Remove FinalizationRegistry from Agent

lib/agent.js

@@ -1,22 +1,21 @@
 'use strict'
 
 const { InvalidArgumentError } = require('./core/errors')
-const { kClients, kRunning, kClose, kDestroy, kDispatch, kInterceptors } = require('./core/symbols')
+const { kClients, kRunning, kClose, kDestroy, kDispatch, kInterceptors, kBusy } = require('./core/symbols')
 const DispatcherBase = require('./dispatcher-base')
 const Pool = require('./pool')
 const Client = require('./client')
 const util = require('./core/util')
 const createRedirectInterceptor = require('./interceptor/redirectInterceptor')
-const { WeakRef, FinalizationRegistry } = require('./compat/dispatcher-weakref')()
 
 const kOnConnect = Symbol('onConnect')
 const kOnDisconnect = Symbol('onDisconnect')
 const kOnConnectionError = Symbol('onConnectionError')
 const kMaxRedirections = Symbol('maxRedirections')
 const kOnDrain = Symbol('onDrain')
 const kFactory = Symbol('factory')
-const kFinalizer = Symbol('finalizer')
 const kOptions = Symbol('options')
+const kDeleteScheduled = Symbol('deleteScheduled')
 
 function defaultFactory (origin, opts) {
   return opts && opts.connections === 1
@@ -55,12 +54,6 @@ class Agent extends DispatcherBase {
     this[kMaxRedirections] = maxRedirections
     this[kFactory] = factory
     this[kClients] = new Map()
-    this[kFinalizer] = new FinalizationRegistry(/* istanbul ignore next: gc is undeterministic */ key => {
-      const ref = this[kClients].get(key)
-      if (ref !== undefined && ref.deref() === undefined) {
-        this[kClients].delete(key)
-      }
-    })
 
     const agent = this
 
@@ -83,12 +76,8 @@ class Agent extends DispatcherBase {
 
   get [kRunning] () {
     let ret = 0
-    for (const ref of this[kClients].values()) {
-      const client = ref.deref()
-      /* istanbul ignore next: gc is undeterministic */
-      if (client) {
-        ret += client[kRunning]
-      }
+    for (const client of this[kClients].values()) {
+      ret += client[kRunning]
     }
     return ret
   }
@@ -101,47 +90,59 @@ class Agent extends DispatcherBase {
       throw new InvalidArgumentError('opts.origin must be a non-empty string or URL.')
     }
 
-    const ref = this[kClients].get(key)
+    let dispatcher = this[kClients].get(key)
 
-    let dispatcher = ref ? ref.deref() : null
     if (!dispatcher) {
       dispatcher = this[kFactory](opts.origin, this[kOptions])
-        .on('drain', this[kOnDrain])
+        .on('drain', (...args) => {
+          this[kOnDrain](...args)
+
+          // We remove the client if it is not busy for 5 minutes
+          // to avoid a long list of clients to saturate memory.
+          // Ideally, we could use a FinalizationRegistry here, but
+          // it is currently very buggy in Node.js.
+          // See
+          // * https://github.com/nodejs/node/issues/49344
+          // * https://github.com/nodejs/node/issues/47748
+          // TODO(mcollina): make the timeout configurable or
+          // use an event to remove disconnected clients.
+          this[kDeleteScheduled] = setTimeout(() => {
+            if (dispatcher[kBusy] === 0) {
+              this[kClients].destroy().then(() => {})
+              this[kClients].delete(key)
+            }
+          }, 300_000)
+          this[kDeleteScheduled].unref()
+        })
         .on('connect', this[kOnConnect])
         .on('disconnect', this[kOnDisconnect])
         .on('connectionError', this[kOnConnectionError])
 
-      this[kClients].set(key, new WeakRef(dispatcher))
-      this[kFinalizer].register(dispatcher, key)
+      this[kClients].set(key, dispatcher)
+    } else if (dispatcher[kDeleteScheduled]) {
+      clearTimeout(dispatcher[kDeleteScheduled])
+      dispatcher[kDeleteScheduled] = null
     }
 
     return dispatcher.dispatch(opts, handler)
   }
 
   async [kClose] () {
     const closePromises = []
-    for (const ref of this[kClients].values()) {
-      const client = ref.deref()
-      /* istanbul ignore else: gc is undeterministic */
-      if (client) {
-        this[kFinalizer].unregister(client)
-        closePromises.push(client.close())
-      }
+    for (const client of this[kClients].values()) {
+      closePromises.push(client.close())
     }
+    this[kClients].clear()
 
     await Promise.all(closePromises)
   }
 
   async [kDestroy] (err) {
     const destroyPromises = []
-    for (const ref of this[kClients].values()) {
-      const client = ref.deref()
-      /* istanbul ignore else: gc is undeterministic */
-      if (client) {
-        this[kFinalizer].unregister(client)
-        destroyPromises.push(client.destroy(err))
-      }
+    for (const client of this[kClients].values()) {
+      destroyPromises.push(client.destroy(err))
     }
+    this[kClients].clear()
 
     await Promise.all(destroyPromises)
   }

lib/mock/mock-agent.js

@@ -21,16 +21,6 @@ const Dispatcher = require('../dispatcher')
 const Pluralizer = require('./pluralizer')
 const PendingInterceptorsFormatter = require('./pending-interceptors-formatter')
 
-class FakeWeakRef {
-  constructor (value) {
-    this.value = value
-  }
-
-  deref () {
-    return this.value
-  }
-}
-
 class MockAgent extends Dispatcher {
   constructor (opts) {
     super(opts)
@@ -103,7 +93,7 @@ class MockAgent extends Dispatcher {
   }
 
   [kMockAgentSet] (origin, dispatcher) {
-    this[kClients].set(origin, new FakeWeakRef(dispatcher))
+    this[kClients].set(origin, dispatcher)
   }
 
   [kFactory] (origin) {
@@ -115,9 +105,9 @@ class MockAgent extends Dispatcher {
 
   [kMockAgentGet] (origin) {
     // First check if we can immediately find it
-    const ref = this[kClients].get(origin)
-    if (ref) {
-      return ref.deref()
+    const client = this[kClients].get(origin)
+    if (client) {
+      return client
     }
 
     // If the origin is not a string create a dummy parent pool and return to user
@@ -128,8 +118,7 @@ class MockAgent extends Dispatcher {
     }
 
     // If we match, create a pool and assign the same dispatches
-    for (const [keyMatcher, nonExplicitRef] of Array.from(this[kClients])) {
-      const nonExplicitDispatcher = nonExplicitRef.deref()
+    for (const [keyMatcher, nonExplicitDispatcher] of Array.from(this[kClients])) {
       if (nonExplicitDispatcher && typeof keyMatcher !== 'string' && matchValue(keyMatcher, origin)) {
         const dispatcher = this[kFactory](origin)
         this[kMockAgentSet](origin, dispatcher)
@@ -147,7 +136,7 @@ class MockAgent extends Dispatcher {
     const mockAgentClients = this[kClients]
 
     return Array.from(mockAgentClients.entries())
-      .flatMap(([origin, scope]) => scope.deref()[kDispatches].map(dispatch => ({ ...dispatch, origin })))
+      .flatMap(([origin, scope]) => scope[kDispatches].map(dispatch => ({ ...dispatch, origin })))
       .filter(({ pending }) => pending)
   }