feat: provide global opt-out switch (DASH0_DISABLE)

README.md

@@ -18,6 +18,10 @@ This can be disabled either by setting `OTEL_SERVICE_NAME` or by setting `DASH0_
 
 Additional debug logs can be enabled by setting `DASH0_DEBUG=true`.
 
+### <a id="DASH0_DISABLE">DASH0_DISABLE</a>
+
+Disables the Dash0 Node.js distribution entirely.
+
 ### <a id="DASH0_ENABLE_FS_INSTRUMENTATION">DASH0_ENABLE_FS_INSTRUMENTATION</a>
 
 By default, the instrumentation plug-in `@opentelemetry/instrumentation-fs` is disabled. Set `DASH0_ENABLE_FS_INSTRUMENTATION=true` to enable spans for file system access.

src/index.ts

@@ -36,7 +36,11 @@ function init() {
   }
 }
 
-init();
+if (process.env.DASH0_DISABLE == null || process.env.DASH0_DISABLE.toLowerCase() !== 'true') {
+  init();
+} else {
+  logProhibitiveError(`The distribution has been disabled by setting DASH0_DISABLE=${process.env.DASH0_DISABLE}.`);
+}
 
 function logProhibitiveError(message: string) {
   console.error(`[${prefix}] ${message} OpenTelemetry data will not be sent to Dash0.`);

test/collector/CollectorChildProcessWrapper.ts

@@ -27,4 +27,8 @@ export default class CollectorChildProcessWrapper extends ChildProcessWrapper {
   async fetchTelemetry() {
     return <OpenTelemetryData>await collector().sendRequest({ command: 'telemetry' });
   }
+
+  async clear() {
+    await collector().sendRequest({ command: 'clear' });
+  }
 }

test/collector/Sink.ts

@@ -64,6 +64,14 @@ export default class Sink {
     return this.telemetry;
   }
 
+  clear() {
+    this.telemetry = {
+      traces: [],
+      metrics: [],
+      logs: [],
+    };
+  }
+
   printStats() {
     console.log(JSON.stringify(this.stats(), null, 2));
   }

test/collector/index.ts

@@ -34,6 +34,9 @@ function registerIpcMessageListener() {
       case 'telemetry':
         sendToParentProcess({ id, ...sink.getTelemetry() });
         break;
+      case 'clear':
+        sink.clear();
+        break;
       default:
         console.error(`Unknown message: ${inspect(message)}`);
     }

test/integration/rootHooks.ts

@@ -21,6 +21,10 @@ export const mochaHooks = {
     console.debug('[rootHooks] global mock collector started');
   },
 
+  async beforeEach() {
+    collectorInstance.clear();
+  },
+
   async afterAll() {
     console.debug('[rootHooks] stopping global mock collector');
     await collectorInstance.stop();

test/integration/test.ts

@@ -12,9 +12,12 @@ import runCommand from '../util/runCommand';
 import waitUntil from '../util/waitUntil';
 import ChildProcessWrapper, { defaultAppConfiguration } from './ChildProcessWrapper';
 import { collector } from './rootHooks';
+import delay from '../util/delay';
 
 const skipWhenNodeJsVersionIsSmallerThan = '18.0.0';
 
+const { fail } = expect;
+
 const appPort = 1302;
 let expectedDistroVersion: number;
 
@@ -104,7 +107,7 @@ describe('attach', () => {
       await appUnderTest.stop();
     });
 
-    it('should attach via --require and derive a service name from the package.json file ', async () => {
+    it('should attach via --require and derive a service name from the package.json file', async () => {
       await waitUntil(async () => {
         const telemetry = await waitForTelemetry();
         expectMatchingSpan(
@@ -122,6 +125,37 @@ describe('attach', () => {
     });
   });
 
+  describe('disable via DASH0_DISABLE', () => {
+    let appUnderTest: ChildProcessWrapper;
+
+    before(async () => {
+      const appConfiguration = defaultAppConfiguration(appPort);
+      if (!appConfiguration.env) {
+        appConfiguration.env = {};
+      }
+      appConfiguration.env.DASH0_DISABLE = 'true';
+      appUnderTest = new ChildProcessWrapper(appConfiguration);
+      await appUnderTest.start();
+    });
+
+    after(async () => {
+      await appUnderTest.stop();
+    });
+
+    it('should do nothing if disabled', async () => {
+      await delay(1000);
+      const response = await fetch(`http://localhost:${appPort}/ohai`);
+      await delay(2000);
+      expect(response.status).to.equal(200);
+      const responsePayload = await response.json();
+      expect(responsePayload).to.deep.equal({ message: 'We make Observability easy for every developer.' });
+
+      if (await collector().hasTelemetry()) {
+        fail('The collector received telemetry data although it should not have received anything.');
+      }
+    });
+  });
+
   async function waitForTelemetry() {
     const response = await fetch(`http://localhost:${appPort}/ohai`);
     expect(response.status).to.equal(200);