app/victoria-metrics: automatically reset response cache when samples with too timestamps older than now - search.cacheTimestampOffset are ingested

docs/CHANGELOG.md

@@ -2,6 +2,7 @@
 
 # tip
 
+* FEATURE: automatically reset response cache when samples with timestamps older than `now - search.cacheTimestampOffset` are ingested to VictoriaMetrics. This makes unnecessary disabling response cache during data backfilling or resetting it after backfilling is complete as described [in these docs](https://victoriametrics.github.io/#backfilling). This feature applies only to single-node VictoriaMetrics. It doesn't apply to cluster version of VictoriaMetrics because `vminsert` nodes don't know about `vmselect` nodes where the response cache must be reset.
 * FEATURE: allow multiple whitespace chars between measurements, fields and timestamp when parsing InfluxDB line protocol.
   Though [InfluxDB line protocol](https://docs.influxdata.com/influxdb/v1.8/write_protocols/line_protocol_tutorial/) denies multiple whitespace chars between these entities,
   some apps improperly put multiple whitespace chars. This workaround allows accepting data from such apps.

docs/Single-server-VictoriaMetrics.md

@@ -1332,7 +1332,8 @@ An alternative solution is to query `/internal/resetRollupResultCache` url after
 the query cache, which could contain incomplete data cached during the backfilling.
 
 Yet another solution is to increase `-search.cacheTimestampOffset` flag value in order to disable caching
-for data with timestamps close to the current time.
+for data with timestamps close to the current time. Single-node VictoriaMetrics automatically resets response
+cache when samples with timestamps older than `now - search.cacheTimestampOffset` are ingested to it.
 
 
 ## Data updates