docs/stream-aggregation.md: clarify the usage of -remoteWrite.label after the fix at a27c2f3773

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4247

docs/CHANGELOG.md

@@ -27,7 +27,7 @@ The following `tip` changes can be tested by building VictoriaMetrics components
 * FEATURE: [vmbackup](https://docs.victoriametrics.com/vmbackup.html): add support for server-side copy of existing backups. See [these docs](https://docs.victoriametrics.com/vmbackup.html#server-side-copy-of-the-existing-backup) for details.
 
 * BUGFIX: do not allow starting VictoriaMetrics components with improperly set boolean command-line flags in the form `-boolFlagName value`, since this leads to silent incomplete flags' parsing. This form should be replaced with `-boolFlagName=value`. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4845).
-* BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): according to [the docs](https://docs.victoriametrics.com/vmagent.html#adding-labels-to-metrics) labels from `-remoteWrite.label` cmd-line flag are now added to the sent metrics just before they are pushed to the `-remoteWrite.url` (after all relabeling, including stream aggregation relabeling). In addition, it allows adding labels for identifying vmagent instances when using streaming aggregation in vmagents [cluster mode](https://docs.victoriametrics.com/vmagent.html#scraping-big-number-of-targets). See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4247) and [these docs](https://docs.victoriametrics.com/stream-aggregation.html#cluster-mode) for more details.
+* BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): properly set labels from `-remoteWrite.label` command-line flag just before sending samples to the configured `-remoteWrite.url` according to [these docs](https://docs.victoriametrics.com/vmagent.html#adding-labels-to-metrics). Previously these labels were incorrectly set before [the relabeling](https://docs.victoriametrics.com/vmagent.html#relabeling) configured via `-remoteWrite.urlRelabelConfigs` and [the stream aggregation](https://docs.victoriametrics.com/stream-aggregation.html) configured via `-remoteWrite.streamAggr.config`, so these labels could be lost or incorrectly transformed before sending the samples to remote storage. The fix allows using `-remoteWrite.label` for identifying `vmagent` instances in [cluster mode](https://docs.victoriametrics.com/vmagent.html#scraping-big-number-of-targets). See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4247) and [these docs](https://docs.victoriametrics.com/stream-aggregation.html#cluster-mode) for more details.
 * BUGFIX: remove `DEBUG` logging when parsing `if` filters inside [relabeling rules](https://docs.victoriametrics.com/vmagent.html#relabeling-enhancements) and when parsing `match` filters inside [stream aggregation rules](https://docs.victoriametrics.com/stream-aggregation.html).
 * BUGFIX: properly replace `:` chars in label names with `_` when `-usePromCompatibleNaming` command-line flag is passed to `vmagent`, `vminsert` or single-node VictoriaMetrics. This addresses [this comment](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3113#issuecomment-1275077071).
 * BUGFIX: [Official Grafana dashboards for VictoriaMetrics](https://grafana.com/orgs/victoriametrics): fix display of ingested rows rate for `Samples ingested/s` and `Samples rate` panels for vmagent's dasbhoard. Previously, not all ingested protocols were accounted in these panels. An extra panel `Rows rate` was added to `Ingestion` section to display the split for rows ingested rate by protocol.

docs/README.md

@@ -176,7 +176,8 @@ VictoriaMetrics is developed at a fast pace, so it is recommended periodically c
 
 ### Environment variables
 
-All the VictoriaMetrics components allow referring environment variables in command-line flags via `%{ENV_VAR}` syntax.
+All the VictoriaMetrics components allow referring environment variables in `yaml` configuration files (such as `-promscrape.config`)
+and in command-line flags via `%{ENV_VAR}` syntax.
 For example, `-metricsAuthKey=%{METRICS_AUTH_KEY}` is automatically expanded to `-metricsAuthKey=top-secret`
 if `METRICS_AUTH_KEY=top-secret` environment variable exists at VictoriaMetrics startup.
 This expansion is performed by VictoriaMetrics itself.

docs/Single-server-VictoriaMetrics.md

@@ -184,7 +184,8 @@ VictoriaMetrics is developed at a fast pace, so it is recommended periodically c
 
 ### Environment variables
 
-All the VictoriaMetrics components allow referring environment variables in command-line flags via `%{ENV_VAR}` syntax.
+All the VictoriaMetrics components allow referring environment variables in `yaml` configuration files (such as `-promscrape.config`)
+and in command-line flags via `%{ENV_VAR}` syntax.
 For example, `-metricsAuthKey=%{METRICS_AUTH_KEY}` is automatically expanded to `-metricsAuthKey=top-secret`
 if `METRICS_AUTH_KEY=top-secret` environment variable exists at VictoriaMetrics startup.
 This expansion is performed by VictoriaMetrics itself.

docs/stream-aggregation.md

@@ -678,8 +678,12 @@ support the following approaches for hot reloading stream aggregation configs fr
 
 If you use [vmagent in cluster mode](https://docs.victoriametrics.com/vmagent.html#scraping-big-number-of-targets) for streaming aggregation
 (with `-promscrape.cluster.*` parameters or with `VMAgent.spec.shardCount > 1` for [vmoperator](https://docs.victoriametrics.com/operator))
-then be careful when aggregating metrics via `by`, `without` or modifying via`*_relabel_configs` parameters, as incorrect usage may result in duplicates and data collision. For example, if more than one vmagent calculates `increase` for metric `http_requests_total` with `by: [path]` directive, then the resulting time series written to the remote database will be indistinguishable, as there is no way to tell to which `instance` the aggregation belongs. The proper fix would be to add a unique aggregation dimension: `by: [instance, path]`. With this change, aggregates between `instances` won't collide.
+then be careful when aggregating metrics via `by`, `without` or modifying via `*_relabel_configs` parameters, since incorrect usage
+may result in duplicates and data collision. For example, if more than one `vmagent` instance calculates `increase` for metric `http_requests_total`
+with `by: [path]` directive, then all the `vmagent` instances will aggregate samples to the same set of time series with different `path` labels.
+The proper fix would be to add an unique [`-remoteWrite.label`]https://docs.victoriametrics.com/vmagent.html#adding-labels-to-metrics() per each `vmagent`,
+so every `vmagent` aggregates data into distinct set of time series. These time series then can be aggregated later as needed during querying.
 
-If adding a new aggregation dimension isn't feasible (due to cardinality reduction purposes), then it is worth at least differentiating by which vmagent the aggregation was performed. You can do it with `remoteWrite.label` [parameter in vmagent](https://docs.victoriametrics.com/vmagent.html#adding-labels-to-metrics).
-For example, for running in docker or k8s you can use `remoteWrite.label` with `POD_NAME` or `HOSTNAME` environment variable: `remoteWrite.label='vmagent=%{HOSTNAME}'`.
-See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4247#issue-1692894073) for details.
+For example, if `vmagent` instances run in Docker or Kubernetes, then you can refer `POD_NAME` or `HOSTNAME` environment variables
+as an unique label value per each `vmagent`: `-remoteWrite.label='vmagent=%{HOSTNAME}` . See [these docs](https://docs.victoriametrics.com/#environment-variables)
+on how to refer environment variables in VictoriaMetrics components.