docs/Cluster-VictoriaMetrics.md: document -disableReroutingOnUnavailable command-line flag

This is a follow-up for 88f0d1572e
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/5713

docs/CHANGELOG.md

@@ -36,6 +36,7 @@ Released at 2024-02-01
 All these fixes are also included in [the latest community release](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/latest).
 The v1.97.x line will be supported for at least 12 months since [v1.97.0](https://docs.victoriametrics.com/CHANGELOG.html#v1970) release**
 
+* FEATURE: [VictoriaMetrics cluster](https://docs.victoriametrics.com/Cluster-VictoriaMetrics.html): add `-disableReroutingOnUnavailable` command-line flag, which can be used for reducing resource usage spikes at `vmstorage` nodes during rolling restart. Thanks to @Muxa1L for [the pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/5713).
 * FEATURE: [vmagent](https://docs.victoriametrics.com/vmagent.html): add support for `username_file` option at `basic_auth` section in [`scrape_configs`](https://docs.victoriametrics.com/sd_configs/#http-api-client-options). See [this feature request](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5511). Thanks to @wasim-nihal for [the initial implementation](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/5720).
 * FEATURE: [dashboards/vmagent](https://grafana.com/grafana/dashboards/12683): add `Targets scraped/s` stat panel showing the number of targets scraped by the vmagent per-second.
 * FEATURE: [dashboards/all](https://grafana.com/orgs/victoriametrics): add new panel `CPU spent on GC`. It should help identifying cases when too much CPU is spent on garbage collection, and advice users on how this can be addressed.

docs/Cluster-VictoriaMetrics.md

@@ -509,14 +509,18 @@ The `minimum downtime` strategy has the following benefits comparing to `no down
 `vmstorage` nodes may experience increased usage for CPU, RAM and disk IO during
 [rolling restarts](https://docs.victoriametrics.com/Cluster-VictoriaMetrics.html#no-downtime-strategy),
 since they need to process higher load when some of `vmstorage` nodes are temporarily unavailable in the cluster.
-It is possible to reduce resource usage spikes by running more `vminsert` nodes and by passing bigger values
-to `-storage.vminsertConnsShutdownDuration` (available from [v1.95.0](https://docs.victoriametrics.com/CHANGELOG.html#v1950))
-command-line flag at `vmstorage` nodes.
-In this case `vmstorage` increases the interval between gradual closing of `vminsert` connections during graceful shutdown.
-This reduces data ingestion slowdown during rollout restarts.
 
-Make sure that the `-storage.vminsertConnsShutdownDuration` is smaller than the graceful shutdown timeout configured at the system which manages `vmstorage`
-(e.g. Docker, Kubernetes, systemd, etc.). Otherwise the system may kill `vmstorage` node before it finishes gradual closing of `vminsert` connections.
+The following approaches can be used for reducing resource usage at `vmstorage` nodes during rolling restart:
+
+- To pass `-disableReroutingOnUnavailable` command-line flag to `vminsert` nodes, so they pause data ingestion when `vmstorage` nodes are restarted
+  instead of re-routing the ingested data to other available `vmstorage` nodes.
+
+- To pass bigger values to `-storage.vminsertConnsShutdownDuration` (available from [v1.95.0](https://docs.victoriametrics.com/CHANGELOG.html#v1950))
+  command-line flag at `vmstorage` nodes.In this case `vmstorage` increases the interval between gradual closing of `vminsert` connections during graceful shutdown.
+  This reduces data ingestion slowdown during rollout restarts.
+
+  Make sure that the `-storage.vminsertConnsShutdownDuration` is smaller than the graceful shutdown timeout configured at the system which manages `vmstorage`
+  (e.g. Docker, Kubernetes, systemd, etc.). Otherwise the system may kill `vmstorage` node before it finishes gradual closing of `vminsert` connections.
 
 See also [minimum downtime strategy](#minimum-downtime-strategy).
 
@@ -970,7 +974,9 @@ Below is the output for `/path/to/vminsert -help`:
   -denyQueryTracing
      Whether to disable the ability to trace queries. See https://docs.victoriametrics.com/#query-tracing
   -disableRerouting
-     Whether to disable re-routing when some of vmstorage nodes accept incoming data at slower speed compared to other storage nodes. Disabled re-routing limits the ingestion rate by the slowest vmstorage node. On the other side, disabled re-routing minimizes the number of active time series in the cluster during rolling restarts and during spikes in series churn rate. See also -dropSamplesOnOverload (default true)
+     Whether to disable re-routing when some of vmstorage nodes accept incoming data at slower speed compared to other storage nodes. Disabled re-routing limits the ingestion rate by the slowest vmstorage node. On the other side, disabled re-routing minimizes the number of active time series in the cluster during rolling restarts and during spikes in series churn rate. See also -disableReroutingOnUnavailable and -dropSamplesOnOverload (default true)
+  -disableReroutingOnUnavailable
+     Whether to disable re-routing when some of vmstorage nodes are unavailable. Disabled re-routing stops ingestion when some storage nodes are unavailable. On the other side, disabled re-routing minimizes the number of active time series in the cluster during rolling restarts and during spikes in series churn rate. See also -disableRerouting
   -dropSamplesOnOverload
      Whether to drop incoming samples if the destination vmstorage node is overloaded and/or unavailable. This prioritizes cluster availability over consistency, e.g. the cluster continues accepting all the ingested samples, but some of them may be dropped if vmstorage nodes are temporarily unavailable and/or overloaded. The drop of samples happens before the replication, so it's not recommended to use this flag with -replicationFactor enabled.
   -enableTCP6