Hello Mr. Robin Shen,
Could you please add connection retry method every time HessianProxy connection has exception?
We want QB will retry until the AgentConnectivityTask is maintaining connection if there is an exception on connection.

Here are the logs:
Step 'master>Build_Steps' is failed.
    java.lang.RuntimeException: Error executing step process job.
        at com.pmease.quickbuild.stepsupport.StepProcessTask.reduce(StepProcessTask.java:126)
        at com.pmease.quickbuild.stepsupport.StepProcessTask.reduce(StepProcessTask.java:19)
        at com.pmease.quickbuild.grid.GridTaskFuture.get(GridTaskFuture.java:168)
        at com.pmease.quickbuild.grid.GridTaskFuture.get(GridTaskFuture.java:172)
        at com.pmease.quickbuild.stepsupport.SequentialStep.triggerChildren(SequentialStep.java:46)
        at com.pmease.quickbuild.stepsupport.CompositeStep.run(CompositeStep.java:133)
        at com.pmease.quickbuild.stepsupport.Step.doExecute(Step.java:661)
        at com.pmease.quickbuild.stepsupport.Step.execute(Step.java:575)
        at com.pmease.quickbuild.stepsupport.StepExecutionJob.executeStepAwareJob(StepExecutionJob.java:31)
        at com.pmease.quickbuild.stepsupport.StepAwareJob.executeBuildAwareJob(StepAwareJob.java:56)
        at com.pmease.quickbuild.BuildAwareJob.execute(BuildAwareJob.java:79)
        at com.pmease.quickbuild.grid.GridJob.run(GridJob.java:131)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:750)
    Caused by: java.lang.RuntimeException: Error executing step execution job.
        at com.pmease.quickbuild.stepsupport.StepExecutionTask.reduce(StepExecutionTask.java:29)
        at com.pmease.quickbuild.stepsupport.StepExecutionTask.reduce(StepExecutionTask.java:19)
        at com.pmease.quickbuild.grid.GridTaskFuture.get(GridTaskFuture.java:168)
        at com.pmease.quickbuild.grid.GridTaskFuture.get(GridTaskFuture.java:172)
        at com.pmease.quickbuild.stepsupport.StepProcessJob.executeStepAwareJob(StepProcessJob.java:46)
        ... 8 more
    Caused by: com.caucho.hessian.client.HessianRuntimeException: com.caucho.hessian.client.HessianRuntimeException: Error connecting 'http://QB_ip/service/server'
        at com.caucho.hessian.client.HessianProxy.sendRequest(HessianProxy.java:285)
        at com.caucho.hessian.client.HessianProxy.invoke(HessianProxy.java:171)
        at com.sun.proxy.$Proxy35.stepUpdated(Unknown Source)
        at com.pmease.quickbuild.stepsupport.StepExecutionJob.executeStepAwareJob(StepExecutionJob.java:57)
        ... 8 more
    Caused by: com.caucho.hessian.client.HessianRuntimeException: Error connecting 'http://QB_ip/service/server'
        at com.caucho.hessian.client.HessianURLConnection.getOutputStream(HessianURLConnection.java:103)
        at com.caucho.hessian.client.HessianProxy.sendRequest(HessianProxy.java:283)
        ... 11 more
    Caused by: java.net.SocketTimeoutException: connect timed out
        at java.net.PlainSocketImpl.socketConnect(Native Method)
        at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
        at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
        at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
        at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
        at java.net.Socket.connect(Socket.java:607)
        at sun.net.NetworkClient.doConnect(NetworkClient.java:175)
        at sun.net.www.http.HttpClient.openServer(HttpClient.java:463)
        at sun.net.www.http.HttpClient.openServer(HttpClient.java:558)
        at sun.net.www.http.HttpClient.<init>(HttpClient.java:242)
        at sun.net.www.http.HttpClient.New(HttpClient.java:339)
        at sun.net.www.http.HttpClient.New(HttpClient.java:357)
        at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1228)
        at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1162)
        at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1056)
        at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:990)
        at sun.net.www.protocol.http.HttpURLConnection.getOutputStream0(HttpURLConnection.java:1342)
        at sun.net.www.protocol.http.HttpURLConnection.getOutputStream(HttpURLConnection.java:1317)
        at com.caucho.hessian.client.HessianURLConnection.getOutputStream(HessianURLConnection.java:99)
        ... 12 more