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. */ 41 struct 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. */ 47 struct 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. */ 54 struct 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 64 void latencyMonitorInit(void); 65 void latencyAddSample(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 #endif /* __LATENCY_H */ 89