lib/storage: change default value for maxLabelValueLen to 1024 (#6313)

* It must reduce memory usage for misbehaving clients. Since
VictoriaMetrics stores sparse index inmemory.
* Reduce disk space usage for indexdb.
* Prevent possible indexDB items drops.
* It may trigger slow insert and new timeseries registration due to
default value for flag change

https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6176

---------

Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>

README.md

@@ -1172,7 +1172,7 @@ Below is the output for `/path/to/vminsert -help`:
      The maximum size in bytes of a single Prometheus remote_write API request
      Supports the following optional suffixes for size values: KB, MB, GB, TB, KiB, MiB, GiB, TiB (default 33554432)
   -maxLabelValueLen int
-     The maximum length of label values in the accepted time series. Longer label values are truncated. In this case the vm_too_long_label_values_total metric at /metrics page is incremented (default 16384)
+     The maximum length of label values in the accepted time series. Longer label values are truncated. In this case the vm_too_long_label_values_total metric at /metrics page is incremented (default 1024)
   -maxLabelsPerTimeseries int
      The maximum number of labels accepted per time series. Superfluous labels are dropped. In this case the vm_metrics_with_dropped_labels_total metric at /metrics page is incremented (default 30)
   -memory.allowedBytes size

app/vminsert/main.go

@@ -76,7 +76,7 @@ var (
 		"See https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt . "+
 		"With enabled proxy protocol http server cannot serve regular /metrics endpoint. Use -pushmetrics.url for metrics pushing")
 	maxLabelsPerTimeseries = flag.Int("maxLabelsPerTimeseries", 30, "The maximum number of labels accepted per time series. Superfluous labels are dropped. In this case the vm_metrics_with_dropped_labels_total metric at /metrics page is incremented")
-	maxLabelValueLen       = flag.Int("maxLabelValueLen", 16*1024, "The maximum length of label values in the accepted time series. Longer label values are truncated. In this case the vm_too_long_label_values_total metric at /metrics page is incremented")
+	maxLabelValueLen       = flag.Int("maxLabelValueLen", 1024, "The maximum length of label values in the accepted time series. Longer label values are truncated. In this case the vm_too_long_label_values_total metric at /metrics page is incremented")
 	storageNodes           = flagutil.NewArrayString("storageNode", "Comma-separated addresses of vmstorage nodes; usage: -storageNode=vmstorage-host1,...,vmstorage-hostN . "+
 		"Enterprise version of VictoriaMetrics supports automatic discovery of vmstorage addresses via DNS SRV records. For example, -storageNode=srv+vmstorage.addrs . "+
 		"See https://docs.victoriametrics.com/cluster-victoriametrics/#automatic-vmstorage-discovery")

docs/CHANGELOG.md

@@ -33,6 +33,7 @@ See also [LTS releases](https://docs.victoriametrics.com/lts-releases/).
 **Update note 1: the `-remoteWrite.multitenantURL` command-line flag at `vmagent` was removed starting from this release. This flag was deprecated since [v1.96.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.96.0). Use `-enableMultitenantHandlers` instead, as it is easier to use and combine with [multitenant URL at vminsert](https://docs.victoriametrics.com/Cluster-VictoriaMetrics.html#multitenancy-via-labels). See these [docs for details](https://docs.victoriametrics.com/vmagent.html#multitenancy).**
 
 **Update note 2: the `-streamAggr.dropInputLabels` command-line flag at `vmagent` was renamed to `-remoteWrite.streamAggr.dropInputLabels`. `-streamAggr.dropInputLabels` is now used for global streaming aggregation.**
+**Update note 3: the `-maxLabelValueLen` command-line flag default value was changed from 16kB to 1kB. It may lead to truncating of labels with enormous values.**
 
 * SECURITY: upgrade Go builder from Go1.22.2 to Go1.22.3. See [the list of issues addressed in Go1.22.3](https://github.com/golang/go/issues?q=milestone%3AGo1.22.3+label%3ACherryPickApproved).
 
@@ -62,6 +63,7 @@ See also [LTS releases](https://docs.victoriametrics.com/lts-releases/).
 * BUGFIX: [stream aggregation](https://docs.victoriametrics.com/stream-aggregation/): prevent from excessive resource usage when stream aggregation config file is empty. 
 * BUGFIX: properly estimate the needed memory for query execution if it has the format [`aggr_func`](https://docs.victoriametrics.com/metricsql/#aggregate-functions)([`rollup_func[d]`](https://docs.victoriametrics.com/metricsql/#rollup-functions) (for example, `sum(rate(request_duration_seconds_bucket[5m]))`). This should allow performing aggregations over bigger number of time series when VictoriaMetrics runs in environments with small amounts of available memory. The issue has been introduced in [this commit](https://github.com/VictoriaMetrics/VictoriaMetrics/commit/5138eaeea0791caa34bcfab410e0ca9cd253cd8f) in [v1.83.0](https://docs.victoriametrics.com/changelog_2022/#v1830).
 * BUGFIX: [Single-node VictoriaMetrics](https://docs.victoriametrics.com/) and `vmstorage` in [VictoriaMetrics cluster](https://docs.victoriametrics.com/cluster-victoriametrics/): correctly apply `-inmemoryDataFlushInterval` when it's set to minimum supported value 1s.
+* BUGFIX: [Single-node VictoriaMetrics](https://docs.victoriametrics.com/) and `vminsert` in [VictoriaMetrics cluster](https://docs.victoriametrics.com/cluster-victoriametrics/): reduce the default value for `-maxLabelValueLen` command-line flag from `16KiB` to `1KiB`. This should prevent from issues like [this one](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6176) when time series with too long labels are ingested into VictoriaMetrics.
 * BUGFIX: [vmauth](https://docs.victoriametrics.com/vmauth/): properly release memory used for metrics during config reload. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6247).
 * BUGFIX: [dashboards](https://grafana.com/orgs/victoriametrics): fix `AnnotationQueryRunner` error in Grafana when executing annotations query against Prometheus backend. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6309) for details.
 

docs/README.md

@@ -2915,7 +2915,7 @@ Pass `-help` to VictoriaMetrics in order to see the list of supported command-li
      The maximum size in bytes of a single Prometheus remote_write API request
      Supports the following optional suffixes for size values: KB, MB, GB, TB, KiB, MiB, GiB, TiB (default 33554432)
   -maxLabelValueLen int
-     The maximum length of label values in the accepted time series. Longer label values are truncated. In this case the vm_too_long_label_values_total metric at /metrics page is incremented (default 16384)
+     The maximum length of label values in the accepted time series. Longer label values are truncated. In this case the vm_too_long_label_values_total metric at /metrics page is incremented (default 1024)
   -maxLabelsPerTimeseries int
      The maximum number of labels accepted per time series. Superfluous labels are dropped. In this case the vm_metrics_with_dropped_labels_total metric at /metrics page is incremented (default 30)
   -memory.allowedBytes size

docs/Single-server-VictoriaMetrics.md

@@ -2923,7 +2923,7 @@ Pass `-help` to VictoriaMetrics in order to see the list of supported command-li
      The maximum size in bytes of a single Prometheus remote_write API request
      Supports the following optional suffixes for size values: KB, MB, GB, TB, KiB, MiB, GiB, TiB (default 33554432)
   -maxLabelValueLen int
-     The maximum length of label values in the accepted time series. Longer label values are truncated. In this case the vm_too_long_label_values_total metric at /metrics page is incremented (default 16384)
+     The maximum length of label values in the accepted time series. Longer label values are truncated. In this case the vm_too_long_label_values_total metric at /metrics page is incremented (default 1024)
   -maxLabelsPerTimeseries int
      The maximum number of labels accepted per time series. Superfluous labels are dropped. In this case the vm_metrics_with_dropped_labels_total metric at /metrics page is incremented (default 30)
   -memory.allowedBytes size

docs/keyConcepts.md

@@ -349,7 +349,7 @@ This limit can be changed via `-maxLabelsPerTimeseries` command-line flag if nec
 Every label value can contain an arbitrary string value. The good practice is to use short and meaningful label values to
 describe the attribute of the metric, not to tell the story about it. For example, label-value pair
 `environment="prod"` is ok, but `log_message="long log message with a lot of details..."` is not ok. By default,
-VictoriaMetrics limits label's value size with 16kB. This limit can be changed via `-maxLabelValueLen` command-line flag.
+VictoriaMetrics limits label's value size with 1kB. This limit can be changed via `-maxLabelValueLen` command-line flag.
 
 It is very important to keep under control the number of unique label values, since every unique label value
 leads to a new [time series](#time-series). Try to avoid using volatile label values such as session ID or query ID in order to

lib/storage/metric_name.go

@@ -542,7 +542,7 @@ const maxLabelNameLen = 256
 // The maximum length of label value.
 //
 // Longer values are truncated.
-var maxLabelValueLen = 16 * 1024
+var maxLabelValueLen = 1024
 
 // SetMaxLabelValueLen sets the limit on the label value length.
 //
@@ -659,8 +659,10 @@ func trackTruncatedLabels(labels []prompb.Label, truncated *prompb.Label, accoun
 	}
 }
 
-var droppedLabelsLogTicker = time.NewTicker(5 * time.Second)
-var truncatedLabelsLogTicker = time.NewTicker(5 * time.Second)
+var (
+	droppedLabelsLogTicker   = time.NewTicker(5 * time.Second)
+	truncatedLabelsLogTicker = time.NewTicker(5 * time.Second)
+)
 
 func labelsToString(labels []prompb.Label) string {
 	labelsCopy := append([]prompb.Label{}, labels...)
@@ -855,6 +857,7 @@ func (ts *canonicalTagsSort) Less(i, j int) bool {
 	x := *ts
 	return string(x[i].key) < string(x[j].key)
 }
+
 func (ts *canonicalTagsSort) Swap(i, j int) {
 	x := *ts
 	x[i], x[j] = x[j], x[i]