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/* The latency monitor allows to easily observe the sources of latency
* in a Redis instance using the LATENCY command. Different latency
* sources are monitored, like disk I/O, execution of commands, fork
* system call, and so forth.
*
* ----------------------------------------------------------------------------
*
* Copyright (c) 2014, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "redis.h"
/* Dictionary type for latency events. Key/Val destructors are set to NULL
* since we never delete latency time series at runtime. */
int dictStringKeyCompare(void *privdata, const void *key1, const void *key2) {
return strcmp(key1,key2) == 0;
}
unsigned int dictStringHash(const void *key) {
return dictGenHashFunction(key, strlen(key));
}
dictType latencyTimeSeriesDictType = {
dictStringHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictStringKeyCompare, /* key compare */
NULL, /* key destructor */
NULL /* val destructor */
};
/* ---------------------------- Latency API --------------------------------- */
/* Latency monitor initialization. We just need to create the dictionary
* of time series, each time serie is craeted on demand in order to avoid
* having a fixed list to maintain. */
void latencyMonitorInit(void) {
server.latency_events = dictCreate(&latencyTimeSeriesDictType,NULL);
}
/* Add the specified sample to the specified time series "event".
* This function is usually called via latencyAddSampleIfNeeded(), that
* is a macro that only adds the sample if the latency is higher than
* server.latency_monitor_threshold. */
void latencyAddSample(char *event, mstime_t latency) {
struct latencyTimeSeries *ts = dictFetchValue(server.latency_events,event);
time_t now = time(NULL);
int prev;
/* Create the time series if it does not exist. */
if (ts == NULL) {
ts = zmalloc(sizeof(*ts));
ts->idx = 0;
ts->max = 0;
memset(ts->samples,0,sizeof(ts->samples));
dictAdd(server.latency_events,zstrdup(event),ts);
}
/* If the previous sample is in the same second, we update our old sample
* if this latency is > of the old one, or just return. */
prev = (ts->idx + LATENCY_TS_LEN - 1) % LATENCY_TS_LEN;
if (ts->samples[prev].time == now) {
if (latency > ts->samples[prev].latency)
ts->samples[prev].latency = latency;
return;
}
ts->samples[ts->idx].time = time(NULL);
ts->samples[ts->idx].latency = latency;
if (latency > ts->max) ts->max = latency;
ts->idx++;
if (ts->idx == LATENCY_TS_LEN) ts->idx = 0;
}
/* ---------------------- Latency command implementation -------------------- */
/* latencyCommand() helper to produce a time-delay reply for all the samples
* in memory for the specified time series. */
void latencyCommandReplyWithSamples(redisClient *c, struct latencyTimeSeries *ts) {
void *replylen = addDeferredMultiBulkLength(c);
int samples = 0, j;
for (j = 0; j < LATENCY_TS_LEN; j++) {
int i = (ts->idx + j) % LATENCY_TS_LEN;
if (ts->samples[i].time == 0) continue;
addReplyMultiBulkLen(c,2);
addReplyLongLong(c,ts->samples[i].time);
addReplyLongLong(c,ts->samples[i].latency);
samples++;
}
setDeferredMultiBulkLength(c,replylen,samples);
}
/* latencyCommand() helper to produce the reply for the LATEST subcommand,
* listing the last latency sample for every event type registered so far. */
void latencyCommandReplyWithLatestEvents(redisClient *c) {
dictIterator *di;
dictEntry *de;
addReplyMultiBulkLen(c,dictSize(server.latency_events));
di = dictGetIterator(server.latency_events);
while((de = dictNext(di)) != NULL) {
char *event = dictGetKey(de);
struct latencyTimeSeries *ts = dictGetVal(de);
int last = (ts->idx + LATENCY_TS_LEN - 1) % LATENCY_TS_LEN;
addReplyMultiBulkLen(c,3);
addReplyBulkCString(c,event);
addReplyLongLong(c,ts->samples[last].time);
addReplyLongLong(c,ts->samples[last].latency);
}
dictReleaseIterator(di);
}
/* LATENCY command implementations.
*
* LATENCY SAMPLES: return time-latency samples for the specified event.
* LATENCY LATEST: return the latest latency for all the events classes.
* LATENCY DOCTOR: returns an human readable analysis of instance latency.
* LATENCY GRAPH: provide an ASCII graph of the latency of the specified event.
*/
void latencyCommand(redisClient *c) {
struct latencyTimeSeries *ts;
if (!strcasecmp(c->argv[1]->ptr,"samples") && c->argc == 3) {
/* LATENCY SAMPLES <event> */
ts = dictFetchValue(server.latency_events,c->argv[2]->ptr);
if (ts == NULL) goto nodataerr;
latencyCommandReplyWithSamples(c,ts);
} else if (!strcasecmp(c->argv[1]->ptr,"latest") && c->argc == 2) {
/* LATENCY LATEST */
latencyCommandReplyWithLatestEvents(c);
} else {
addReply(c,shared.syntaxerr);
return;
}
return;
nodataerr:
/* Common error when the user asks for an event we have no latency
* information about. */
addReplyErrorFormat(c,
"No samples available for event '%s'", c->argv[2]->ptr);
}
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