fix: memory leak in Agent

Author: hexchain

lib/dispatcher/agent.js

@@ -45,22 +45,10 @@ class Agent extends DispatcherBase {
     }
 
     this[kOnConnect] = (origin, targets) => {
-      const result = this[kClients].get(origin)
-      if (result) {
-        result.count += 1
-      }
       this.emit('connect', origin, [this, ...targets])
     }
 
     this[kOnDisconnect] = (origin, targets, err) => {
-      const result = this[kClients].get(origin)
-      if (result) {
-        result.count -= 1
-        if (result.count <= 0) {
-          this[kClients].delete(origin)
-          result.dispatcher.destroy()
-        }
-      }
       this.emit('disconnect', origin, [this, ...targets], err)
     }
 
@@ -91,8 +79,24 @@ class Agent extends DispatcherBase {
     if (!dispatcher) {
       dispatcher = this[kFactory](opts.origin, this[kOptions])
         .on('drain', this[kOnDrain])
-        .on('connect', this[kOnConnect])
-        .on('disconnect', this[kOnDisconnect])
+        .on('connect', (origin, targets) => {
+          const result = this[kClients].get(key)
+          if (result) {
+            result.count += 1
+          }
+          this[kOnConnect](origin, targets)
+        })
+        .on('disconnect', (origin, targets, err) => {
+          const result = this[kClients].get(key)
+          if (result) {
+            result.count -= 1
+            if (result.count <= 0) {
+              this[kClients].delete(key)
+              result.dispatcher.destroy()
+            }
+          }
+          this[kOnDisconnect](origin, targets, err)
+        })
         .on('connectionError', this[kOnConnectionError])
 
       this[kClients].set(key, { count: 0, dispatcher })

test/issue-4244.js

@@ -0,0 +1,35 @@
+const { test } = require('node:test')
+const assert = require('node:assert')
+const { createServer } = require('node:http')
+const { request, Agent, Pool } = require('..')
+
+// https://github.com/nodejs/undici/issues/4424
+test('Agent should destroy clients of origins without active connections', async (t) => {
+  const server = createServer({ keepAliveTimeout: 0 }, async (_req, res) => {
+    res.setHeader('connection', 'close')
+    res.writeHead(200)
+    res.end('ok')
+  }).listen(0)
+
+  t.after(() => server.close())
+
+  let p
+  const agent = new Agent({
+    factory: (origin, opts) => {
+      const pool = new Pool(origin, opts)
+      let _resolve, _reject
+      p = new Promise((resolve, reject) => {
+        _resolve = resolve
+        _reject = reject
+      })
+      pool.on('disconnect', () => {
+        setImmediate(() => pool.destroyed ? _resolve() : _reject(new Error('client not destroyed')))
+      })
+      return pool
+    }
+  })
+  const { statusCode } = await request(`http://localhost:${server.address().port}`, { dispatcher: agent })
+  assert.equal(statusCode, 200)
+
+  await p
+})