Add support for disabling plugins by environment variable

docs/API.md

@@ -328,6 +328,7 @@ Options can be configured as a parameter to the [init()](./interfaces/tracer.htm
 | reportHostname | `DD_TRACE_REPORT_HOSTNAME`     | `false`     | Whether to report the system's hostname for each trace. When disabled, the hostname of the agent will be used instead. |
 | experimental   | -                              | `{}`        | Experimental features can be enabled all at once using boolean `true` or individually using key/value pairs. Please contact us to learn more about the available experimental features. |
 | plugins        | -                              | `true`      | Whether or not to enable automatic instrumentation of external libraries using the built-in plugins. |
+| -              | `DD_TRACE_DISABLED_PLUGINS`    | -           | A comma-separated string of integration names automatically disabled when tracer is initialized. Environment variable only e.g. `DD_TRACE_DISABLED_PLUGINS=express,dns`. |
 | clientToken    | `DD_CLIENT_TOKEN`              | -           | Client token for browser tracing. Can be generated in the UI at `Integrations -> APIs`. |
 | logLevel       | `DD_TRACE_LOG_LEVEL`           | `debug`     | A string for the minimum log level for the tracer to use when debug logging is enabled, e.g. `'error'`, `'debug'`. |
 

packages/dd-trace/src/instrumenter.js

@@ -8,6 +8,12 @@ shimmer({ logger: () => {} })
 
 const plugins = platform.plugins
 
+const disabldPlugins = platform.env('DD_TRACE_DISABLED_PLUGINS')
+
+const collectDisabledPlugins = () => {
+  return new Set(disabldPlugins && disabldPlugins.split(',').map(plugin => plugin.trim()))
+}
+
 class Instrumenter {
   constructor (tracer) {
     this._tracer = tracer
@@ -16,6 +22,7 @@ class Instrumenter {
     this._names = new Set()
     this._plugins = new Map()
     this._instrumented = new Map()
+    this._disabledPlugins = collectDisabledPlugins()
   }
 
   use (name, config) {
@@ -149,8 +156,12 @@ class Instrumenter {
   }
 
   _set (plugin, meta) {
-    this._plugins.set(plugin, meta)
-    this.load(plugin, meta)
+    if (this._disabledPlugins.has(meta.name)) {
+      log.debug(`Plugin "${meta.name}" was disabled via configuration option.`)
+    } else {
+      this._plugins.set(plugin, meta)
+      this.load(plugin, meta)
+    }
   }
 }
 

packages/dd-trace/test/instrumenter.spec.js

@@ -352,4 +352,73 @@ describe('Instrumenter', () => {
       })
     })
   })
+
+  describe('with plugins disabled via DD_TRACE_DISABLED_PLUGINS environment variable', () => {
+    beforeEach(() => {
+      process.env.DD_TRACE_DISABLED_PLUGINS = 'http,mysql-mock'
+
+      Instrumenter = proxyquire('../src/instrumenter', {
+        'shimmer': shimmer,
+        './platform': {
+          plugins: {
+            'http': integrations.http,
+            'express-mock': integrations.express,
+            'mysql-mock': integrations.mysql,
+            'other': integrations.other
+          }
+        },
+        '../../datadog-plugin-http/src': integrations.http,
+        '../../datadog-plugin-express-mock/src': integrations.express,
+        '../../datadog-plugin-mysql-mock/src': integrations.mysql,
+        '../../datadog-plugin-other/src': integrations.other
+      })
+
+      instrumenter = new Instrumenter(tracer)
+    })
+
+    afterEach(() => {
+      delete process.env.DD_TRACE_DISABLED_PLUGINS
+    })
+
+    describe('enable', () => {
+      it('should not patch plugins disabled from environnment variable configuration option', () => {
+        instrumenter.enable()
+
+        require('http')
+        require('mysql-mock')
+
+        expect(integrations.http.patch).to.not.have.been.called
+        expect(integrations.mysql[0].patch).to.not.have.been.called
+        expect(integrations.mysql[1].patch).to.not.have.been.called
+      })
+
+      it('should patch plugins not disabled by environnment variable configuration option', () => {
+        const configDefault = {}
+        instrumenter.enable()
+
+        const express = require('express-mock')
+
+        expect(integrations.express.patch).to.have.been.calledWith(express, 'tracer', configDefault)
+        expect(process.env.DD_TRACE_DISABLED_PLUGINS.indexOf('express-mock')).to.equal(-1)
+      })
+
+      it('should not patch plugins called by .use that have been disabled by environment variable', () => {
+        const configDefault = {}
+
+        instrumenter.use('http', configDefault)
+        instrumenter.use('mysql-mock', configDefault)
+        instrumenter.use('express-mock', configDefault)
+        instrumenter.enable()
+
+        const express = require('express-mock')
+        require('http')
+        require('mysql-mock')
+
+        expect(integrations.express.patch).to.have.been.calledWith(express, 'tracer', configDefault)
+        expect(integrations.http.patch).to.not.have.been.called
+        expect(integrations.mysql[0].patch).to.not.have.been.called
+        expect(integrations.mysql[1].patch).to.not.have.been.called
+      })
+    })
+  })
 })