http: add drop request event for http server

PR-URL: #43806 Reviewed-By: Matteo Collina <[email protected]>

Author: theanarkh

doc/api/http.md

@@ -1396,6 +1396,20 @@ This event is guaranteed to be passed an instance of the{net.Socket} class,
 a subclass of{stream.Duplex}, unless the user specifies a socket
 type other than{net.Socket}.
 
+### Event: `'dropRequest'`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+*`request`{http.IncomingMessage} Arguments for the HTTP request, as it is in
+ the [`'request'`][] event
+*`socket`{stream.Duplex} Network socket between the server and client
+
+When the number of requests on a socket reaches the threshold of
+`server.maxRequestsPerSocket`, the server will drop new requests
+and emit `'dropRequest'` event instead, then send `503` to client.
+
 ### Event: `'request'`
 
 <!-- YAML

lib/_http_server.js

@@ -951,7 +951,7 @@ function parserOnIncoming(server, socket, state, req, keepAlive){
 if(isRequestsLimitSet&&
 (server.maxRequestsPerSocket<state.requestsCount)){
 handled=true;
-
+server.emit('dropRequest',req,socket);
 res.writeHead(503);
 res.end();
 }elseif(req.headers.expect!==undefined){

test/parallel/test-http-keep-alive-drop-requests.js

@@ -0,0 +1,34 @@
+'use strict';
+
+constcommon=require('../common');
+consthttp=require('http');
+constnet=require('net');
+constassert=require('assert');
+
+functionrequest(socket){
+socket.write('GET / HTTP/1.1\r\n');
+socket.write('Connection: keep-alive\r\n');
+socket.write('\r\n\r\n');
+}
+
+constserver=http.createServer(common.mustCall((req,res)=>{
+res.end('ok');
+}));
+
+server.on('dropRequest',common.mustCall((request,socket)=>{
+assert.strictEqual(requestinstanceofhttp.IncomingMessage,true);
+assert.strictEqual(socketinstanceofnet.Socket,true);
+server.close();
+}));
+
+server.listen(0,common.mustCall(()=>{
+constsocket=net.connect(server.address().port);
+socket.on('connect',common.mustCall(()=>{
+request(socket);
+request(socket);
+}));
+socket.on('data',common.mustCallAtLeast());
+socket.on('close',common.mustCall());
+}));
+
+server.maxRequestsPerSocket=1;

test/parallel/test-https-keep-alive-drop-requests.js

@@ -0,0 +1,51 @@
+'use strict';
+
+constcommon=require('../common');
+
+if(!common.hasCrypto)
+common.skip('missing crypto');
+
+consthttps=require('https');
+consthttp=require('http');
+constnet=require('net');
+constassert=require('assert');
+consttls=require('tls');
+const{ readKey }=require('../common/fixtures');
+
+functionrequest(socket){
+socket.write('GET / HTTP/1.1\r\nConnection: keep-alive\r\n\r\n\r\n');
+}
+
+// https options
+consthttpsOptions={
+key: readKey('agent1-key.pem'),
+cert: readKey('agent1-cert.pem')
+};
+
+constserver=https.createServer(httpsOptions,common.mustCall((req,res)=>{
+res.end('ok');
+}));
+
+server.on('dropRequest',common.mustCall((request,socket)=>{
+assert.strictEqual(requestinstanceofhttp.IncomingMessage,true);
+assert.strictEqual(socketinstanceofnet.Socket,true);
+server.close();
+}));
+
+server.listen(0,common.mustCall(()=>{
+constsocket=tls.connect(
+server.address().port,
+{
+rejectUnauthorized: false
+},
+common.mustCall(()=>{
+request(socket);
+request(socket);
+socket.on('error',common.mustNotCall());
+socket.on('data',common.mustCallAtLeast());
+socket.on('close',common.mustCall());
+})
+);
+}));
+
+server.maxRequestsPerSocket=1;