OK after some more digging it looks like proxy target is sending RST, ACK. Anybody got any clue? Is this normal? What can we do about it? The communication is JBoss to JBoss and same version EAP 7.0. ________________________________ Från: Jocke Eriksson Skickat: den 13 september 2019 09:15 Till: undertow-dev(a)lists.jboss.org <undertow-dev(a)lists.jboss.org&gt; Ämne: java.io.IOException: Connection reset by peer Hi we are using jboss EAP in production as an API gateway and we have a problem with the communication to some of our servers. We can see this in our logs. 2019-09-13 08:57:31,337 +0200 DEBUG [io.undertow.client] (default-undertow I/O-21) Connection closed with IOException: java.io.IOException: Connection reset by peer at sun.nio.ch.FileDispatcherImpl.read0(Native Method) [rt.jar:1.8.0_222] at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:39) [rt.jar:1.8.0_222] at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223) [rt.jar:1.8.0_222] at sun.nio.ch.IOUtil.read(IOUtil.java:192) [rt.jar:1.8.0_222] at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:380) [rt.jar:1.8.0_222] at org.xnio.nio.NioSocketConduit.read(NioSocketConduit.java:289) [xnio-nio.jar:3.4.3.Final-redhat-1] at org.xnio.conduits.PushBackStreamSourceConduit.read(PushBackStreamSourceConduit.java:52) [xnio-api.jar:3.4.3.Final-redhat-1] at org.xnio.conduits.ConduitStreamSourceChannel.read(ConduitStreamSourceChannel.java:127) [xnio-api.jar:3.4.3.Final-redhat-1] at io.undertow.client.http.HttpClientConnection$ClientReadListener.handleEvent(HttpClientConnection.java:510) at io.undertow.client.http.HttpClientConnection$ClientReadListener.handleEvent(HttpClientConnection.java:473) at org.xnio.ChannelListeners.invokeChannelListener(ChannelListeners.java:92) [xnio-api.jar:3.4.3.Final-redhat-1] at org.xnio.conduits.ReadReadyHandler$ChannelListenerHandler.readReady(ReadReadyHandler.java:66) [xnio-api.jar:3.4.3.Final-redhat-1] at org.xnio.nio.NioSocketConduit.handleReady(NioSocketConduit.java:89) [xnio-nio.jar:3.4.3.Final-redhat-1] at org.xnio.nio.WorkerThread.run(WorkerThread.java:567) [xnio-nio.jar:3.4.3.Final-redhat-1] 2019-09-13 08:57:31,339 +0200 ERROR [io.undertow.proxy] (default-undertow I/O-21) UT005028: Proxy request to /*****/******* failed: java.io.IOException: UT001000: Connection closed at io.undertow.client.http.HttpClientConnection$ClientReadListener.handleEvent(HttpClientConnection.java:516) at io.undertow.client.http.HttpClientConnection$ClientReadListener.handleEvent(HttpClientConnection.java:473) at org.xnio.ChannelListeners.invokeChannelListener(ChannelListeners.java:92) [xnio-api.jar:3.4.3.Final-redhat-1] at org.xnio.conduits.ReadReadyHandler$ChannelListenerHandler.readReady(ReadReadyHandler.java:66) [xnio-api.jar:3.4.3.Final-redhat-1] at org.xnio.nio.NioSocketConduit.handleReady(NioSocketConduit.java:89) [xnio-nio.jar:3.4.3.Final-redhat-1] at org.xnio.nio.WorkerThread.run(WorkerThread.java:567) [xnio-nio.jar:3.4.3.Final-redhat-1] The client receives a HTTP 503 response, any advice on how we can solve this is very welcome. Also it looks like we are setting up a lot of new connections, I was thinking it would be kept alive a bit longer. 2019-09-13 08:57:46,696 +0200 DEBUG [io.undertow.client] (default-undertow I/O-11) Connection to ********************:8080 was closed by the target server 2019-09-13 08:57:47,019 +0200 DEBUG [io.undertow.client] (default-undertow I/O-17) Connection to ********************:8080 was closed by the target server 2019-09-13 08:57:47,117 +0200 DEBUG [io.undertow.client] (default-undertow I/O-7) Connection to ********************:8080 was closed by the target server 2019-09-13 08:57:47,427 +0200 DEBUG [io.undertow.client] (default-undertow I/O-9) Connection to ********************:8080 was closed by the target server 2019-09-13 08:57:47,552 +0200 DEBUG [io.undertow.client] (default-undertow I/O-9) Connection to ********************:8080 was closed by the target server 2019-09-13 08:57:47,552 +0200 DEBUG [io.undertow.client] (default-undertow I/O-6) Connection to ********************:8080 was closed by the target server 2019-09-13 08:57:47,634 +0200 DEBUG [io.undertow.client] (default-undertow I/O-28) Connection to ********************:8080 was closed by the target server 2019-09-13 08:57:48,200 +0200 DEBUG [io.undertow.client] (default-undertow I/O-9) Connection to ********************:8080 was closed by the target server 2019-09-13 08:57:48,205 +0200 DEBUG [io.undertow.client] (default-undertow I/O-15) Connection to ********************8080 was closed by the target server