num;
 +      ret = (gauge_t *) malloc (ret_num * sizeof (gauge_t));
 +      if (ret == NULL)
 +      {
 +        ERROR ("utils_cache: uc_get_rate_by_name: malloc failed.");
 +        status = -1;
 +      }
 +      else
 +      {
 +        memcpy (ret, ce->values_gauge, ret_num * sizeof (gauge_t));
 +      }
 +    }
 +  }
 +  else
 +  {
 +    DEBUG ("utils_cache: uc_get_rate_by_name: No such value: %s", name);
 +    status = -1;
 +  }
 +
 +  pthread_mutex_unlock (&cache_lock);
 +
 +  if (status == 0)
 +  {
 +    *ret_values = ret;
 +    *ret_values_num = ret_num;
 +  }
 +
 +  return (status);
 +} /* gauge_t *uc_get_rate_by_name */
 +
 +gauge_t *uc_get_rate (const data_set_t *ds, const value_list_t *vl)
 +{
 +  char name[6 * DATA_MAX_NAME_LEN];
 +  gauge_t *ret = NULL;
 +  size_t ret_num = 0;
 +  int status;
 +
 +  if (FORMAT_VL (name, sizeof (name), vl) != 0)
 +  {
 +    ERROR ("utils_cache: uc_get_rate: FORMAT_VL failed.");
 +    return (NULL);
 +  }
 +
 +  status = uc_get_rate_by_name (name, &ret, &ret_num);
 +  if (status != 0)
 +    return (NULL);
 +
 +  /* This is important - the caller has no other way of knowing how many
 +   * values are returned. */
 +  if (ret_num != (size_t) ds->ds_num)
 +  {
 +    ERROR ("utils_cache: uc_get_rate: ds[%s] has %i values, "
 +	"but uc_get_rate_by_name returned %zu.",
 +	ds->type, ds->ds_num, ret_num);
 +    sfree (ret);
 +    return (NULL);
 +  }
 +
 +  return (ret);
 +} /* gauge_t *uc_get_rate */
 +
 +size_t uc_get_size() {
 +  size_t size_arrays = 0;
 +
 +  pthread_mutex_lock (&cache_lock);
 +  size_arrays = (size_t) c_avl_size (cache_tree);
 +  pthread_mutex_unlock (&cache_lock);
 +
 +  return (size_arrays);
 +}
 +
 +int uc_get_names (char ***ret_names, cdtime_t **ret_times, size_t *ret_number)
 +{
 +  c_avl_iterator_t *iter;
 +  char *key;
 +  cache_entry_t *value;
 +
 +  char **names = NULL;
 +  cdtime_t *times = NULL;
 +  size_t number = 0;
 +  size_t size_arrays = 0;
 +
 +  int status = 0;
 +
 +  if ((ret_names == NULL) || (ret_number == NULL))
 +    return (-1);
 +
 +  pthread_mutex_lock (&cache_lock);
 +
 +  size_arrays = (size_t) c_avl_size (cache_tree);
 +  if (size_arrays < 1)
 +  {
 +    /* Handle the "no values" case here, to avoid the error message when
 +     * calloc() returns NULL. */
 +    pthread_mutex_unlock (&cache_lock);
 +    return (0);
 +  }
 +
 +  names = calloc (size_arrays, sizeof (*names));
 +  times = calloc (size_arrays, sizeof (*times));
 +  if ((names == NULL) || (times == NULL))
 +  {
 +    ERROR ("uc_get_names: calloc failed.");
 +    sfree (names);
 +    sfree (times);
 +    pthread_mutex_unlock (&cache_lock);
 +    return (ENOMEM);
 +  }
 +
 +  iter = c_avl_get_iterator (cache_tree);
 +  while (c_avl_iterator_next (iter, (void *) &key, (void *) &value) == 0)
 +  {
 +    /* remove missing values when list values */
 +    if (value->state == STATE_MISSING)
 +      continue;
 +
 +    /* c_avl_size does not return a number smaller than the number of elements
 +     * returned by c_avl_iterator_next. */
 +    assert (number < size_arrays);
 +
 +    if (ret_times != NULL)
 +      times[number] = value->last_time;
 +
 +    names[number] = strdup (key);
 +    if (names[number] == NULL)
 +    {
 +      status = -1;
 +      break;
 +    }
 +
 +    number++;
 +  } /* while (c_avl_iterator_next) */
 +
 +  c_avl_iterator_destroy (iter);
 +  pthread_mutex_unlock (&cache_lock);
 +
 +  if (status != 0)
 +  {
 +    size_t i;
-     
++
 +    for (i = 0; i < number; i++)
 +    {
 +      sfree (names[i]);
 +    }
 +    sfree (names);
++    sfree (times);
 +
 +    return (-1);
 +  }
 +
 +  *ret_names = names;
 +  if (ret_times != NULL)
 +    *ret_times = times;
++  else
++    sfree (times);
 +  *ret_number = number;
 +
 +  return (0);
 +} /* int uc_get_names */
 +
 +int uc_get_state (const data_set_t *ds, const value_list_t *vl)
 +{
 +  char name[6 * DATA_MAX_NAME_LEN];
 +  cache_entry_t *ce = NULL;
 +  int ret = STATE_ERROR;
 +
 +  if (FORMAT_VL (name, sizeof (name), vl) != 0)
 +  {
 +    ERROR ("uc_get_state: FORMAT_VL failed.");
 +    return (STATE_ERROR);
 +  }
 +
 +  pthread_mutex_lock (&cache_lock);
 +
 +  if (c_avl_get (cache_tree, name, (void *) &ce) == 0)
 +  {
 +    assert (ce != NULL);
 +    ret = ce->state;
 +  }
 +
 +  pthread_mutex_unlock (&cache_lock);
 +
 +  return (ret);
 +} /* int uc_get_state */
 +
 +int uc_set_state (const data_set_t *ds, const value_list_t *vl, int state)
 +{
 +  char name[6 * DATA_MAX_NAME_LEN];
 +  cache_entry_t *ce = NULL;
 +  int ret = -1;
 +
 +  if (FORMAT_VL (name, sizeof (name), vl) != 0)
 +  {
 +    ERROR ("uc_get_state: FORMAT_VL failed.");
 +    return (STATE_ERROR);
 +  }
 +
 +  pthread_mutex_lock (&cache_lock);
 +
 +  if (c_avl_get (cache_tree, name, (void *) &ce) == 0)
 +  {
 +    assert (ce != NULL);
 +    ret = ce->state;
 +    ce->state = state;
 +  }
 +
 +  pthread_mutex_unlock (&cache_lock);
 +
 +  return (ret);
 +} /* int uc_set_state */
 +
 +int uc_get_history_by_name (const char *name,
 +    gauge_t *ret_history, size_t num_steps, size_t num_ds)
 +{
 +  cache_entry_t *ce = NULL;
 +  size_t i;
 +  int status = 0;
 +
 +  pthread_mutex_lock (&cache_lock);
 +
 +  status = c_avl_get (cache_tree, name, (void *) &ce);
 +  if (status != 0)
 +  {
 +    pthread_mutex_unlock (&cache_lock);
 +    return (-ENOENT);
 +  }
 +
 +  if (((size_t) ce->values_num) != num_ds)
 +  {
 +    pthread_mutex_unlock (&cache_lock);
 +    return (-EINVAL);
 +  }
 +
 +  /* Check if there are enough values available. If not, increase the buffer
 +   * size. */
 +  if (ce->history_length < num_steps)
 +  {
 +    gauge_t *tmp;
 +    size_t i;
 +
 +    tmp = realloc (ce->history, sizeof (*ce->history)
 +	* num_steps * ce->values_num);
 +    if (tmp == NULL)
 +    {
 +      pthread_mutex_unlock (&cache_lock);
 +      return (-ENOMEM);
 +    }
 +
 +    for (i = ce->history_length * ce->values_num;
 +	i < (num_steps * ce->values_num);
 +	i++)
 +      tmp[i] = NAN;
 +
 +    ce->history = tmp;
 +    ce->history_length = num_steps;
 +  } /* if (ce->history_length < num_steps) */
 +
 +  /* Copy the values to the output buffer. */
 +  for (i = 0; i < num_steps; i++)
 +  {
 +    size_t src_index;
 +    size_t dst_index;
 +
 +    if (i < ce->history_index)
 +      src_index = ce->history_index - (i + 1);
 +    else
 +      src_index = ce->history_length + ce->history_index - (i + 1);
 +    src_index = src_index * num_ds;
 +
 +    dst_index = i * num_ds;
 +
 +    memcpy (ret_history + dst_index, ce->history + src_index,
 +	sizeof (*ret_history) * num_ds);
 +  }
 +
 +  pthread_mutex_unlock (&cache_lock);
 +
 +  return (0);
 +} /* int uc_get_history_by_name */
 +
 +int uc_get_history (const data_set_t *ds, const value_list_t *vl,
 +    gauge_t *ret_history, size_t num_steps, size_t num_ds)
 +{
 +  char name[6 * DATA_MAX_NAME_LEN];
 +
 +  if (FORMAT_VL (name, sizeof (name), vl) != 0)
 +  {
 +    ERROR ("utils_cache: uc_get_history: FORMAT_VL failed.");
 +    return (-1);
 +  }
 +
 +  return (uc_get_history_by_name (name, ret_history, num_steps, num_ds));
 +} /* int uc_get_history */
 +
 +int uc_get_hits (const data_set_t *ds, const value_list_t *vl)
 +{
 +  char name[6 * DATA_MAX_NAME_LEN];
 +  cache_entry_t *ce = NULL;
 +  int ret = STATE_ERROR;
 +
 +  if (FORMAT_VL (name, sizeof (name), vl) != 0)
 +  {
 +    ERROR ("uc_get_state: FORMAT_VL failed.");
 +    return (STATE_ERROR);
 +  }
 +
 +  pthread_mutex_lock (&cache_lock);
 +
 +  if (c_avl_get (cache_tree, name, (void *) &ce) == 0)
 +  {
 +    assert (ce != NULL);
 +    ret = ce->hits;
 +  }
 +
 +  pthread_mutex_unlock (&cache_lock);
 +
 +  return (ret);
 +} /* int uc_get_hits */
 +
 +int uc_set_hits (const data_set_t *ds, const value_list_t *vl, int hits)
 +{
 +  char name[6 * DATA_MAX_NAME_LEN];
 +  cache_entry_t *ce = NULL;
 +  int ret = -1;
 +
 +  if (FORMAT_VL (name, sizeof (name), vl) != 0)
 +  {
 +    ERROR ("uc_get_state: FORMAT_VL failed.");
 +    return (STATE_ERROR);
 +  }
 +
 +  pthread_mutex_lock (&cache_lock);
 +
 +  if (c_avl_get (cache_tree, name, (void *) &ce) == 0)
 +  {
 +    assert (ce != NULL);
 +    ret = ce->hits;
 +    ce->hits = hits;
 +  }
 +
 +  pthread_mutex_unlock (&cache_lock);
 +
 +  return (ret);
 +} /* int uc_set_hits */
 +
 +int uc_inc_hits (const data_set_t *ds, const value_list_t *vl, int step)
 +{
 +  char name[6 * DATA_MAX_NAME_LEN];
 +  cache_entry_t *ce = NULL;
 +  int ret = -1;
 +
 +  if (FORMAT_VL (name, sizeof (name), vl) != 0)
 +  {
 +    ERROR ("uc_get_state: FORMAT_VL failed.");
 +    return (STATE_ERROR);
 +  }
 +
 +  pthread_mutex_lock (&cache_lock);
 +
 +  if (c_avl_get (cache_tree, name, (void *) &ce) == 0)
 +  {
 +    assert (ce != NULL);
 +    ret = ce->hits;
 +    ce->hits = ret + step;
 +  }
 +
 +  pthread_mutex_unlock (&cache_lock);
 +
 +  return (ret);
 +} /* int uc_inc_hits */
 +
 +/*
 + * Meta data interface
 + */
 +/* XXX: This function will acquire `cache_lock' but will not free it! */
 +static meta_data_t *uc_get_meta (const value_list_t *vl) /* {{{ */
 +{
 +  char name[6 * DATA_MAX_NAME_LEN];
 +  cache_entry_t *ce = NULL;
 +  int status;
 +
 +  status = FORMAT_VL (name, sizeof (name), vl);
 +  if (status != 0)
 +  {
 +    ERROR ("utils_cache: uc_get_meta: FORMAT_VL failed.");
 +    return (NULL);
 +  }
 +
 +  pthread_mutex_lock (&cache_lock);
 +
 +  status = c_avl_get (cache_tree, name, (void *) &ce);
 +  if (status != 0)
 +  {
 +    pthread_mutex_unlock (&cache_lock);
 +    return (NULL);
 +  }
 +  assert (ce != NULL);
 +
 +  if (ce->meta == NULL)
 +    ce->meta = meta_data_create ();
 +
 +  if (ce->meta == NULL)
 +    pthread_mutex_unlock (&cache_lock);
 +
 +  return (ce->meta);
 +} /* }}} meta_data_t *uc_get_meta */
 +
 +/* Sorry about this preprocessor magic, but it really makes this file much
 + * shorter.. */
 +#define UC_WRAP(wrap_function) { \
 +  meta_data_t *meta; \
 +  int status; \
 +  meta = uc_get_meta (vl); \
 +  if (meta == NULL) return (-1); \
 +  status = wrap_function (meta, key); \
 +  pthread_mutex_unlock (&cache_lock); \
 +  return (status); \
 +}
 +int uc_meta_data_exists (const value_list_t *vl, const char *key)
 +  UC_WRAP (meta_data_exists)
 +
 +int uc_meta_data_delete (const value_list_t *vl, const char *key)
 +  UC_WRAP (meta_data_delete)
 +#undef UC_WRAP
 +
 +/* We need a new version of this macro because the following functions take
 + * two argumetns. */
 +#define UC_WRAP(wrap_function) { \
 +  meta_data_t *meta; \
 +  int status; \
 +  meta = uc_get_meta (vl); \
 +  if (meta == NULL) return (-1); \
 +  status = wrap_function (meta, key, value); \
 +  pthread_mutex_unlock (&cache_lock); \
 +  return (status); \
 +}
 +int uc_meta_data_add_string (const value_list_t *vl,
 +    const char *key,
 +    const char *value)
 +  UC_WRAP(meta_data_add_string)
 +int uc_meta_data_add_signed_int (const value_list_t *vl,
 +    const char *key,
 +    int64_t value)
 +  UC_WRAP(meta_data_add_signed_int)
 +int uc_meta_data_add_unsigned_int (const value_list_t *vl,
 +    const char *key,
 +    uint64_t value)
 +  UC_WRAP(meta_data_add_unsigned_int)
 +int uc_meta_data_add_double (const value_list_t *vl,
 +    const char *key,
 +    double value)
 +  UC_WRAP(meta_data_add_double)
 +int uc_meta_data_add_boolean (const value_list_t *vl,
 +    const char *key,
 +    _Bool value)
 +  UC_WRAP(meta_data_add_boolean)
 +
 +int uc_meta_data_get_string (const value_list_t *vl,
 +    const char *key,
 +    char **value)
 +  UC_WRAP(meta_data_get_string)
 +int uc_meta_data_get_signed_int (const value_list_t *vl,
 +    const char *key,
 +    int64_t *value)
 +  UC_WRAP(meta_data_get_signed_int)
 +int uc_meta_data_get_unsigned_int (const value_list_t *vl,
 +    const char *key,
 +    uint64_t *value)
 +  UC_WRAP(meta_data_get_unsigned_int)
 +int uc_meta_data_get_double (const value_list_t *vl,
 +    const char *key,
 +    double *value)
 +  UC_WRAP(meta_data_get_double)
 +int uc_meta_data_get_boolean (const value_list_t *vl,
 +    const char *key,
 +    _Bool *value)
 +  UC_WRAP(meta_data_get_boolean)
 +#undef UC_WRAP
 +
 +/* vim: set sw=2 ts=8 sts=2 tw=78 : */
diff --cc src/threshold.c
index a8900db7,391ee932..8dcb711d
--- a/src/threshold.c
+++ b/src/threshold.c
@@@ -512,13 -622,9 +512,12 @@@ static int ut_report_state (const data_
    if (state == STATE_OKAY)
    {
      if (state_old == STATE_MISSING)
-       status = ssnprintf (buf, bufsize,
-           ": Value is no longer missing.");
+       ssnprintf (buf, bufsize, ": Value is no longer missing.");
      else
-       status = ssnprintf (buf, bufsize,
 -      ssnprintf (buf, bufsize, ": All data sources are within range again.");
++      ssnprintf (buf, bufsize,
 +          ": All data sources are within range again. "
 +          "Current value of \"%s\" is %f.",
 +          ds->ds[ds_index].name, values[ds_index]);
    }
    else
    {