When the C<rrdtool> plugin uses a cache (by setting B<CacheTimeout>, see below)
it writes all values for a certain RRD-file if the oldest value is older than
-(or equal to) the number of seconds specified. If some RRD-file is not updated
+(or equal to) the number of seconds specified by B<CacheTimeout>.
+That check happens on new values arriwal. If some RRD-file is not updated
anymore for some reason (the computer was shut down, the network is broken,
-etc.) some values may still be in the cache. If B<CacheFlush> is set, then the
-entire cache is searched for entries older than B<CacheTimeout> seconds and
-written to disk every I<Seconds> seconds. Since this is kind of expensive and
-does nothing under normal circumstances, this value should not be too small.
-900 seconds might be a good value, though setting this to 7200 seconds doesn't
-normally do much harm either.
+etc.) some values may still be in the cache. If B<CacheFlush> is set, then
+every I<Seconds> seconds the entire cache is searched for entries older than
+B<CacheTimeout> + B<RandomTimeout> seconds. The entries found are written to
+disk. Since scanning the entire cache is kind of expensive and does nothing
+under normal circumstances, this value should not be too small. 900 seconds
+might be a good value, though setting this to 7200 seconds doesn't normally
+do much harm either.
+
+Defaults to 10x B<CacheTimeout>.
+B<CacheFlush> must be larger than or equal to B<CacheTimeout>, otherwise the
+above default is used.
=item B<CacheTimeout> I<Seconds>
* ALWAYS lock `cache_lock' first! */
static cdtime_t cache_timeout = 0;
static cdtime_t cache_flush_timeout = 0;
-static cdtime_t random_timeout = TIME_T_TO_CDTIME_T_STATIC(1);
+static cdtime_t random_timeout = 0;
static cdtime_t cache_flush_last;
static c_avl_tree_t *cache = NULL;
static pthread_mutex_t cache_lock = PTHREAD_MUTEX_INITIALIZER;
CDTIME_T_TO_DOUBLE(timeout));
now = cdtime();
- timeout = TIME_T_TO_CDTIME_T(timeout);
/* Build a list of entries to be flushed */
iter = c_avl_get_iterator(cache);
} /* int rrd_cache_flush_identifier */
static int64_t rrd_get_random_variation(void) {
- long min;
- long max;
-
if (random_timeout == 0)
return (0);
- /* Assure that "cache_timeout + random_variation" is never negative. */
- if (random_timeout > cache_timeout) {
- INFO("rrdtool plugin: Adjusting \"RandomTimeout\" to %.3f seconds.",
- CDTIME_T_TO_DOUBLE(cache_timeout));
- random_timeout = cache_timeout;
- }
-
- max = (long)(random_timeout / 2);
- min = max - ((long)random_timeout);
-
- return ((int64_t)cdrand_range(min, max));
+ return (int64_t)cdrand_range(-random_timeout, random_timeout);
} /* int64_t rrd_get_random_variation */
static int rrd_cache_insert(const char *filename, const char *value,
if ((cache_timeout > 0) &&
((cdtime() - cache_flush_last) > cache_flush_timeout))
- rrd_cache_flush(cache_flush_timeout);
+ rrd_cache_flush(cache_timeout + random_timeout);
pthread_mutex_unlock(&cache_lock);
}
cache_timeout = DOUBLE_TO_CDTIME_T(tmp);
} else if (strcasecmp("CacheFlush", key) == 0) {
- int tmp = atoi(value);
+ double tmp = atof(value);
if (tmp < 0) {
fprintf(stderr, "rrdtool: `CacheFlush' must "
"be greater than 0.\n");
"be greater than 0.\n");
return (1);
}
- cache_flush_timeout = tmp;
+ cache_flush_timeout = DOUBLE_TO_CDTIME_T(tmp);
} else if (strcasecmp("DataDir", key) == 0) {
char *tmp;
size_t len;
cache_flush_last = cdtime();
if (cache_timeout == 0) {
+ random_timeout = 0;
cache_flush_timeout = 0;
- } else if (cache_flush_timeout < cache_timeout)
+ } else if (cache_flush_timeout < cache_timeout) {
+ INFO("rrdtool plugin: \"CacheFlush %.3f\" is less than \"CacheTimeout %.3f\". "
+ "Ajusting \"CacheFlush\" to %.3f seconds.",
+ CDTIME_T_TO_DOUBLE(cache_flush_timeout),
+ CDTIME_T_TO_DOUBLE(cache_timeout),
+ CDTIME_T_TO_DOUBLE(cache_timeout * 10));
cache_flush_timeout = 10 * cache_timeout;
+ }
+
+ /* Assure that "cache_timeout + random_variation" is never negative. */
+ if (random_timeout > cache_timeout) {
+ INFO("rrdtool plugin: Adjusting \"RandomTimeout\" to %.3f seconds.",
+ CDTIME_T_TO_DOUBLE(cache_timeout));
+ random_timeout = cache_timeout;
+ }
pthread_mutex_unlock(&cache_lock);