fix(@opentelemetry/exporter-prometheus): unref prometheus server to p…

…revent process running indefinitely (#2558)
open-telemetry · Oct 26, 2021 · c1939a7 · c1939a7
1 parent b531acf
commit c1939a7
Show file tree

Hide file tree

Showing 2 changed files with 13 additions and 1 deletion.
diff --git a/experimental/packages/opentelemetry-exporter-prometheus/src/PrometheusExporter.ts b/experimental/packages/opentelemetry-exporter-prometheus/src/PrometheusExporter.ts
@@ -68,7 +68,8 @@ export class PrometheusExporter implements MetricExporter {
       typeof config.appendTimestamp === 'boolean'
         ? config.appendTimestamp
         : PrometheusExporter.DEFAULT_OPTIONS.appendTimestamp;
-    this._server = createServer(this._requestHandler);
+    // unref to prevent prometheus exporter from holding the process open on exit
+    this._server = createServer(this._requestHandler).unref();
     this._serializer = new PrometheusSerializer(
       this._prefix,
       this._appendTimestamp

diff --git a/experimental/packages/opentelemetry-exporter-prometheus/test/PrometheusExporter.test.ts b/experimental/packages/opentelemetry-exporter-prometheus/test/PrometheusExporter.test.ts
@@ -36,6 +36,7 @@ describe('PrometheusExporter', () => {
   mockAggregator(HistogramAggregator);
 
   afterEach(() => {
+    sinon.restore();
     delete process.env.OTEL_EXPORTER_PROMETHEUS_HOST;
     delete process.env.OTEL_EXPORTER_PROMETHEUS_PORT;
   });
@@ -116,6 +117,16 @@ describe('PrometheusExporter', () => {
       );
     });
 
+    it('should unref the server to allow graceful termination', () => {
+      const mockServer = sinon.createStubInstance(http.Server);
+      const createStub = sinon.stub(http, 'createServer');
+      createStub.returns((mockServer as any) as http.Server);
+      const exporter = new PrometheusExporter({}, async () => {
+        await exporter.shutdown();
+      });
+      sinon.assert.calledOnce(mockServer.unref);
+    });
+
     it('should listen on environmentally set host and port', () => {
       process.env.OTEL_EXPORTER_PROMETHEUS_HOST = '127.0.0.1';
       process.env.OTEL_EXPORTER_PROMETHEUS_PORT = '1234';