perf(http2): reduce writeH2 per-request callback allocations

lib/dispatcher/client-h2.js

@@ -44,6 +44,8 @@ const kOpenStreams = Symbol('open streams')
 const kRequestStreamId = Symbol('request stream id')
 const kRequestStream = Symbol('request stream')
 const kRequestStreamCleanup = Symbol('request stream cleanup')
+const kRequestStreamOnData = Symbol('request stream on data')
+const kRequestStreamOnCloseError = Symbol('request stream on close error')
 const kReceivedGoAway = Symbol('received goaway')
 
 let extractBody
@@ -491,6 +493,37 @@ function onSocketClose () {
   this[kClosed] = true
 }
 
+function noop () {}
+
+function closeStreamSession (stream) {
+  const session = stream[kHTTP2Session]
+
+  stream[kHTTP2Session] = null
+  session[kOpenStreams] -= 1
+  if (session[kOpenStreams] === 0) {
+    session.unref()
+  }
+}
+
+function onUpgradeStreamClose () {
+  this.off('error', noop)
+
+  const failUpgradeStream = this[kRequestStreamOnCloseError]
+  this[kRequestStreamOnCloseError] = null
+
+  failUpgradeStream(new InformationalError('HTTP/2: stream closed before response headers'))
+  closeStreamSession(this)
+}
+
+function onRequestStreamClose () {
+  const onData = this[kRequestStreamOnData]
+
+  this[kRequestStreamOnData] = null
+  this.off('data', onData)
+  this.off('error', noop)
+  closeStreamSession(this)
+}
+
 // https://www.rfc-editor.org/rfc/rfc7230#section-3.3.2
 function shouldSendContentLength (method) {
   return method !== 'GET' && method !== 'HEAD' && method !== 'OPTIONS' && method !== 'TRACE' && method !== 'CONNECT'
@@ -623,14 +656,13 @@ function writeH2 (client, request) {
 
     const setupUpgradeStream = (stream) => {
       let responseReceived = false
-      const onDetachedUpgradeStreamError = () => {}
 
       const removeUpgradeStreamListeners = () => {
         stream.off('response', onUpgradeResponse)
         stream.off('error', onUpgradeStreamError)
         stream.off('end', onUpgradeStreamEnd)
         stream.off('timeout', onUpgradeStreamTimeout)
-        stream.off('error', onDetachedUpgradeStreamError)
+        stream.off('error', noop)
       }
 
       const releaseUpgradeStream = () => {
@@ -641,7 +673,7 @@ function writeH2 (client, request) {
         removeUpgradeStreamListeners()
 
         if (!stream.destroyed && !stream.closed) {
-          stream.once('error', onDetachedUpgradeStreamError)
+          stream.once('error', noop)
         }
       }
 
@@ -691,13 +723,9 @@ function writeH2 (client, request) {
       stream.on('error', onUpgradeStreamError)
       stream.once('end', onUpgradeStreamEnd)
       stream.on('timeout', onUpgradeStreamTimeout)
-      stream.once('close', () => {
-        stream.off('error', onDetachedUpgradeStreamError)
-        failUpgradeStream(new InformationalError('HTTP/2: stream closed before response headers'))
-
-        session[kOpenStreams] -= 1
-        if (session[kOpenStreams] === 0) session.unref()
-      })
+      stream[kHTTP2Session] = session
+      stream[kRequestStreamOnCloseError] = failUpgradeStream
+      stream.once('close', onUpgradeStreamClose)
 
       ++session[kOpenStreams]
       stream.setTimeout(requestTimeout)
@@ -855,7 +883,6 @@ function writeH2 (client, request) {
 
   // Track whether we received a response (headers)
   let responseReceived = false
-  const onDetachedStreamError = () => {}
   const onData = (chunk) => {
     if (request.aborted || request.completed) {
       return
@@ -867,7 +894,7 @@ function writeH2 (client, request) {
   }
 
   const removeRequestStreamListeners = () => {
-    stream.off('error', onDetachedStreamError)
+    stream.off('error', noop)
     stream.off('continue', writeBodyH2)
     stream.off('response', onResponse)
     stream.off('end', onEnd)
@@ -887,7 +914,7 @@ function writeH2 (client, request) {
     removeRequestStreamListeners()
 
     if (!stream.destroyed && !stream.closed) {
-      stream.once('error', onDetachedStreamError)
+      stream.once('error', noop)
     }
   }
 
@@ -933,14 +960,9 @@ function writeH2 (client, request) {
     }
   }
 
-  stream.once('close', () => {
-    stream.off('data', onData)
-    stream.off('error', onDetachedStreamError)
-    session[kOpenStreams] -= 1
-    if (session[kOpenStreams] === 0) {
-      session.unref()
-    }
-  })
+  stream[kHTTP2Session] = session
+  stream[kRequestStreamOnData] = onData
+  stream.once('close', onRequestStreamClose)
 
   const onError = function (err) {
     stream.off('error', onError)