feat: added INSTANA_DISABLE_METRICS env

refs https://jsw.ibm.com/browse/INSTA-66149

Author: kirrg001

packages/collector/src/announceCycle/agentready.js

@@ -109,7 +109,11 @@ function enter(_ctx) {
 
   if (isMainThread) {
     uncaught.activate();
-    metrics.activate();
+
+    if (process.env.INSTANA_DISABLE_METRICS !== 'true') {
+      metrics.activate();
+    }
+
     requestHandler.activate();
     transmissionCycle.activate(
       metrics,

packages/collector/src/index.js

@@ -142,7 +142,12 @@ function init(userConfig = {}) {
 
   if (isMainThread) {
     uncaught.init(config, agentConnection, pidStore);
-    metrics.init(config, pidStore);
+
+    if (process.env.INSTANA_DISABLE_METRICS !== 'true') {
+      metrics.init(config, pidStore);
+    } else {
+      logger.info('Metrics collection is disabled via INSTANA_DISABLE_METRICS.');
+    }
   }
 
   logger.info(`@instana/collector module version: ${require(path.join(__dirname, '..', 'package.json')).version}`);

packages/collector/src/metrics/transmissionCycle.js

@@ -81,7 +81,10 @@ exports.activate = function activate(_metrics, _downstreamConnection, _onSuccess
   isActive = true;
 
   transmissionsSinceLastFullDataEmit = 0;
-  sendMetrics();
+
+  if (process.env.INSTANA_DISABLE_METRICS !== 'true') {
+    sendMetrics();
+  }
 };
 
 function sendMetrics() {

packages/collector/test/tracing/misc/metrics_deactivated/app.js

@@ -0,0 +1,46 @@
+/*
+ * (c) Copyright IBM Corp. 2025
+ */
+
+'use strict';
+
+// NOTE: c8 bug https://github.com/bcoe/c8/issues/166
+process.on('SIGTERM', () => {
+  process.disconnect();
+  process.exit(0);
+});
+
+require('../../../..')();
+const express = require('express');
+const morgan = require('morgan');
+const bodyParser = require('body-parser');
+const port = require('../../../test_util/app-port')();
+const app = express();
+const logPrefix = `Metrics activation is off (${process.pid}):\t`;
+const agentPort = process.env.INSTANA_AGENT_PORT;
+
+if (process.env.WITH_STDOUT) {
+  app.use(morgan(`${logPrefix}:method :url :status`));
+}
+
+app.use(bodyParser.json());
+
+app.get('/', (req, res) => {
+  res.sendStatus(200);
+});
+
+app.post('/create-spans', async (req, res) => {
+  await fetch(`http://localhost:${agentPort}/ping`);
+  res.json({ message: 'OK' });
+});
+
+app.listen(port, () => {
+  log(`Listening on port: ${port}`);
+});
+
+function log() {
+  /* eslint-disable no-console */
+  const args = Array.prototype.slice.call(arguments);
+  args[0] = logPrefix + args[0];
+  console.log.apply(console, args);
+}

packages/collector/test/tracing/misc/metrics_deactivated/test.js

@@ -0,0 +1,60 @@
+/*
+ * (c) Copyright IBM Corp. 2025
+ */
+
+'use strict';
+
+const expect = require('chai').expect;
+const supportedVersion = require('@instana/core').tracing.supportedVersion;
+
+const config = require('../../../../../core/test/config');
+const testUtils = require('../../../../../core/test/test_util');
+const ProcessControls = require('../../../test_util/ProcessControls');
+const globalAgent = require('../../../globalAgent');
+
+const mochaSuiteFn = supportedVersion(process.versions.node) ? describe : describe.skip;
+
+mochaSuiteFn('tracing/metrics_deactivated', function () {
+  this.timeout(config.getTestTimeout() * 2);
+
+  globalAgent.setUpCleanUpHooks();
+  const agentControls = globalAgent.instance;
+
+  describe('when tracing is enabled', function () {
+    let controls;
+
+    before(async () => {
+      controls = new ProcessControls({
+        dirname: __dirname,
+        useGlobalAgent: true,
+        env: {
+          INSTANA_DISABLE_METRICS: 'true',
+          INSTANA_DEBUG: 'true'
+        }
+      });
+
+      await controls.startAndWaitForAgentConnection();
+    });
+
+    beforeEach(async () => {
+      await agentControls.clearReceivedData();
+    });
+
+    after(async () => {
+      await controls.stop();
+    });
+
+    it('should still trace spans', async () => {
+      const response = await controls.sendRequest({
+        method: 'POST',
+        path: '/create-spans'
+      });
+
+      expect(response.message).to.equal('OK');
+      await testUtils.retry(async () => {
+        const spans = await agentControls.getSpans();
+        expect(spans.length).to.equal(2);
+      });
+    });
+  });
+});