app/vmagent/remotewrite: cosmetic updates after f3a51e8b1d

- Compare directory names instead of paths to directory when determining which persistent queues must be deleted
  This is less error-prone solution, since paths to the same directory can differ, which could lead
  to accidental directory removal for the existing -remoteWrite.url

- Log the `removed %d dangling queues` message when at least a single queue has been removed

- Consistently use filepath.Join() for creating paths to persistent queues.
  This is needed for Windows support (see https://github.com/VictoriaMetrics/VictoriaMetrics/issues/70 )

- Clarify the description of the change at docs/CHANGELOG.md

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4014

app/vmagent/remotewrite/remotewrite.go

@@ -100,7 +100,7 @@ var allRelabelConfigs atomic.Value
 // since it may lead to high memory usage due to big number of buffers.
 var maxQueues = cgroup.AvailableCPUs() * 16
 
-const persistentQueueDir = "persistent-queue"
+const persistentQueueDirname = "persistent-queue"
 
 // InitSecretFlags must be called after flag.Parse and before any logging.
 func InitSecretFlags() {
@@ -240,26 +240,28 @@ func newRemoteWriteCtxs(at *auth.Token, urls []string) []*remoteWriteCtx {
 		// See: https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4014
 		existingQueues := make(map[string]struct{}, len(rwctxs))
 		for _, rwctx := range rwctxs {
-			existingQueues[rwctx.fq.Dir()] = struct{}{}
+			existingQueues[rwctx.fq.Dirname()] = struct{}{}
 		}
 
-		queuesDir := filepath.Join(*tmpDataPath, persistentQueueDir)
+		queuesDir := filepath.Join(*tmpDataPath, persistentQueueDirname)
 		files, err := os.ReadDir(queuesDir)
 		if err != nil {
 			logger.Fatalf("cannot read queues dir %q: %s", queuesDir, err)
 		}
 		removed := 0
 		for _, f := range files {
-			fullPath := filepath.Join(queuesDir, f.Name())
-			if _, ok := existingQueues[fullPath]; !ok {
-				logger.Infof("removing dangling queue %q", fullPath)
+			dirname := f.Name()
+			if _, ok := existingQueues[dirname]; !ok {
+				logger.Infof("removing dangling queue %q", dirname)
+				fullPath := filepath.Join(queuesDir, dirname)
 				fs.MustRemoveAll(fullPath)
 				removed++
 			}
 		}
-
+		if removed > 0 {
 			logger.Infof("removed %d dangling queues from %q, active queues: %d", removed, *tmpDataPath, len(rwctxs))
 		}
+	}
 
 	return rwctxs
 }
@@ -502,7 +504,7 @@ func newRemoteWriteCtx(argIdx int, at *auth.Token, remoteWriteURL *url.URL, maxI
 	pqURL.RawQuery = ""
 	pqURL.Fragment = ""
 	h := xxhash.Sum64([]byte(pqURL.String()))
-	queuePath := fmt.Sprintf("%s/%s/%d_%016X", *tmpDataPath, persistentQueueDir, argIdx+1, h)
+	queuePath := filepath.Join(*tmpDataPath, persistentQueueDirname, fmt.Sprintf("%d_%016X", argIdx+1, h))
 	maxPendingBytes := maxPendingBytesPerURL.GetOptionalArgOrDefault(argIdx, 0)
 	fq := persistentqueue.MustOpenFastQueue(queuePath, sanitizedURL, maxInmemoryBlocks, maxPendingBytes)
 	_ = metrics.GetOrCreateGauge(fmt.Sprintf(`vmagent_remotewrite_pending_data_bytes{path=%q, url=%q}`, queuePath, sanitizedURL), func() float64 {

docs/CHANGELOG.md

@@ -25,6 +25,7 @@ created by v1.90.0 or newer versions. The solution is to upgrade to v1.90.0 or n
 * FEATURE: [vmagent](https://docs.victoriametrics.com/vmagent.html): add support for [VictoriaMetrics remote write protocol](https://docs.victoriametrics.com/vmagent.html#victoriametrics-remote-write-protocol) when [sending / receiving data to / from Kafka](https://docs.victoriametrics.com/vmagent.html#kafka-integration). This protocol allows saving egress network bandwidth costs when sending data from `vmagent` to `Kafka` located in another datacenter or availability zone. See [this feature request](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1225).
 * FEATURE: [vmagent](https://docs.victoriametrics.com/vmagent.html): add `-kafka.consumer.topic.concurrency` command-line flag. It controls the number of Kafka consumer workers to use by `vmagent`. It should eliminate the need to start multiple `vmagent` instances to improve data transfer rate. See [this feature request](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1957).
 * FEATURE: [vmagent](https://docs.victoriametrics.com/vmagent.html): add support for [Kafka producer and consumer](https://docs.victoriametrics.com/vmagent.html#kafka-integration) on `arm64` machines. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2271).
+* FEATURE: [vmagent](https://docs.victoriametrics.com/vmagent.html): delete unused buffered data at `-remoteWrite.tmpDataPath` directory when there is no matching `-remoteWrite.url` to send this data to. See [this feature request](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4014).
 * FEATURE: [vmui](https://docs.victoriametrics.com/#vmui): automatically draw a heatmap graph when the query selects a single [histogram](https://docs.victoriametrics.com/keyConcepts.html#histogram). This simplifies analyzing histograms. See [this feature request](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3384).
 * FEATURE: [vmui](https://docs.victoriametrics.com/#vmui): add support for drag'n'drop and paste from clipboard in the "Trace analyzer" page. See [this pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/3971).
 * FEATURE: [vmui](https://docs.victoriametrics.com/#vmui): hide messages longer than 3 lines in the trace. You can view the full message by clicking on the `show more` button. See [this pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/3971).
@@ -32,7 +33,6 @@ created by v1.90.0 or newer versions. The solution is to upgrade to v1.90.0 or n
 * FEATURE: [vmui](https://docs.victoriametrics.com/#vmui): updated usability and the search process in cardinality explorer. Made this process straightforward for user. See [this pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/3986).
 * FEATURE: [vmctl](https://docs.victoriametrics.com/vmctl.html): automatically disable progress bar when TTY isn't available. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3823).
 * FEATURE: [vmauth](https://docs.victoriametrics.com/vmauth.html): add `-configCheckInterval` command-line flag, which can be used for automatic re-reading the `-auth.config` file. See [this feature request](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3990).
-* FEATURE: [vmagent](https://docs.victoriametrics.com/vmagent.html): add `-remoteWrite.keepDanglingQueues` command-line flag. It allows to force `vmagent` to keep dangling queues on the disk when `vmagent` is started. By default, persistent queues without matching `remoteWrite.url` will be deleted. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4014).
 
 * BUGFIX: prevent from slow [snapshot creating](https://docs.victoriametrics.com/#how-to-work-with-snapshots) under high data ingestion rate. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3551).
 * BUGFIX: [vmauth](https://docs.victoriametrics.com/vmauth.html):  suppress [proxy protocol](https://www.haproxy.org/download/2.3/doc/proxy-protocol.txt) parsing errors in case of `EOF`. Usually, the error is caused by health checks and is not a sign of an actual error.

lib/persistentqueue/fastqueue.go

@@ -2,6 +2,7 @@ package persistentqueue
 
 import (
 	"fmt"
+	"path/filepath"
 	"sync"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
@@ -201,6 +202,6 @@ func (fq *FastQueue) MustReadBlock(dst []byte) ([]byte, bool) {
 }
 
 // Dir returns the directory for persistent queue.
-func (fq *FastQueue) Dir() string {
-	return fq.pq.dir
+func (fq *FastQueue) Dirname() string {
+	return filepath.Base(fq.pq.dir)
 }