03 April 2021
Wildfly provides great out of the box load balancing support by Undertow and modcluster subsystems
Unfortunately, in case HTTP headers size is huge enough (close to 16K), which is so actual in JWT era - pity error happened:
ERROR [io.undertow.proxy] (default I/O-10) UT005028: Proxy request to /ee-jax-rs-examples/clusterdemo/serverinfo failed: java.io.IOException: java.nio.BufferOverflowException
at io.undertow.server.handlers.proxy.ProxyHandler$HTTPTrailerChannelListener.handleEvent(ProxyHandler.java:771)
at io.undertow.server.handlers.proxy.ProxyHandler$ProxyAction$1.completed(ProxyHandler.java:646)
at io.undertow.server.handlers.proxy.ProxyHandler$ProxyAction$1.completed(ProxyHandler.java:561)
at io.undertow.client.ajp.AjpClientExchange.invokeReadReadyCallback(AjpClientExchange.java:203)
at io.undertow.client.ajp.AjpClientConnection.initiateRequest(AjpClientConnection.java:288)
at io.undertow.client.ajp.AjpClientConnection.sendRequest(AjpClientConnection.java:242)
at io.undertow.server.handlers.proxy.ProxyHandler$ProxyAction.run(ProxyHandler.java:561)
at io.undertow.util.SameThreadExecutor.execute(SameThreadExecutor.java:35)
at io.undertow.server.HttpServerExchange.dispatch(HttpServerExchange.java:815)
...
Caused by: java.nio.BufferOverflowException
at java.nio.Buffer.nextPutIndex(Buffer.java:521)
at java.nio.DirectByteBuffer.put(DirectByteBuffer.java:297)
at io.undertow.protocols.ajp.AjpUtils.putString(AjpUtils.java:52)
at io.undertow.protocols.ajp.AjpClientRequestClientStreamSinkChannel.createFrameHeaderImpl(AjpClientRequestClientStreamSinkChannel.java:176)
at io.undertow.protocols.ajp.AjpClientRequestClientStreamSinkChannel.generateSendFrameHeader(AjpClientRequestClientStreamSinkChannel.java:290)
at io.undertow.protocols.ajp.AjpClientFramePriority.insertFrame(AjpClientFramePriority.java:39)
at io.undertow.protocols.ajp.AjpClientFramePriority.insertFrame(AjpClientFramePriority.java:32)
at io.undertow.server.protocol.framed.AbstractFramedChannel.flushSenders(AbstractFramedChannel.java:603)
at io.undertow.server.protocol.framed.AbstractFramedChannel.flush(AbstractFramedChannel.java:742)
at io.undertow.server.protocol.framed.AbstractFramedChannel.queueFrame(AbstractFramedChannel.java:735)
at io.undertow.server.protocol.framed.AbstractFramedStreamSinkChannel.queueFinalFrame(AbstractFramedStreamSinkChannel.java:267)
at io.undertow.server.protocol.framed.AbstractFramedStreamSinkChannel.shutdownWrites(AbstractFramedStreamSinkChannel.java:244)
at io.undertow.channels.DetachableStreamSinkChannel.shutdownWrites(DetachableStreamSinkChannel.java:79)
at io.undertow.server.handlers.proxy.ProxyHandler$HTTPTrailerChannelListener.handleEvent(ProxyHandler.java:754)
The same request directly to backend server works well. Tried to play with ajp-listener and mod-cluster filter "max-*" parameters, but have no luck.
Possible solution here is switch protocol from AJP to HTTP which can be bit less effective, but works well with big headers:
/profile=full-ha/subsystem=modcluster/proxy=default:write-attribute(name=listener, value=default)