app/vmagent: remove data race when applying rate limits to -remoteWrite.url with multiple queues

app/vmagent/remotewrite/client.go

@@ -299,6 +299,9 @@ again:
 type rateLimiter struct {
 	perSecondLimit int64
 
+	// mu protects budget and deadline from concurrent access.
+	mu sync.Mutex
+
 	// The current budget. It is increased by perSecondLimit every second.
 	budget int64
 
@@ -313,6 +316,10 @@ func (rl *rateLimiter) register(dataLen int, stopCh <-chan struct{}) {
 	if limit <= 0 {
 		return
 	}
+
+	rl.mu.Lock()
+	defer rl.mu.Unlock()
+
 	for rl.budget <= 0 {
 		now := time.Now()
 		if d := rl.deadline.Sub(now); d > 0 {

docs/CHANGELOG.md

@@ -20,6 +20,7 @@
 * FEATURE: vmagent: initial support for Windows build with `CGO_ENABLED=0 GOOS=windows go build -mod=vendor ./app/vmagent`. See [this](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/70) and [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1036).
 * FEATURE: vmalert: properly process query params in `-datasource.url` and `-remoteRead.url` command-line flags. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1087) for details.
 
+* BUGFIX: vmagent: properly apply `-remoteWrite.rateLimit` when `-remoteWrite.queues` is greater than 1. Previously there was a data race, which could prevent from proper rate limiting.
 * BUGFIX: vmagent: properly perform graceful shutdown on `SIGINT` and `SIGTERM` signals. The graceful shutdown has been broken in `v1.54.0`. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1065
 * BUGFIX: reduce the probability of `duplicate time series` errors when querying Kubernetes metrics.
 * BUGFIX: properly calculate `histogram_quantile()` over time series with only a single non-zero bucket with `{le="+Inf"}`. Previously `NaN` was returned, now the value for the last bucket before `{le="+Inf"}` is returned like Prometheus does.