app/vmagent: add per-URL -remoteWrite.disableMetadata

Add per-URL `-remoteWrite.disableMetadata` flag to control metadata
sending for each remote storage independently.

After v1.137.0 enabled `-enableMetadata` by default, metadata is sent to
ALL remote write targets, even those with relabeling filters that drop
most metrics. This causes unnecessary growth in
`vmagent_remotewrite_requests_total`. and significant increase in
network load for heavy filtered remote write destinations.

app/vmagent/remotewrite/remotewrite.go

@@ -23,6 +23,7 @@ import (
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/memory"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/persistentqueue"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/procutil"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/prommetadata"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/prompb"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promrelabel"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promutil"
@@ -92,6 +93,8 @@ var (
 		"See https://docs.victoriametrics.com/victoriametrics/vmagent/#disabling-on-disk-persistence . See also -remoteWrite.dropSamplesOnOverload")
 	dropSamplesOnOverload = flag.Bool("remoteWrite.dropSamplesOnOverload", false, "Whether to drop samples when -remoteWrite.disableOnDiskQueue is set and if the samples "+
 		"cannot be pushed into the configured -remoteWrite.url systems in a timely manner. See https://docs.victoriametrics.com/victoriametrics/vmagent/#disabling-on-disk-persistence")
+	disableMetadataPerURL = flagutil.NewArrayBool("remoteWrite.disableMetadata", "Whether to disable sending metadata to the corresponding -remoteWrite.url. "+
+		"By default, metadata sending is controlled by the global -enableMetadata flag")
 )
 
 var (
@@ -540,6 +543,10 @@ func tryPushMetadataToRemoteStorages(rwctxs []*remoteWriteCtx, mms []prompb.Metr
 	var wg sync.WaitGroup
 	var anyPushFailed atomic.Bool
 	for _, rwctx := range rwctxs {
+		if !rwctx.enableMetadata {
+			// Skip remote storage with disabled metadata
+			continue
+		}
 		wg.Go(func() {
 			if !rwctx.tryPushMetadataInternal(mms) {
 				rwctx.pushFailures.Inc()
@@ -811,6 +818,11 @@ type remoteWriteCtx struct {
 	streamAggrKeepInput bool
 	streamAggrDropInput bool
 
+	// enableMetadata indicates whether metadata should be sent to this remote storage.
+	// It is determined by -remoteWrite.enableMetadata per-URL flag if set,
+	// otherwise by the global -enableMetadata flag.
+	enableMetadata bool
+
 	pss        []*pendingSeries
 	pssNextIdx atomic.Uint64
 
@@ -822,6 +834,18 @@ type remoteWriteCtx struct {
 	rowsDroppedOnPushFailure     *metrics.Counter
 }
 
+// isMetadataEnabledForURL returns true if metadata should be sent to the remote storage at argIdx.
+// It checks the per-URL -remoteWrite.disableMetadata flag first.
+// If not set, it falls back to the global -enableMetadata flag.
+func isMetadataEnabledForURL(argIdx int) bool {
+	if disableMetadataPerURL.GetOptionalArg(argIdx) {
+		// Metadata is explicitly disabled for this URL
+		return false
+	}
+	// Use global -enableMetadata value
+	return prommetadata.IsEnabled()
+}
+
 func newRemoteWriteCtx(argIdx int, remoteWriteURL *url.URL, sanitizedURL string) *remoteWriteCtx {
 	// strip query params, otherwise changing params resets pq
 	pqURL := *remoteWriteURL
@@ -892,10 +916,11 @@ func newRemoteWriteCtx(argIdx int, remoteWriteURL *url.URL, sanitizedURL string)
 	}
 
 	rwctx := &remoteWriteCtx{
-		idx: argIdx,
-		fq:  fq,
-		c:   c,
-		pss: pss,
+		idx:            argIdx,
+		fq:             fq,
+		c:              c,
+		pss:            pss,
+		enableMetadata: isMetadataEnabledForURL(argIdx),
 
 		rowsPushedAfterRelabel: metrics.GetOrCreateCounter(fmt.Sprintf(`vmagent_remotewrite_rows_pushed_after_relabel_total{path=%q,url=%q}`, queuePath, sanitizedURL)),
 		rowsDroppedByRelabel:   metrics.GetOrCreateCounter(fmt.Sprintf(`vmagent_remotewrite_relabel_metrics_dropped_total{path=%q,url=%q}`, queuePath, sanitizedURL)),

docs/victoriametrics/changelog/CHANGELOG.md

@@ -26,6 +26,7 @@ See also [LTS releases](https://docs.victoriametrics.com/victoriametrics/lts-rel
 
 ## tip
 
+* FEATURE: [vmagent](https://docs.victoriametrics.com/victoriametrics/vmagent/): add per-URL `-remoteWrite.disableMetadata` flag to disable metadata sending for specific remote storage URLs. See [#10711](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/10711). Thanks to @evkuzin for the contribution.
 * FEATURE: introduce `vm_filestream_fsync_duration_seconds_total` and `vm_filestream_fsync_calls_total` metrics, which can be used for detecting slow storage if it cannot keep up with the current data ingestion rate. See [#10432](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/10432). Thanks to @mehrdadbn9 for the contribution.
 * FEATURE: [vmctl](https://docs.victoriametrics.com/victoriametrics/vmctl/): add dedicated `thanos` mode for [migrating data from Thanos](https://docs.victoriametrics.com/victoriametrics/vmctl/thanos/). This mode supports both raw and downsampled Thanos blocks, including all aggregate types (count, sum, min, max, counter). Each aggregate is imported as a separate metric with resolution and aggregate type suffixes (e.g., `metric_name:5m:count`). The new mode uses `--thanos-*` prefixed flags: `--thanos-snapshot`, `--thanos-concurrency`, `--thanos-filter-time-start`, `--thanos-filter-time-end`, `--thanos-filter-label`, `--thanos-filter-label-value`, and `--thanos-aggr-types`. See [#9262](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/9262).