push.go: expose InitPushExtWithOptions() function, since this it is n…

…eede by VictoriaMetrics

push.go

@@ -52,7 +52,7 @@ func InitPushWithOptions(ctx context.Context, pushURL string, interval time.Dura
 	writeMetrics := func(w io.Writer) {
 		WritePrometheus(w, pushProcessMetrics)
 	}
-	return initPushWithOptions(ctx, pushURL, interval, writeMetrics, opts)
+	return InitPushExtWithOptions(ctx, pushURL, interval, writeMetrics, opts)
 }
 
 // InitPushProcessMetrics sets up periodic push for 'process_*' metrics to the given pushURL with the given interval.
@@ -115,7 +115,7 @@ func (s *Set) InitPushWithOptions(ctx context.Context, pushURL string, interval
 	writeMetrics := func(w io.Writer) {
 		s.WritePrometheus(w)
 	}
-	return initPushWithOptions(ctx, pushURL, interval, writeMetrics, opts)
+	return InitPushExtWithOptions(ctx, pushURL, interval, writeMetrics, opts)
 }
 
 // InitPush sets up periodic push for metrics from s to the given pushURL with the given interval.
@@ -158,10 +158,27 @@ func InitPushExt(pushURL string, interval time.Duration, extraLabels string, wri
 	opts := &PushOptions{
 		ExtraLabels: extraLabels,
 	}
-	return initPushWithOptions(context.Background(), pushURL, interval, writeMetrics, opts)
+	return InitPushExtWithOptions(context.Background(), pushURL, interval, writeMetrics, opts)
 }
 
-func initPushWithOptions(ctx context.Context, pushURL string, interval time.Duration, writeMetrics func(w io.Writer), opts *PushOptions) error {
+// InitPushExtWithOptions sets up periodic push for metrics obtained by calling writeMetrics with the given interval.
+//
+// The writeMetrics callback must write metrics to w in Prometheus text exposition format without timestamps and trailing comments.
+// See https://github.com/prometheus/docs/blob/main/content/docs/instrumenting/exposition_formats.md#text-based-format
+//
+// The periodic push is stopped when the ctx is canceled.
+//
+// opts may contain additional configuration options if non-nil.
+//
+// It is recommended pushing metrics to /api/v1/import/prometheus endpoint according to
+// https://docs.victoriametrics.com/#how-to-import-data-in-prometheus-exposition-format
+//
+// It is OK calling InitPushExtWithOptions multiple times with different pushURL -
+// in this case metrics are pushed to all the provided pushURL urls.
+//
+// It is OK calling InitPushExtWithOptions multiple times with different writeMetrics -
+// in this case all the metrics generated by writeMetrics callbacks are written to pushURL.
+func InitPushExtWithOptions(ctx context.Context, pushURL string, interval time.Duration, writeMetrics func(w io.Writer), opts *PushOptions) error {
 	// validate pushURL
 	pu, err := url.Parse(pushURL)
 	if err != nil {