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/* latency.h -- latency monitor API header file
* See latency.c for more information.
*
* ----------------------------------------------------------------------------
*
* 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.
*/
#ifndef __LATENCY_H
#define __LATENCY_H
#define LATENCY_TS_LEN 160 /* History length for every monitored event. */
/* Representation of a latency sample: the sampling time and the latency
* observed in milliseconds. */
struct latencySample {
int32_t time; /* We don't use time_t to force 4 bytes usage everywhere. */
uint32_t latency; /* Latency in milliseconds. */
};
/* The latency time series for a given event. */
struct latencyTimeSeries {
int idx; /* Index of the next sample to store. */
uint32_t max; /* Max latency observed for this event. */
struct latencySample samples[LATENCY_TS_LEN]; /* Latest history. */
};
/* Latency statistics structure. */
struct latencyStats {
uint32_t all_time_high; /* Absolute max observed since latest reset. */
uint32_t avg; /* Average of current samples. */
uint32_t min; /* Min of current samples. */
uint32_t max; /* Max of current samples. */
uint32_t mad; /* Mean absolute deviation. */
uint32_t samples; /* Number of non-zero samples. */
time_t period; /* Number of seconds since first event and now. */
};
void latencyMonitorInit(void);
void latencyAddSample(char *event, mstime_t latency);
/* Latency monitoring macros. */
/* Start monitoring an event. We just set the current time. */
#define latencyStartMonitor(var) if (server.latency_monitor_threshold) { \
var = mstime(); \
} else { \
var = 0; \
}
/* End monitoring an event, compute the difference with the current time
* to check the amount of time elapsed. */
#define latencyEndMonitor(var) if (server.latency_monitor_threshold) { \
var = mstime() - var; \
}
/* Add the sample only if the elapsed time is >= to the configured threshold. */
#define latencyAddSampleIfNeeded(event,var) \
if (server.latency_monitor_threshold && \
(var) >= server.latency_monitor_threshold) \
latencyAddSample((event),(var));
#endif /* __LATENCY_H */
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