feat: make dispatcher truly global (nodejs#1405)

* Make the dispatcher truly global

* make sure the global dispatcher is used for Node.js fetch

* Fix test

* added version number

.husky/pre-commit

@@ -2,4 +2,4 @@
 . "$(dirname "$0")/_/husky.sh"
 
 npm run lint
-npm run test
+npm run test

index-fetch.js

@@ -1,12 +1,10 @@
 'use strict'
 
-const Agent = require('./lib/agent')
-
-const globalDispatcher = new Agent()
-
+const { getGlobalDispatcher } = require('./lib/global')
 const fetchImpl = require('./lib/fetch')
+
 module.exports.fetch = async function fetch (resource) {
-  return fetchImpl.apply(globalDispatcher, arguments)
+  return fetchImpl.apply(getGlobalDispatcher(), arguments)
 }
 module.exports.FormData = require('./lib/fetch/formdata').FormData
 module.exports.Headers = require('./lib/fetch/headers').Headers

index.js

@@ -15,6 +15,7 @@ const MockAgent = require('./lib/mock/mock-agent')
 const MockPool = require('./lib/mock/mock-pool')
 const mockErrors = require('./lib/mock/mock-errors')
 const ProxyAgent = require('./lib/proxy-agent')
+const { getGlobalDispatcher, setGlobalDispatcher } = require('./lib/global')
 
 const nodeVersion = process.versions.node.split('.')
 const nodeMajor = Number(nodeVersion[0])
@@ -32,19 +33,6 @@ module.exports.ProxyAgent = ProxyAgent
 module.exports.buildConnector = buildConnector
 module.exports.errors = errors
 
-let globalDispatcher = new Agent()
-
-function setGlobalDispatcher (agent) {
-  if (!agent || typeof agent.dispatch !== 'function') {
-    throw new InvalidArgumentError('Argument agent must implement Agent')
-  }
-  globalDispatcher = agent
-}
-
-function getGlobalDispatcher () {
-  return globalDispatcher
-}
-
 function makeDispatcher (fn) {
   return (url, opts, handler) => {
     if (typeof opts === 'function') {

lib/global.js

@@ -0,0 +1,32 @@
+'use strict'
+
+// We include a version number for the Dispatcher API. In case of breaking changes,
+// this version number must be increased to avoid conflicts.
+const globalDispatcher = Symbol.for('undici.globalDispatcher.1')
+const { InvalidArgumentError } = require('./core/errors')
+const Agent = require('./agent')
+
+if (getGlobalDispatcher() === undefined) {
+  setGlobalDispatcher(new Agent())
+}
+
+function setGlobalDispatcher (agent) {
+  if (!agent || typeof agent.dispatch !== 'function') {
+    throw new InvalidArgumentError('Argument agent must implement Agent')
+  }
+  Object.defineProperty(globalThis, globalDispatcher, {
+    value: agent,
+    writable: true,
+    enumerable: false,
+    configurable: false
+  })
+}
+
+function getGlobalDispatcher () {
+  return globalThis[globalDispatcher]
+}
+
+module.exports = {
+  setGlobalDispatcher,
+  getGlobalDispatcher
+}

package.json

@@ -79,6 +79,7 @@
     "formdata-node": "^4.3.1",
     "https-pem": "^2.0.0",
     "husky": "^7.0.2",
+    "import-fresh": "^3.3.0",
     "jest": "^28.0.1",
     "jsfuzz": "^1.0.15",
     "mocha": "^10.0.0",

test/agent.js

@@ -10,8 +10,10 @@ const {
   request,
   stream,
   pipeline,
-  setGlobalDispatcher
+  setGlobalDispatcher,
+  getGlobalDispatcher
 } = require('../')
+const importFresh = require('import-fresh')
 
 test('setGlobalDispatcher', t => {
   t.plan(2)
@@ -645,34 +647,6 @@ test('drain', t => {
   })
 })
 
-// Port 80 is no accessible on CI.
-// test('agent works with port 80', t => {
-//   t.plan(1)
-
-//   const server = http.createServer((req, res) => {
-//     res.setHeader('Content-Type', 'text/plain')
-//     res.end()
-//   })
-
-//   t.teardown(server.close.bind(server))
-
-//   server.listen(80, async () => {
-//     const dispatcher = new Agent()
-
-//     const origin = `http://localhost:${server.address().port}`
-
-//     try {
-//       const { body } = await dispatcher.request({ origin, method: 'GET', path: '/' })
-
-//       body.on('end', () => {
-//         t.pass()
-//       }).resume()
-//     } catch (err) {
-//       t.error(err)
-//     }
-//   })
-// })
-
 test('global api', t => {
   t.plan(6 * 2)
 
@@ -724,3 +698,10 @@ test('connect is not valid', t => {
 
   t.throws(() => new Agent({ connect: false }), errors.InvalidArgumentError, 'connect must be a function or an object')
 })
+
+test('the dispatcher is truly global', t => {
+  const agent = getGlobalDispatcher()
+  const undiciFresh = importFresh('../index.js')
+  t.equal(agent, undiciFresh.getGlobalDispatcher())
+  t.end()
+})