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Co-authored-by: cubic-dev-ai[bot] <191113872+cubic-dev-ai[bot]@users.noreply.github.com>
Signed-off-by: Max Kotliar <kotlyar.maksim@gmail.com>

docs/victoriametrics/Cluster-VictoriaMetrics.md

@@ -700,6 +700,7 @@ Also in the cluster version the `/prometheus/api/v1` endpoint ingests  `jsonl`,
 
 - `vmstorage` nodes provide the following HTTP endpoints on `8482` port:
   - `/internal/force_merge` - initiate [forced compactions](https://docs.victoriametrics.com/victoriametrics/single-server-victoriametrics/#forced-merge) on the given `vmstorage` node.
+  - `/internal/force_flush` - [flush in-memory buffers](https://docs.victoriametrics.com/victoriametrics/single-server-victoriametrics/#forced-flush) for recently ingested samples into searchable parts on the given `vmstorage` node.
   - `/snapshot/create` - create [instant snapshot](https://medium.com/@valyala/how-victoriametrics-makes-instant-snapshots-for-multi-terabyte-time-series-data-e1f3fb0e0282),
     which can be used for backups in background. Snapshots are created in `<storageDataPath>/snapshots` folder, where `<storageDataPath>` is the corresponding
     command-line flag value.

docs/victoriametrics/README.md

@@ -701,11 +701,11 @@ It's better to use the `-retentionPeriod` command-line flag for efficient prunin
 
 ## Forced merge
 
-VictoriaMetrics performs [data compactions in background](https://medium.com/@valyala/how-victoriametrics-makes-instant-snapshots-for-multi-terabyte-time-series-data-e1f3fb0e0282)
-in order to keep good performance characteristics when accepting new data. These compactions (merges) are performed independently on per-month partitions.
-This means that compactions are stopped for per-month partitions if no new data is ingested into these partitions.
-Sometimes it is necessary to trigger compactions for old partitions. For instance, in order to free up disk space occupied by [deleted time series](#how-to-delete-time-series).
-In this case forced compaction may be initiated on the specified per-month partition by sending request to `/internal/force_merge?partition_prefix=YYYY_MM`,
+VictoriaMetrics performs [data compaction in background](https://medium.com/@valyala/how-victoriametrics-makes-instant-snapshots-for-multi-terabyte-time-series-data-e1f3fb0e0282)
+to keep high performance during ingestion. These compactions (merges) are performed independently on per-month partitions.
+Partitions that don't receive new data will eventually stop merging parts, as they reach an optimal state.
+Sometimes it is necessary to trigger merges for old partitions. For example, to free up disk space occupied by [deleted time series](https://docs.victoriametrics.com/victoriametrics/#how-to-delete-time-series).
+User can **force** compaction on the specified per-month partition by sending request to `/internal/force_merge?partition_prefix=YYYY_MM`,
 where `YYYY_MM` is per-month partition name. For example, `http://victoriametrics:8428/internal/force_merge?partition_prefix=2020_08` would initiate forced
 merge for August 2020 partition. The call to `/internal/force_merge` returns immediately, while the corresponding forced merge continues running in background.
 
@@ -713,6 +713,26 @@ Forced merges may require additional CPU, disk IO and storage space resources. I
 since VictoriaMetrics automatically performs [optimal merges in background](https://medium.com/@valyala/how-victoriametrics-makes-instant-snapshots-for-multi-terabyte-time-series-data-e1f3fb0e0282)
 when new data is ingested into it.
 
+The `/internal/force_merge` endpoint can be protected from unauthorized access via `--forceMergeAuthKey` command-line flag.
+See [General security recommendations](https://docs.victoriametrics.com/victoriametrics/#general-security-recommendations) for more details.
+
+## Forced flush
+
+VictoriaMetrics puts the recently [ingested samples](https://docs.victoriametrics.com/victoriametrics/keyconcepts/#write-data) into in-memory buffers,
+which aren't available for [querying](https://docs.victoriametrics.com/victoriametrics/keyconcepts/#query-data) for up to a few seconds.
+If you need querying samples immediately after their ingestion, then call `/internal/force_flush` HTTP endpoint before querying.
+This endpoint converts in-memory buffers with the recently ingested samples into searchable data blocks.
+
+It isn't recommended requesting the `/internal/force_flush` HTTP endpoint on a regular basis, since this increases CPU usage
+and slows down data ingestion. It is expected that the `/internal/force_flush` is requested in automated tests, which need querying
+the recently ingested data.
+
+> VictoriaMetrics may intentionally hide samples with timestamps close to the current time during querying.
+> This behavior is controlled via `-search.latencyOffset` command-line flag. See more details in [Query latency](https://docs.victoriametrics.com/victoriametrics/keyconcepts/#query-latency) documentation.
+
+The `/internal/force_flush` endpoint can be protected from unauthorized access via `-forceFlushAuthKey` command-line flag.
+See [General security recommendations](https://docs.victoriametrics.com/victoriametrics/#general-security-recommendations) for more details.
+
 ## How to export time series
 
 VictoriaMetrics provides the following handlers for exporting data:
@@ -1738,8 +1758,8 @@ VictoriaMetrics provides the following security-related command-line flags:
   with [HTTP Basic Authentication](https://en.wikipedia.org/wiki/Basic_access_authentication).
 * `-deleteAuthKey` for protecting `/api/v1/admin/tsdb/delete_series` endpoint. See [how to delete time series](#how-to-delete-time-series).
 * `-snapshotAuthKey` for protecting `/snapshot*` endpoints. See [how to work with snapshots](#how-to-work-with-snapshots).
-* `-forceFlushAuthKey` for protecting `/internal/force_flush` endpoint. See [these docs](#troubleshooting).
-* `-forceMergeAuthKey` for protecting `/internal/force_merge` endpoint. See [force merge docs](#forced-merge).
+* `-forceFlushAuthKey` for protecting `/internal/force_flush` endpoint. See [force flush docs](https://docs.victoriametrics.com/victoriametrics/single-server-victoriametrics/#forced-flush).
+* `-forceMergeAuthKey` for protecting `/internal/force_merge` endpoint. See [force merge docs](https://docs.victoriametrics.com/victoriametrics/single-server-victoriametrics/#forced-merge).
 * `-search.resetCacheAuthKey` for protecting `/internal/resetRollupResultCache` endpoint. See [backfilling](#backfilling) for more details.
 * `-reloadAuthKey` for protecting `/-/reload` endpoint, which is used for force reloading of [`-promscrape.config`](#how-to-scrape-prometheus-exporters-such-as-node-exporter).
 * `-configAuthKey` for protecting `/config` endpoint, since it may contain sensitive information such as passwords.