feat: add OPENTELEMETRY_NO_PATCH_MODULES (open-telemetry#1153)

Co-authored-by: Daniel Dyla <dyladan@users.noreply.github.com>
srikanthccv · Jun 12, 2020 · 8c56442 · 8c56442
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diff --git a/packages/opentelemetry-node/README.md b/packages/opentelemetry-node/README.md
@@ -102,6 +102,14 @@ const provider = new NodeTracerProvider({
 });
 ```
 
+### Disable Plugins with Environment Variables
+
+Plugins can be disabled without modifying and redeploying code.
+`OTEL_NO_PATCH_MODULES` accepts a
+comma separated list of module names to disabled specific plugins.
+The names should match what you use to `require` the module into your application.
+For example, `OTEL_NO_PATCH_MODULES=pg,https` will disable the postgres plugin and the https plugin. To disable **all** plugins, set the environment variable to `*`.
+
 ## Examples
 
 See how to automatically instrument [http](https://github.com/open-telemetry/opentelemetry-js/tree/master/examples/http) and [gRPC](https://github.com/open-telemetry/opentelemetry-js/tree/master/examples/grpc) using node-sdk.

diff --git a/packages/opentelemetry-node/src/instrumentation/PluginLoader.ts b/packages/opentelemetry-node/src/instrumentation/PluginLoader.ts
@@ -30,6 +30,17 @@ export enum HookState {
   DISABLED,
 }
 
+/**
+ * Environment variable which will contain list of modules to not load corresponding plugins for
+ * e.g.OTEL_NO_PATCH_MODULES=pg,https,mongodb
+ */
+export const ENV_PLUGIN_DISABLED_LIST = 'OTEL_NO_PATCH_MODULES';
+
+/**
+ * Wildcard symbol. If ignore list is set to this, disable all plugins
+ */
+const DISABLE_ALL_PLUGINS = '*';
+
 export interface Plugins {
   [pluginName: string]: PluginConfig;
 }
@@ -46,6 +57,18 @@ function filterPlugins(plugins: Plugins): Plugins {
   }, {});
 }
 
+/**
+ * Parse process.env[ENV_PLUGIN_DISABLED_LIST] for a list of modules
+ * not to load corresponding plugins for.
+ */
+function getIgnoreList(): string[] | typeof DISABLE_ALL_PLUGINS {
+  const envIgnoreList: string = process.env[ENV_PLUGIN_DISABLED_LIST] || '';
+  if (envIgnoreList === DISABLE_ALL_PLUGINS) {
+    return envIgnoreList;
+  }
+  return envIgnoreList.split(',').map(v => v.trim());
+}
+
 /**
  * The PluginLoader class can load instrumentation plugins that use a patch
  * mechanism to enable automatic tracing for specific target modules.
@@ -74,6 +97,7 @@ export class PluginLoader {
     if (this._hookState === HookState.UNINITIALIZED) {
       const pluginsToLoad = filterPlugins(plugins);
       const modulesToHook = Object.keys(pluginsToLoad);
+      const modulesToIgnore = getIgnoreList();
       // Do not hook require when no module is provided. In this case it is
       // not necessary. With skipping this step we lower our footprint in
       // customer applications and require-in-the-middle won't show up in CPU
@@ -119,6 +143,21 @@ export class PluginLoader {
           version = utils.getPackageVersion(this.logger, baseDir);
         }
 
+        // Skip loading of all modules if '*' is provided
+        if (modulesToIgnore === DISABLE_ALL_PLUGINS) {
+          this.logger.info(
+            `PluginLoader#load: skipped patching module ${name} because all plugins are disabled (${ENV_PLUGIN_DISABLED_LIST})`
+          );
+          return exports;
+        }
+
+        if (modulesToIgnore.includes(name)) {
+          this.logger.info(
+            `PluginLoader#load: skipped patching module ${name} because it was on the ignore list (${ENV_PLUGIN_DISABLED_LIST})`
+          );
+          return exports;
+        }
+
         this.logger.info(
           `PluginLoader#load: trying to load ${name}@${version}`
         );

diff --git a/packages/opentelemetry-node/test/instrumentation/PluginLoader.test.ts b/packages/opentelemetry-node/test/instrumentation/PluginLoader.test.ts
@@ -23,6 +23,7 @@ import {
   PluginLoader,
   Plugins,
   searchPathForTest,
+  ENV_PLUGIN_DISABLED_LIST,
 } from '../../src/instrumentation/PluginLoader';
 
 const INSTALLED_PLUGINS_PATH = path.join(__dirname, 'node_modules');
@@ -135,6 +136,10 @@ describe('PluginLoader', () => {
   });
 
   describe('.load()', () => {
+    afterEach(() => {
+      delete process.env[ENV_PLUGIN_DISABLED_LIST];
+    });
+
     it('sanity check', () => {
       // Ensure that module fixtures contain values that we expect.
       const simpleModule = require('simple-module');
@@ -152,6 +157,86 @@ describe('PluginLoader', () => {
       assert.throws(() => require('nonexistent-module'));
     });
 
+    it('should not load a plugin on the ignore list environment variable', () => {
+      // Set ignore list env var
+      process.env[ENV_PLUGIN_DISABLED_LIST] = 'simple-module';
+      const pluginLoader = new PluginLoader(provider, logger);
+      pluginLoader.load({ ...simplePlugins, ...supportedVersionPlugins });
+
+      assert.strictEqual(pluginLoader['_plugins'].length, 0);
+
+      const simpleModule = require('simple-module');
+      assert.strictEqual(pluginLoader['_plugins'].length, 0);
+      assert.strictEqual(simpleModule.value(), 0);
+      assert.strictEqual(simpleModule.name(), 'simple-module');
+
+      const supportedModule = require('supported-module');
+      assert.strictEqual(pluginLoader['_plugins'].length, 1);
+      assert.strictEqual(supportedModule.value(), 1);
+      assert.strictEqual(supportedModule.name(), 'patched-supported-module');
+
+      pluginLoader.unload();
+    });
+
+    it('should not load plugins on the ignore list environment variable', () => {
+      // Set ignore list env var
+      process.env[ENV_PLUGIN_DISABLED_LIST] = 'simple-module,http';
+      const pluginLoader = new PluginLoader(provider, logger);
+      pluginLoader.load({
+        ...simplePlugins,
+        ...supportedVersionPlugins,
+        ...httpPlugins,
+      });
+
+      assert.strictEqual(pluginLoader['_plugins'].length, 0);
+
+      const simpleModule = require('simple-module');
+      assert.strictEqual(pluginLoader['_plugins'].length, 0);
+      assert.strictEqual(simpleModule.value(), 0);
+      assert.strictEqual(simpleModule.name(), 'simple-module');
+
+      const httpModule = require('http');
+      assert.ok(httpModule);
+      assert.strictEqual(pluginLoader['_plugins'].length, 0);
+
+      const supportedModule = require('supported-module');
+      assert.strictEqual(pluginLoader['_plugins'].length, 1);
+      assert.strictEqual(supportedModule.value(), 1);
+      assert.strictEqual(supportedModule.name(), 'patched-supported-module');
+
+      pluginLoader.unload();
+    });
+
+    it('should not load any plugins if ignore list environment variable is set to "*"', () => {
+      // Set ignore list env var
+      process.env[ENV_PLUGIN_DISABLED_LIST] = '*';
+      const pluginLoader = new PluginLoader(provider, logger);
+      pluginLoader.load({
+        ...simplePlugins,
+        ...supportedVersionPlugins,
+        ...httpPlugins,
+      });
+
+      assert.strictEqual(pluginLoader['_plugins'].length, 0);
+
+      const simpleModule = require('simple-module');
+      const httpModule = require('http');
+      const supportedModule = require('supported-module');
+
+      assert.strictEqual(
+        pluginLoader['_plugins'].length,
+        0,
+        'No plugins were loaded'
+      );
+      assert.strictEqual(simpleModule.value(), 0);
+      assert.strictEqual(simpleModule.name(), 'simple-module');
+      assert.ok(httpModule);
+      assert.strictEqual(supportedModule.value(), 0);
+      assert.strictEqual(supportedModule.name(), 'supported-module');
+
+      pluginLoader.unload();
+    });
+
     it('should load a plugin and patch the target modules', () => {
       const pluginLoader = new PluginLoader(provider, logger);
       assert.strictEqual(pluginLoader['_plugins'].length, 0);