lib/prommetadata: enable metrics metadata ingestion and storing by default (#10489)

### Describe Your Changes

Related to
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2974

### Checklist

The following checks are **mandatory**:

- [ ] My change adheres to [VictoriaMetrics contributing
guidelines](https://docs.victoriametrics.com/victoriametrics/contributing/#pull-request-checklist).
- [ ] My change adheres to [VictoriaMetrics development
goals](https://docs.victoriametrics.com/victoriametrics/goals/).

apptest/tests/metricsmetadata_test.go

@@ -19,7 +19,6 @@ func TestSingleMetricsMetadata(t *testing.T) {
 	sut := tc.MustStartVmsingle("vmsingle", []string{
 		"-storageDataPath=" + tc.Dir(),
 		"-retentionPeriod=100y",
-		"-enableMetadata",
 	})
 	// verify empty stats
 	resp := sut.PrometheusAPIV1Metadata(t, "", 0, apptest.QueryOpts{})
@@ -120,15 +119,12 @@ func TestClusterMetricsMetadata(t *testing.T) {
 
 	vminsert1 := tc.MustStartVminsert("vminsert1", []string{
 		fmt.Sprintf("-storageNode=%s,%s", vmstorage1.VminsertAddr(), vmstorage2.VminsertAddr()),
-		"-enableMetadata",
 	})
 	vminsert2 := tc.MustStartVminsert("vminsert-2", []string{
 		fmt.Sprintf("-storageNode=%s,%s", vmstorage1.VminsertAddr(), vmstorage2.VminsertAddr()),
-		"-enableMetadata",
 	})
 	vminsertGlobal := tc.MustStartVminsert("vminsert-global", []string{
 		fmt.Sprintf("-storageNode=%s,%s", vminsert1.ClusternativeListenAddr(), vminsert2.ClusternativeListenAddr()),
-		"-enableMetadata",
 	})
 	vmselect := tc.MustStartVmselect("vmselect", []string{
 		fmt.Sprintf("-storageNode=%s,%s", vmstorage1.VmselectAddr(), vmstorage2.VmselectAddr()),

docs/victoriametrics/Cluster-VictoriaMetrics.md

@@ -1015,7 +1015,7 @@ to ensure query results consistency, even if storage layer didn't complete dedup
 ## Metrics Metadata
 
 Cluster version of VictoriaMetrics can store metric metadata (TYPE, HELP, UNIT) {{% available_from "v1.130.0" %}}.
-Metadata ingestion is disabled by default. To enable it, set `-enableMetadata=true` on `vminsert` and `vmagent`.
+Metadata ingestion is enabled by default{{% available_from "#" %}}. To disable it, set `-enableMetadata=false` on `vminsert`, `vmstorage` and `vmagent`.
 
 The metadata is cached in-memory in a ring buffer and can use up to 1% of available memory by default (see `-storage.maxMetadataStorageSize` cmd-line flag).
 When in-memory size is exceeded, the least updated entries are dropped first. Entries that weren't updated for 1h are cleaned up automatically.

docs/victoriametrics/README.md

@@ -1371,7 +1371,7 @@ see [these docs](https://docs.victoriametrics.com/victoriametrics/stream-aggrega
 ## Metrics Metadata
 
 Single-node VictoriaMetrics can store metric metadata (`TYPE`, `HELP`, `UNIT`) {{% available_from "v1.130.0" %}}.
-Metadata ingestion and querying are disabled by default. To enable them, set `-enableMetadata=true`.
+Metadata ingestion and querying are enabled by default{{% available_from "#" %}}. To disable them, set `-enableMetadata=false`.
 
 The metadata is cached in-memory in a ring buffer and can use up to 1% of available memory by default (see `-storage.maxMetadataStorageSize` cmd-line flag).
 When in-memory size is exceeded, the least updated entries are dropped first. Entries that weren't updated for 1h are cleaned up automatically.

docs/victoriametrics/changelog/CHANGELOG.md

@@ -30,6 +30,7 @@ See also [LTS releases](https://docs.victoriametrics.com/victoriametrics/lts-rel
 * FEATURE: [vmauth](https://docs.victoriametrics.com/victoriametrics/vmauth/): add JWT token authentication support with signature verification based on provided `public_keys`. Read more about configuration in [JWT Token auth proxy](https://docs.victoriametrics.com/victoriametrics/vmauth/#jwt-token-auth-proxy) documentation. See [#10445](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/10445).
 * FEATURE: all VictoriaMetrics components: expose `process_cpu_seconds_total`, `process_resident_memory_bytes`, and other process-level metrics when running on macOS. See [metrics#75](https://github.com/VictoriaMetrics/metrics/issues/75).
 * FEATURE: [dashboards/vmauth](https://grafana.com/grafana/dashboards/21394): add `Request body buffering duration` panel to the `Troubleshooting` section. This panel shows the time spent buffering incoming client request bodies, helping identify slow client uploads and potential concurrency issues. The panel is only available when `-requestBufferSize` is non-zero. See [#10309](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/10309).
+* FEATURE: [vmagent](https://docs.victoriametrics.com/victoriametrics/vmagent/), [vmsingle](https://docs.victoriametrics.com/victoriametrics/single-server-victoriametrics/), `vminsert` and `vmstorage` in [VictoriaMetrics cluster](https://docs.victoriametrics.com/victoriametrics/cluster-victoriametrics/): enable [ingestion](https://docs.victoriametrics.com/victoriametrics/vmagent/#metric-metadata) and in-memory [storage](https://docs.victoriametrics.com/victoriametrics/single-server-victoriametrics/#metrics-metadata) of metrics metadata by default. Metadata ingestion can be disabled with `-enableMetadata=false`. See [#2974](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2974).
 
 ## [v1.136.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.136.0)
 

docs/victoriametrics/vmagent.md

@@ -658,12 +658,12 @@ e.g. it sets `scrape_series_added` metric to zero. See [these docs](#automatical
 
 ## Metric metadata
 
-By default, `vmagent` ignores metric metadata exposed by scrape targets in [Prometheus exposition format](https://github.com/prometheus/docs/blob/main/docs/instrumenting/exposition_formats.md), received via [Prometheus remote write v1](https://prometheus.io/docs/specs/prw/remote_write_spec/) or [OpenTelemetry protocol](https://github.com/open-telemetry/opentelemetry-proto/blob/v1.7.0/opentelemetry/proto/metrics/v1/metrics.proto). Set `-enableMetadata=true` to enable metadata processing{{% available_from "v1.125.1" %}}.
+`vmagent` accepts{{% available_from "#" %}} metric metadata exposed by scrape targets in [Prometheus exposition format](https://github.com/prometheus/docs/blob/main/docs/instrumenting/exposition_formats.md), received via [Prometheus remote write v1](https://prometheus.io/docs/specs/prw/remote_write_spec/) or [OpenTelemetry protocol](https://github.com/open-telemetry/opentelemetry-proto/blob/v1.7.0/opentelemetry/proto/metrics/v1/metrics.proto) by default. Set `-enableMetadata=false` to disable metadata processing{{% available_from "v1.125.1" %}}.
 During processing, metadata won't be dropped or modified by [relabeling](https://docs.victoriametrics.com/victoriametrics/relabeling/) or [streaming aggregation](https://docs.victoriametrics.com/victoriametrics/stream-aggregation/).
 
 When `-enableMultitenantHandlers` is enabled, vmagent adds tenant info to metadata received via the [multitenant endpoints](https://docs.victoriametrics.com/victoriametrics/vmagent/#multitenancy) (`/insert/<accountID>/<suffix>`). However, if `vm_account_id` or `vm_project_id` labels are added directly to metrics before reaching vmagent, and vmagent writes to the [vminsert multitenant endpoints](https://docs.victoriametrics.com/victoriametrics/cluster-victoriametrics/#multitenancy-via-labels), the tenant info won't be attached and the metadata will be stored under the default tenant of VictoriaMetrics cluster.
 
->Enabling metadata requires extra memory, disk space, and network traffic.
+> Metadata requires extra memory, disk space, and network traffic.
 
 ## Stream parsing mode
 

lib/prommetadata/metadata.go

@@ -2,7 +2,7 @@ package prommetadata
 
 import "flag"
 
-var enableMetadata = flag.Bool("enableMetadata", false, "Whether to enable metadata processing for metrics scraped from targets, received via VictoriaMetrics remote write, Prometheus remote write v1 or OpenTelemetry protocol. "+
+var enableMetadata = flag.Bool("enableMetadata", true, "Whether to enable metadata processing for metrics scraped from targets, received via VictoriaMetrics remote write, Prometheus remote write v1 or OpenTelemetry protocol. "+
 	"See also remoteWrite.maxMetadataPerBlock")
 
 // IsEnabled reports whether metadata processing is enabled.