我在WSO2 ESB 4.9.0上运行了一个生产环境。我面临一个奇怪的错误。此类型错误在每10秒或15秒后随机出现在不同的组件上。
错误消息1：
Unexpected error sending message back
at org.apache.synapse.core.axis2.Axis2Sender.handleException(Axis2Sender.java:247)
at org.apache.synapse.core.axis2.Axis2Sender.sendBack(Axis2Sender.java:215)
at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.send(Axis2SynapseEnvironment.java:444)
at org.apache.synapse.mediators.builtin.SendMediator.mediate(SendMediator.java:102)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:81)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:48)
at org.apache.synapse.config.xml.AnonymousListMediator.mediate(AnonymousListMediator.java:30)
at org.apache.synapse.config.xml.SwitchCase.mediate(SwitchCase.java:66)
at org.apache.synapse.mediators.filters.SwitchMediator.mediate(SwitchMediator.java:123)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:81)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:48)
at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:149)
at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage(Axis2SynapseEnvironment.java:297)
at org.apache.synapse.core.axis2.SynapseCallbackReceiver.handleMessage(SynapseCallbackReceiver.java:529)
at org.apache.synapse.core.axis2.SynapseCallbackReceiver.receive(SynapseCallbackReceiver.java:172)
at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
at org.apache.synapse.transport.passthru.ClientWorker.run(ClientWorker.java:247)
at org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.axis2.AxisFault: Failed to submit the response
at org.apache.synapse.transport.passthru.PassThroughHttpSender.handleException(PassThroughHttpSender.java:610)
at org.apache.synapse.transport.passthru.PassThroughHttpSender.invoke(PassThroughHttpSender.java:269)
at org.apache.axis2.engine.AxisEngine.send(AxisEngine.java:442)
at org.apache.synapse.core.axis2.Axis2Sender.sendBack(Axis2Sender.java:212)
... 19 more
Caused by: java.lang.NullPointerException
错误消息2：
Unexpected error sending message back {org.apache.synapse.core.axis2.Axis2Sender}
org.apache.axis2.AxisFault: Failed to submit the response
at org.apache.synapse.transport.passthru.PassThroughHttpSender.handleException(PassThroughHttpSender.java:610)
at org.apache.synapse.transport.passthru.PassThroughHttpSender.invoke(PassThroughHttpSender.java:269)
at org.apache.axis2.engine.AxisEngine.send(AxisEngine.java:442)
at org.apache.synapse.core.axis2.Axis2Sender.sendBack(Axis2Sender.java:212)
at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.send(Axis2SynapseEnvironment.java:444)
at org.apache.synapse.mediators.builtin.SendMediator.mediate(SendMediator.java:102)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:81)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:48)
at org.apache.synapse.config.xml.AnonymousListMediator.mediate(AnonymousListMediator.java:30)
at org.apache.synapse.config.xml.SwitchCase.mediate(SwitchCase.java:66)
at org.apache.synapse.mediators.filters.SwitchMediator.mediate(SwitchMediator.java:123)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:81)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:48)
at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:149)
at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage(Axis2SynapseEnvironment.java:297)
at org.apache.synapse.core.axis2.SynapseCallbackReceiver.handleMessage(SynapseCallbackReceiver.java:529)
at org.apache.synapse.core.axis2.SynapseCallbackReceiver.receive(SynapseCallbackReceiver.java:172)
at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
at org.apache.synapse.transport.passthru.ClientWorker.run(ClientWorker.java:247)
at org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
问题：
主要问题是实际上正在发送所有消息并在后端接收响应。我已经对所有各方进行了双重检查，包括消费和生产方面。没有消息被删除。但在ESB日志中，这些消息经常出现。并且ESB是否有可能向我们提供错误消息，因为实际上消息是完全发送和接收的。如果是这样，为什么ESB认为没有发送回复？