ConnectionLimit doesn't work with WebSocket connections. #13324
Description
Jetty version(s)
The issue is reproduced for Jetty 12.0.20. It was most likely introduced by change: https://github.com/jetty/jetty.project/pull/12320/files where Set of accepting connections was replaced by simple counter.
Jetty Environment
Any
Java version/vendor (use: java -version)
Any
OS type/version
Any
Description
org.eclipse.jetty.server.ConnectionLimit is created to limit active connections that Jetty server is handling. However, internal logic of this class doesn't work properly for web socket connections.
The problem is with _accepting counter: it is decremented for each onOpened call. In web socket case, onOpened called twice: for handshake and actual WS connection. So _accepting counter enters negative values and the behavior of limiter is broken. Logs:
14:25:16.140 [qtp1782580546-35-acceptor-0@3ca674fe-ServerConnector@740fb309{HTTP/1.1, (http/1.1)}{0.0.0.0:8080}] DEBUG o.e.jetty.server.ConnectionLimit - Accepting (1+0) <= 5 java.nio.channels.SocketChannel[connected local=/[0:0:0:0:0:0:0:1]:8080 remote=/[0:0:0:0:0:0:0:1]:63507]
14:25:16.175 [qtp1782580546-36] DEBUG o.e.jetty.server.ConnectionLimit - Opened (0+1) <= 5 HttpConnection@4b126155::SocketChannelEndPoint@2c168a4[{l=/[0:0:0:0:0:0:0:1]:8080,r=/[0:0:0:0:0:0:0:1]:63507,OPEN,fill=-,flush=-,to=29/30000}{io=0/0,kio=0,kro=0}]->[HttpConnection@4b126155[p=HttpParser{s=START,0 of -1},g=HttpGenerator@2771ee38{s=START}]=>HttpChannelState@63c5b38f{handling=null, handled=false, send=SENDING, completed=false, request=null}]
14:25:16.222 [qtp1782580546-38] DEBUG o.e.jetty.server.ConnectionLimit - Closed (0+0) <= 5 HttpConnection@4b126155::SocketChannelEndPoint@2c168a4[{l=/[0:0:0:0:0:0:0:1]:8080,r=/[0:0:0:0:0:0:0:1]:63507,OPEN,fill=-,flush=-,to=1/30000}{io=0/0,kio=0,kro=1}]->[HttpConnection@4b126155[p=HttpParser{s=END,0 of -1},g=HttpGenerator@2771ee38{s=END}]=>HttpChannelState@63c5b38f{handling=null, handled=true, send=LAST_COMPLETE, completed=true, request=GET@2a4a534a http://localhost:8080/echo HTTP/1.1}]
14:25:16.222 [qtp1782580546-38] DEBUG o.e.jetty.server.ConnectionLimit - Opened (-1+1) <= 5 WebSocketConnection@3c760760::SocketChannelEndPoint@2c168a4[{l=/[0:0:0:0:0:0:0:1]:8080,r=/[0:0:0:0:0:0:0:1]:63507,OPEN,fill=-,flush=-,to=2/30000}{io=0/0,kio=0,kro=1}]->[WebSocketConnection@3c760760[SERVER,p=Parser@199c38ac[s=START,c=0,o=0x0,m=-,l=0],f=Flusher@6958aafa[IDLE][queueSize=0,aggregate=null],g=org.eclipse.jetty.websocket.core.internal.Generator@11706498]]
14:26:16.279 [qtp1782580546-21] DEBUG o.e.jetty.server.ConnectionLimit - Closed (-1+0) <= 5 WebSocketConnection@3c760760::SocketChannelEndPoint@2c168a4[{l=null,r=null,CLOSED,fill=-,flush=-,to=2/30000}{io=0/0,kio=-1,kro=-1}]->[WebSocketConnection@3c760760[SERVER,p=Parser@199c38ac[s=START,c=0,o=0x0,m=-,l=0],f=Flusher@6958aafa[FAILED][queueSize=0,aggregate=null],g=org.eclipse.jetty.websocket.core.internal.Generator@11706498]]
How to reproduce?
Demo repo
Run application with main class org.example.websocketdemo.EchoServer. It has connection limit configured to 5.
Run python script in root folder. It will successfully open 20 connections.