lib/storage: add ability to change the indexdb rotation time offset with -retentionTimezoneOffset command-line flag

This is a follow-up for 0fbf59199a

See https://github.com/VictoriaMetrics/VictoriaMetrics/pull/2574

app/vmstorage/main.go

@@ -37,9 +37,12 @@ var (
 	finalMergeDelay = flag.Duration("finalMergeDelay", 0, "The delay before starting final merge for per-month partition after no new data is ingested into it. "+
 		"Final merge may require additional disk IO and CPU resources. Final merge may increase query speed and reduce disk space usage in some cases. "+
 		"Zero value disables final merge")
-	bigMergeConcurrency   = flag.Int("bigMergeConcurrency", 0, "The maximum number of CPU cores to use for big merges. Default value is used if set to 0")
-	smallMergeConcurrency = flag.Int("smallMergeConcurrency", 0, "The maximum number of CPU cores to use for small merges. Default value is used if set to 0")
-	minScrapeInterval     = flag.Duration("dedup.minScrapeInterval", 0, "Leave only the last sample in every time series per each discrete interval "+
+	bigMergeConcurrency     = flag.Int("bigMergeConcurrency", 0, "The maximum number of CPU cores to use for big merges. Default value is used if set to 0")
+	smallMergeConcurrency   = flag.Int("smallMergeConcurrency", 0, "The maximum number of CPU cores to use for small merges. Default value is used if set to 0")
+	retentionTimezoneOffset = flag.Duration("retentionTimezoneOffset", 0, "The offset for performing indexdb rotation. "+
+		"If set to 0, then the indexdb rotation is performed at 4am UTC time per each -retentionPeriod. "+
+		"If set to 2h, then the indexdb rotation is performed at 4am EET time (the timezone with +2h offset)")
+	minScrapeInterval = flag.Duration("dedup.minScrapeInterval", 0, "Leave only the last sample in every time series per each discrete interval "+
 		"equal to -dedup.minScrapeInterval > 0. See https://docs.victoriametrics.com/#deduplication for details")
 
 	logNewSeries = flag.Bool("logNewSeries", false, "Whether to log new series. This option is for debug purposes only. It can lead to performance issues "+
@@ -69,6 +72,7 @@ func main() {
 	storage.SetFinalMergeDelay(*finalMergeDelay)
 	storage.SetBigMergeWorkersCount(*bigMergeConcurrency)
 	storage.SetSmallMergeWorkersCount(*smallMergeConcurrency)
+	storage.SetRetentionTimezoneOffset(*retentionTimezoneOffset)
 	storage.SetFreeDiskSpaceLimit(minFreeDiskSpaceBytes.N)
 	storage.SetTSIDCacheSize(cacheSizeStorageTSID.N)
 	mergeset.SetIndexBlocksCacheSize(cacheSizeIndexDBIndexBlocks.N)

docs/CHANGELOG.md

@@ -16,6 +16,7 @@ The following tip changes can be tested by building VictoriaMetrics components f
 ## tip
 
 * FEATURE: [vmagent](https://docs.victoriametrics.com/vmagent.html): expose `/api/v1/status/config` endpoint in the same way as Prometheus does. See [these docs](https://prometheus.io/docs/prometheus/latest/querying/api/#config).
+* FEATURE: add ability to change the `indexdb` rotation timezone offset via `-retentionTimezoneOffset` command-line flag. Previously it was performed at 4am UTC time. This could lead to performance degradation in the middle of the day when VictoriaMetrics runs in time zones located too far from UTC. Thanks to @cnych for [the pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/2574).
 
 * BUGFIX: [vmalert](https://docs.victoriametrics.com/vmalert.html): properly apply `alert_relabel_configs` relabeling rules to `-notifier.config` according to [these docs](https://docs.victoriametrics.com/vmalert.html#notifier-configuration-file). Thanks to @spectvtor for [the bugfix](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/2633).
 

lib/storage/storage.go

@@ -1098,19 +1098,26 @@ func (s *Storage) mustSaveCache(c *workingsetcache.Cache, info, name string) {
 // saveCacheLock prevents from data races when multiple concurrent goroutines save the same cache.
 var saveCacheLock sync.Mutex
 
+// SetRetentionTimezoneOffset sets the offset, which is used for calculating the time for indexdb rotation.
+// See https://github.com/VictoriaMetrics/VictoriaMetrics/pull/2574
+func SetRetentionTimezoneOffset(offset time.Duration) {
+	retentionTimezoneOffsetMsecs = offset.Milliseconds()
+}
+
+var retentionTimezoneOffsetMsecs int64
+
 func nextRetentionDuration(retentionMsecs int64) time.Duration {
 	// Round retentionMsecs to days. This guarantees that per-day inverted index works as expected.
 	retentionMsecs = ((retentionMsecs + msecPerDay - 1) / msecPerDay) * msecPerDay
-	now := time.Now()
-	t := now.UnixNano() / 1e6
+	t := time.Now().UnixNano() / 1e6
 	deadline := ((t + retentionMsecs - 1) / retentionMsecs) * retentionMsecs
 	// Schedule the deadline to +4 hours from the next retention period start.
 	// This should prevent from possible double deletion of indexdb
 	// due to time drift - see https://github.com/VictoriaMetrics/VictoriaMetrics/issues/248 .
 	deadline += 4 * 3600 * 1000
-	// The effect of time zone on retention period is moved out
-	_, offset := now.Zone()
-	deadline -= int64(offset) * 1000
+	// The effect of time zone on retention period is moved out.
+	// See https://github.com/VictoriaMetrics/VictoriaMetrics/pull/2574
+	deadline -= retentionTimezoneOffsetMsecs
 	return time.Duration(deadline-t) * time.Millisecond
 }