When the plugin is sending 'queue' requests to Logstash, we are seeing the following messages in the Jenkins log:
The request for url http://logstashserver:5000/jenkins_queue/ has failed.
org.apache.http.ConnectionClosedException: Connection closed
Caused: com.mashape.unirest.http.exceptions.UnirestException
at com.mashape.unirest.http.HttpClientHelper$1.failed(HttpClientHelper.java:86)
at org.apache.http.concurrent.BasicFuture.failed(BasicFuture.java:134)
at org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl.failed(DefaultClientExchangeHandlerImpl.java:258)
at org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl.connectionAllocated(DefaultClientExchangeHandlerImpl.java:305)
at org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl.access$000(DefaultClientExchangeHandlerImpl.java:63)
at org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl$1.completed(DefaultClientExchangeHandlerImpl.java:360)
at org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl$1.completed(DefaultClientExchangeHandlerImpl.java:357)
at org.apache.http.concurrent.BasicFuture.completed(BasicFuture.java:119)
at org.apache.http.impl.nio.conn.PoolingNHttpClientConnectionManager$InternalPoolEntryCallback.completed(PoolingNHttpClientConnectionManager.java:465)
at org.apache.http.impl.nio.conn.PoolingNHttpClientConnectionManager$InternalPoolEntryCallback.completed(PoolingNHttpClientConnectionManager.java:449)
at org.apache.http.concurrent.BasicFuture.completed(BasicFuture.java:119)
at org.apache.http.nio.pool.AbstractNIOConnPool.fireCallbacks(AbstractNIOConnPool.java:443)
at org.apache.http.nio.pool.AbstractNIOConnPool.lease(AbstractNIOConnPool.java:276)
at org.apache.http.impl.nio.conn.PoolingNHttpClientConnectionManager.requestConnection(PoolingNHttpClientConnectionManager.java:261)
at org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl.requestConnection(DefaultClientExchangeHandlerImpl.java:351)
at org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl.start(DefaultClientExchangeHandlerImpl.java:126)
at org.apache.http.impl.nio.client.InternalHttpAsyncClient.execute(InternalHttpAsyncClient.java:129)
at org.apache.http.impl.nio.client.CloseableHttpAsyncClient.execute(CloseableHttpAsyncClient.java:72)
at org.apache.http.impl.nio.client.CloseableHttpAsyncClient.execute(CloseableHttpAsyncClient.java:102)
at org.apache.http.impl.nio.client.CloseableHttpAsyncClient.execute(CloseableHttpAsyncClient.java:87)
at com.mashape.unirest.http.HttpClientHelper.requestAsync(HttpClientHelper.java:102)
at com.mashape.unirest.request.BaseRequest.asJsonAsync(BaseRequest.java:76)
at org.jenkins.plugins.statistics.gatherer.util.RestClientUtil.postToService(RestClientUtil.java:32)
at org.jenkins.plugins.statistics.gatherer.listeners.QueueStatsListener.onLeft(QueueStatsListener.java:222)
at hudson.model.Queue$LeftItem.enter(Queue.java:2777)
at hudson.model.Queue.onStartExecuting(Queue.java:1163)
at hudson.model.Executor$1.call(Executor.java:361)
at hudson.model.Executor$1.call(Executor.java:347)
at hudson.model.Queue._withLock(Queue.java:1440)
at hudson.model.Queue.withLock(Queue.java:1301)
at hudson.model.Executor.run(Executor.java:347)