feat: Added instrumentation for fetch. (#1776)

THIRD_PARTY_NOTICES.md

@@ -2218,7 +2218,7 @@ THE SOFTWARE.
 
 ### c8
 
-This product includes source derived from [c8](https://github.com/bcoe/c8) ([v7.14.0](https://github.com/bcoe/c8/tree/v7.14.0)), distributed under the [ISC License](https://github.com/bcoe/c8/blob/v7.14.0/LICENSE.txt):
+This product includes source derived from [c8](https://github.com/bcoe/c8) ([v8.0.1](https://github.com/bcoe/c8/tree/v8.0.1)), distributed under the [ISC License](https://github.com/bcoe/c8/blob/v8.0.1/LICENSE.txt):
 
 ```
 Copyright (c) 2017, Contributors

lib/instrumentation/undici.js

@@ -14,25 +14,36 @@ const symbols = require('../symbols')
 const { executionAsyncResource } = require('async_hooks')
 const diagnosticsChannel = require('diagnostics_channel')
 
-module.exports = function addUndiciChannels(agent, _undici, _modName, shim) {
-  registerHookPoints(shim)
-}
+const channels = [
+  { channel: diagnosticsChannel.channel('undici:request:create'), hook: requestCreateHook },
+  { channel: diagnosticsChannel.channel('undici:request:headers'), hook: requestHeadersHook },
+  { channel: diagnosticsChannel.channel('undici:request:trailers'), hook: endAndRestoreSegment },
+  { channel: diagnosticsChannel.channel('undici:request:error'), hook: endAndRestoreSegment }
+]
 
 /**
  * Subscribes to all relevant undici hook points
  * See: https://github.com/nodejs/undici/blob/main/docs/api/DiagnosticsChannel.md
  *
- * @param {Shim} shim instance of shim
+ * @param agent
+ * @param _undici
+ * @param _modName
+ * @param shim
  */
-function registerHookPoints(shim) {
-  const requestCreate = diagnosticsChannel.channel('undici:request:create')
-  requestCreate.subscribe(requestCreateHook.bind(null, shim))
-  const requestHeaders = diagnosticsChannel.channel('undici:request:headers')
-  requestHeaders.subscribe(requestHeadersHook.bind(null, shim))
-  const requestTrailers = diagnosticsChannel.channel('undici:request:trailers')
-  requestTrailers.subscribe(endAndRestoreSegment.bind(null, shim))
-  const requestError = diagnosticsChannel.channel('undici:request:error')
-  requestError.subscribe(endAndRestoreSegment.bind(null, shim))
+module.exports = function addUndiciChannels(agent, _undici, _modName, shim) {
+  channels.forEach(({ channel, hook }) => {
+    if (!channel.hasSubscribers) {
+      channel.subscribe(hook.bind(null, shim))
+    }
+  })
+}
+
+module.exports.unsubscribe = function unsubscribe() {
+  channels.forEach(({ channel, hook }) => {
+    if (channel.hasSubscribers) {
+      channel.unsubscribe(hook)
+    }
+  })
 }
 
 /**
@@ -107,6 +118,9 @@ function addDTHeaders({ transaction, config, request }) {
 function createExternalSegment({ shim, request, parentSegment }) {
   const url = new URL(request.origin + request.path)
   const name = NAMES.EXTERNAL.PREFIX + url.host + url.pathname
+  // Metrics for `External/<host>` will have a suffix of undici
+  // We will have to see if this matters for people only using fetch
+  // It's undici under the hood so ¯\_(ツ)_/¯
   const segment = shim.createSegment(name, recordExternal(url.host, 'undici'), parentSegment)
   if (segment) {
     segment.start()

lib/instrumentations.js

@@ -36,7 +36,6 @@ module.exports = function instrumentations() {
     '@redis/client': { type: MODULE_TYPE.DATASTORE },
     'restify': { type: MODULE_TYPE.WEB_FRAMEWORK },
     'superagent': { module: '@newrelic/superagent' },
-    'undici': { type: MODULE_TYPE.TRANSACTION },
     '@hapi/vision': { type: MODULE_TYPE.WEB_FRAMEWORK },
     'when': { module: './instrumentation/when' },
     'winston': { type: MODULE_TYPE.GENERIC },

lib/shimmer.js

@@ -18,6 +18,7 @@ let pkgsToHook = []
 
 const NAMES = require('./metrics/names')
 const symbols = require('./symbols')
+const { unsubscribe } = require('./instrumentation/undici')
 
 const MODULE_TYPE = shims.constants.MODULE_TYPE
 
@@ -328,6 +329,12 @@ const shimmer = (module.exports = {
     const globalsFilepath = path.join(__dirname, 'instrumentation', 'core', 'globals.js')
     _firstPartyInstrumentation(agent, globalsFilepath, globalShim, global, 'globals')
 
+    // Since this just registers subscriptions to diagnostics_channel events from undici
+    // We register this as core and it'll work for both fetch and undici
+    const undiciPath = path.join(__dirname, 'instrumentation', 'undici.js')
+    const undiciShim = shims.createShimFromType(MODULE_TYPE.TRANSACTION, agent, 'undici', 'undici')
+    _firstPartyInstrumentation(agent, undiciPath, undiciShim)
+
     // Instrument each of the core modules.
     for (const [mojule, core] of Object.entries(CORE_INSTRUMENTATION)) {
       const filePath = path.join(__dirname, 'instrumentation', 'core', core.file)
@@ -364,6 +371,7 @@ const shimmer = (module.exports = {
     }
 
     pkgsToHook = []
+    unsubscribe()
   },
 
   bootstrapInstrumentation: function bootstrapInstrumentation(agent) {