[prometheusremotewriteexporter] Handle case with 0 metrics (#12489)

Fixes #10364

Signed-off-by: Goutham Veeramachaneni <[email protected]>

Signed-off-by: Goutham Veeramachaneni <[email protected]>
Co-authored-by: Bogdan Drutu <[email protected]>

exporter/prometheusremotewriteexporter/exporter.go

@@ -155,6 +155,11 @@ func validateAndSanitizeExternalLabels(cfg *Config) (map[string]string, error) {
 }
 
 func (prwe *prwExporter) handleExport(ctx context.Context, tsMap map[string]*prompb.TimeSeries) error {
+	// There are no metrics to export, so return.
+	if len(tsMap) == 0 {
+		return nil
+	}
+
 	// Calls the helper function to convert and batch the TsMap to the desired format
 	requests, err := batchTimeSeries(tsMap, maxBatchByteSize)
 	if err != nil {

exporter/prometheusremotewriteexporter/exporter_test.go

@@ -324,10 +324,22 @@ func Test_export(t *testing.T) {
 	}
 }
 
+func TestNoMetricsNoError(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusAccepted)
+	}))
+	defer server.Close()
+	serverURL, uErr := url.Parse(server.URL)
+	assert.NoError(t, uErr)
+	assert.NoError(t, runExportPipeline(nil, serverURL))
+}
+
 func runExportPipeline(ts *prompb.TimeSeries, endpoint *url.URL) error {
 	// First we will construct a TimeSeries array from the testutils package
 	testmap := make(map[string]*prompb.TimeSeries)
-	testmap["test"] = ts
+	if ts != nil {
+		testmap["test"] = ts
+	}
 
 	cfg := createDefaultConfig().(*Config)
 	cfg.HTTPClientSettings.Endpoint = endpoint.String()

unreleased/fix-0-len-prw-exports.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: prometheusremotewriteexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Handle the case with 0 metrics gracefully.
+
+# One or more tracking issues related to the change
+issues: [10364]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: