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Latency: low level time series analysis implemented.

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This commit is contained in:
antirez 2014-07-07 14:59:57 +02:00
parent b2604dc58c
commit 19853db892
2 changed files with 60 additions and 0 deletions
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50
src/latency.c
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@ -122,6 +122,56 @@ int latencyResetEvent(char *event_to_reset) {
return resets;
}
/* ------------------------ Latency reporting (doctor) ---------------------- */
/* Analyze the samples avaialble for a given event and return a structure
* populate with different metrics, average, MAD, min, max, and so forth.
* Check latency.h definition of struct latenctStat for more info.
* If the specified event has no elements the structure is populate with
* zero values. */
void analyzeLatencyForEvent(char *event, struct latencyStats *ls) {
struct latencyTimeSeries *ts = dictFetchValue(server.latency_events,event);
int j;
uint64_t sum;
ls->all_time_high = ts ? ts->max : 0;
ls->avg = 0;
ls->min = 0;
ls->max = 0;
ls->mad = 0;
ls->samples = 0;
if (!ts) return;
/* First pass, populate everything but the MAD. */
sum = 0;
for (j = 0; j < LATENCY_TS_LEN; j++) {
if (ts->samples[j].time == 0) continue;
ls->samples++;
if (ls->samples == 1) {
ls->min = ls->max = ts->samples[j].latency;
} else {
if (ls->min > ts->samples[j].latency)
ls->min = ts->samples[j].latency;
if (ls->max < ts->samples[j].latency)
ls->max = ts->samples[j].latency;
}
sum += ts->samples[j].latency;
}
if (ls->samples) ls->avg = sum / ls->samples;
/* Second pass, compute MAD. */
sum = 0;
for (j = 0; j < LATENCY_TS_LEN; j++) {
int64_t delta;
if (ts->samples[j].time == 0) continue;
delta = ls->avg - ts->samples[j].latency;
if (delta < 0) delta = -delta;
sum += delta;
}
if (ls->samples) ls->mad = sum / ls->samples;
}
/* ---------------------- Latency command implementation -------------------- */
/* latencyCommand() helper to produce a time-delay reply for all the samples

10
src/latency.h
View File

@ -50,6 +50,16 @@ struct latencyTimeSeries {
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. */
};
void latencyMonitorInit(void);
void latencyAddSample(char *event, mstime_t latency);