Address code review comments

Signed-off-by: Filip Petkovski <[email protected]>

cmd/thanos/receive.go

@@ -789,7 +789,7 @@ func (rc *receiveConfig) registerFlag(cmd extkingpin.FlagClause) {
 
 	rc.objStoreConfig = extkingpin.RegisterCommonObjStoreFlags(cmd, "", false)
 
-	rc.retention = extkingpin.ModelDuration(cmd.Flag("tsdb.retention", "How long to retain raw samples on local storage. 0d - disables this retention.").Default("15d"))
+	rc.retention = extkingpin.ModelDuration(cmd.Flag("tsdb.retention", "How long to retain raw samples on local storage. 0d - disables this retention. For more details on how retention is enforced for individual tenants, please refer to the Tenant lifecycle management section in the Receive documentation.").Default("15d"))
 
 	cmd.Flag("receive.hashrings-file", "Path to file that contains the hashring configuration. A watcher is initialized to watch changes and update the hashring dynamically.").PlaceHolder("<path>").StringVar(&rc.hashringsFilePath)
 

pkg/receive/multitsdb.go

@@ -202,6 +202,11 @@ func (t *MultiTSDB) Close() error {
 // Prune flushes and closes the TSDB for tenants that haven't received
 // any new samples for longer than the TSDB retention period.
 func (t *MultiTSDB) Prune(ctx context.Context) error {
+	// Retention of 0 means infinite retention.
+	if t.tsdbOpts.RetentionDuration == 0 {
+		return nil
+	}
+
 	t.mtx.Lock()
 	defer t.mtx.Unlock()