sporadic response problems

[MichaelRoeder]

In rare cases, the annotation systems do not respond and an exception like the following is thrown (IP address has been replaced):

GerbilException: Exception while sending request. (error type -106: Got an unexpected exception while running the experiment.)
        at org.aksw.gerbil.http.AbstractHttpRequestEmitter.sendRequest(AbstractHttpRequestEmitter.java:163)
        at org.aksw.gerbil.annotator.impl.nif.NIFBasedAnnotatorWebservice.request(NIFBasedAnnotatorWebservice.java:137)
        at org.aksw.gerbil.annotator.impl.nif.NIFBasedAnnotatorWebservice.performAnnotation(NIFBasedAnnotatorWebservice.java:109)
        at org.aksw.gerbil.annotator.impl.nif.NIFBasedAnnotatorWebservice.performA2KBTask(NIFBasedAnnotatorWebservice.java:89)
        at org.aksw.gerbil.annotator.decorator.TimeMeasuringAnnotatorDecorator.performExtraction(TimeMeasuringAnnotatorDecorator.java:211)
        at org.aksw.gerbil.annotator.decorator.TimeMeasuringAnnotatorDecorator$TimeMeasuringA2KBAnnotator.performA2KBTask(TimeMeasuringAnnotatorDecorator.java:141)
        at org.aksw.gerbil.annotator.decorator.ErrorCountingAnnotatorDecorator.performExtraction(ErrorCountingAnnotatorDecorator.java:276)
        at org.aksw.gerbil.annotator.decorator.ErrorCountingAnnotatorDecorator$ErrorCountingA2KBAnnotator.performA2KBTask(ErrorCountingAnnotatorDecorator.java:159)
        at org.aksw.gerbil.annotator.decorator.SingleInstanceSecuringAnnotatorDecorator.performExtraction(SingleInstanceSecuringAnnotatorDecorator.java:243)
        at org.aksw.gerbil.annotator.decorator.SingleInstanceSecuringAnnotatorDecorator$SingleInstanceSecuringA2KBAnnotator.performA2KBTask(SingleInstanceSecuringAnnotatorDecorator.java:147)
        at org.aksw.gerbil.execute.ExperimentTask.runExperiment(ExperimentTask.java:341)
        at org.aksw.gerbil.execute.ExperimentTask.run(ExperimentTask.java:135)
        at org.aksw.simba.topicmodeling.concurrent.workers.WorkerImpl.run(WorkerImpl.java:44)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.http.NoHttpResponseException: A.B.C.D:E failed to respond
        at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:143)
        at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:57)
        at org.apache.http.impl.io.AbstractMessageParser.parse(AbstractMessageParser.java:261)
        at org.apache.http.impl.DefaultBHttpClientConnection.receiveResponseHeader(DefaultBHttpClientConnection.java:165)
        at org.apache.http.impl.conn.CPoolProxy.receiveResponseHeader(CPoolProxy.java:167)
        at org.apache.http.protocol.HttpRequestExecutor.doReceiveResponse(HttpRequestExecutor.java:272)
        at org.apache.http.protocol.HttpRequestExecutor.execute(HttpRequestExecutor.java:124)
        at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:271)
        at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:184)
        at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:88)
        at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
        at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:184)
        at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82)
        at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:107)
        at org.aksw.gerbil.http.AbstractHttpRequestEmitter.sendRequest(AbstractHttpRequestEmitter.java:146)
        ... 15 more

However, the annotation system is responding if the same experiment is run again. Using the correct retry strategy should avoid this kind of error.