Function createLatencyReport

src/latency.cpp:234–489

Create a human readable report of latency events for this KeyDB instance. */

/* Create a human readable report of latency events for this KeyDB instance. */
sds createLatencyReport(void) {
    sds report = sdsempty();
    int advise_better_vm = 0;       /* Better virtual machines. */
    int advise_slowlog_enabled = 0; /* Enable slowlog. */
    int advise_slowlog_tuning = 0;  /* Reconfigure slowlog. */
    int advise_slowlog_inspect = 0; /* Check your slowlog. */
    int advise_disk_contention = 0; /* Try to lower disk contention. */
    int advise_scheduler = 0;       /* Intrinsic latency. */
    int advise_data_writeback = 0;  /* data=writeback. */
    int advise_no_appendfsync = 0;  /* don't fsync during rewrites. */
    int advise_local_disk = 0;      /* Avoid remote disks. */
    int advise_ssd = 0;             /* Use an SSD drive. */
    int advise_write_load_info = 0; /* Print info about AOF and write load. */
    int advise_hz = 0;              /* Use higher HZ. */
    int advise_large_objects = 0;   /* Deletion of large objects. */
    int advise_mass_eviction = 0;   /* Avoid mass eviction of keys. */
    int advise_relax_fsync_policy = 0; /* appendfsync always is slow. */
    int advise_disable_thp = 0;     /* AnonHugePages detected. */
    int advices = 0;

    /* Return ASAP if the latency engine is disabled and it looks like it
     * was never enabled so far. */
    if (dictSize(g_pserver->latency_events) == 0 &&
        g_pserver->latency_monitor_threshold == 0)
    {
        report = sdscat(report,"I'm sorry, Dave, I can't do that. Latency monitoring is disabled in this KeyDB instance. You may use \"CONFIG SET latency-monitor-threshold <milliseconds>.\" in order to enable it.\n");
        return report;
    }

    /* Show all the events stats and add for each event some event-related
     * comment depending on the values. */
    dictIterator *di;
    dictEntry *de;
    int eventnum = 0;

    di = dictGetSafeIterator(g_pserver->latency_events);
    while((de = dictNext(di)) != NULL) {
        char *event = (char*)dictGetKey(de);
        struct latencyTimeSeries *ts = (latencyTimeSeries*)dictGetVal(de);
        struct latencyStats ls;

        if (ts == NULL) continue;
        eventnum++;
        if (eventnum == 1) {
            report = sdscat(report,"Dave, I have observed latency spikes in this KeyDB instance. You don't mind talking about it, do you Dave?\n\n");
        }
        analyzeLatencyForEvent(event,&ls);

        report = sdscatprintf(report,
            "%d. %s: %d latency spikes (average %lums, mean deviation %lums, period %.2f sec). Worst all time event %lums.",
            eventnum, event,
            ls.samples,
            (unsigned long) ls.avg,
            (unsigned long) ls.mad,
            (double) ls.period/ls.samples,
            (unsigned long) ts->max);

        /* Fork */