fix(loki.source.file): Keep positions for compressed files when reading is finished [backport]

internal/component/loki/source/file/tailer.go

@@ -265,9 +265,7 @@ func (t *tailer) stop(done chan struct{}) {
 	// We need to cleanup created metrics
 	t.cleanupMetrics()
 
-	// If the component is not stopping, then it means that the target for this component is gone and that
-	// we should clear the entry from the positions file.
-	if !t.componentStopping() {
+	if !t.shouldKeepPosition() {
 		t.positions.Remove(t.key.Path, t.key.Labels)
 	}
 }
@@ -276,6 +274,14 @@ func (t *tailer) Key() positions.Entry {
 	return t.key
 }
 
+func (t *tailer) shouldKeepPosition() bool {
+	// NOTE: We want to keep position if component is stopping or decompression is enabled.
+	// If component is not stopping that means that target is gone and we should no longer tail the file.
+	// If decompression is enabled we read file until we reach EOF and stop so tailer will exit, but we need
+	// to remember the position so that we don't re-ingest it on restart.
+	return t.componentStopping() || t.decompression.Enabled
+}
+
 // cleanupMetrics removes all metrics exported by this tailer
 func (t *tailer) cleanupMetrics() {
 	// When we stop tailing the file, also un-export metrics related to the file

internal/component/loki/source/file/tailer_test.go

@@ -361,7 +361,8 @@ func TestTailer_Compressions(t *testing.T) {
 		logger,
 		handler.Receiver(),
 		positionsFile,
-		func() bool { return true },
+		// We return false here to verify that position is kept and we don't re-ingest the file.
+		func() bool { return false },
 		sourceOptions{
 			path:                 filename,
 			labels:               labels,