1/* latency.h -- latency monitor API header file
2 * See latency.c for more information.
3 *
4 * ----------------------------------------------------------------------------
5 *
6 * Copyright (c) 2014, Salvatore Sanfilippo <antirez at gmail dot com>
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions are met:
11 *
12 * * Redistributions of source code must retain the above copyright notice,
13 * this list of conditions and the following disclaimer.
14 * * Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * * Neither the name of Redis nor the names of its contributors may be used
18 * to endorse or promote products derived from this software without
19 * specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
22 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
25 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
26 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
27 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
28 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
29 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
30 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
31 * POSSIBILITY OF SUCH DAMAGE.
32 */
33
34#ifndef __LATENCY_H
35#define __LATENCY_H
36
37#define LATENCY_TS_LEN 160 /* History length for every monitored event. */
38
39/* Representation of a latency sample: the sampling time and the latency
40 * observed in milliseconds. */
41struct latencySample {
42 int32_t time; /* We don't use time_t to force 4 bytes usage everywhere. */
43 uint32_t latency; /* Latency in milliseconds. */
44};
45
46/* The latency time series for a given event. */
47struct latencyTimeSeries {
48 int idx; /* Index of the next sample to store. */
49 uint32_t max; /* Max latency observed for this event. */
50 struct latencySample samples[LATENCY_TS_LEN]; /* Latest history. */
51};
52
53/* Latency statistics structure. */
54struct latencyStats {
55 uint32_t all_time_high; /* Absolute max observed since latest reset. */
56 uint32_t avg; /* Average of current samples. */
57 uint32_t min; /* Min of current samples. */
58 uint32_t max; /* Max of current samples. */
59 uint32_t mad; /* Mean absolute deviation. */
60 uint32_t samples; /* Number of non-zero samples. */
61 time_t period; /* Number of seconds since first event and now. */
62};
63
64void latencyMonitorInit(void);
65void latencyAddSample(const char *event, mstime_t latency);
66
67/* Latency monitoring macros. */
68
69/* Start monitoring an event. We just set the current time. */
70#define latencyStartMonitor(var) if (server.latency_monitor_threshold) { \
71 var = mstime(); \
72} else { \
73 var = 0; \
74}
75
76/* End monitoring an event, compute the difference with the current time
77 * to check the amount of time elapsed. */
78#define latencyEndMonitor(var) if (server.latency_monitor_threshold) { \
79 var = mstime() - var; \
80}
81
82/* Add the sample only if the elapsed time is >= to the configured threshold. */
83#define latencyAddSampleIfNeeded(event,var) \
84 if (server.latency_monitor_threshold && \
85 (var) >= server.latency_monitor_threshold) \
86 latencyAddSample((event),(var));
87
88/* Remove time from a nested event. */
89#define latencyRemoveNestedEvent(event_var,nested_var) \
90 event_var += nested_var;
91
92#endif /* __LATENCY_H */
93