I had a build in our buildserver, that hung for 2 hours that usually needs only 10 minutes. It seems to be Gradle who caused this. Following you have the relevant excerpt of the output. The last line was after cancelling the build. Gradle Version in use is 1.0.
[12:34:53][:subproject:test] Could not dispatch message [ProducerUnavailable id: 7f2fc405-3ec3-4d85-ad1d-b846803d5d24]. Discarding message.
[12:34:53][:subproject:test] java.lang.IllegalStateException: Cannot dispatch message, as this message dispatch has been stopped. Message: incoming [ProducerUnavailable id: 7f2fc405-3ec3-4d85-ad1d-b846803d5d24]
[12:34:53][:subproject:test] at org.gradle.messaging.dispatch.AsyncDispatch.dispatch(AsyncDispatch.java:147)
[12:34:53][:subproject:test] at org.gradle.messaging.remote.internal.ProtocolStack$BottomConnection.dispatch(ProtocolStack.java:292)
[12:34:53][:subproject:test] at org.gradle.messaging.dispatch.QueuingDispatch.dispatch(QueuingDispatch.java:59)
[12:34:53][:subproject:test] at org.gradle.messaging.remote.internal.Router$Endpoint.dispatchIncoming(Router.java:124)
[12:34:53][:subproject:test] at org.gradle.messaging.remote.internal.Router$RemoteGroup.removeRoute(Router.java:232)
[12:34:53][:subproject:test] at org.gradle.messaging.remote.internal.Router$Endpoint$2.run(Router.java:100)
[12:34:53][:subproject:test] at org.gradle.messaging.remote.internal.Router$1.dispatch(Router.java:50)
[12:34:53][:subproject:test] at org.gradle.messaging.remote.internal.Router$1.dispatch(Router.java:48)
[12:34:53][:subproject:test] at org.gradle.messaging.dispatch.AsyncDispatch.dispatchMessages(AsyncDispatch.java:132)
[12:34:53][:subproject:test] at org.gradle.messaging.dispatch.AsyncDispatch.access$000(AsyncDispatch.java:33)
[12:34:53][:subproject:test] at org.gradle.messaging.dispatch.AsyncDispatch$1.run(AsyncDispatch.java:72)
[12:34:53][:subproject:test] at org.gradle.messaging.concurrent.DefaultExecutorFactory$StoppableExecutorImpl$1.run(DefaultExecutorFactory.java:66)
[12:34:53][:subproject:test] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
[12:34:53][:subproject:test] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
[12:34:53][:subproject:test] at java.lang.Thread.run(Thread.java:722)
[12:34:53][:subproject:test] Could not dispatch message [EndOfStreamEvent]. Discarding message.
[12:34:53][:subproject:test] java.lang.NullPointerException
[12:34:53][:subproject:test] at org.gradle.messaging.remote.internal.Router$RemoteGroup.removeRoute(Router.java:230)
[12:34:53][:subproject:test] at org.gradle.messaging.remote.internal.Router$Endpoint$2.run(Router.java:108)
[12:34:53][:subproject:test] at org.gradle.messaging.remote.internal.Router$1.dispatch(Router.java:50)
[12:34:53][:subproject:test] at org.gradle.messaging.remote.internal.Router$1.dispatch(Router.java:48)
[12:34:53][:subproject:test] at org.gradle.messaging.dispatch.AsyncDispatch.dispatchMessages(AsyncDispatch.java:132)
[12:34:53][:subproject:test] at org.gradle.messaging.dispatch.AsyncDispatch.access$000(AsyncDispatch.java:33)
[12:34:53][:subproject:test] at org.gradle.messaging.dispatch.AsyncDispatch$1.run(AsyncDispatch.java:72)
[12:34:53][:subproject:test] at org.gradle.messaging.concurrent.DefaultExecutorFactory$StoppableExecutorImpl$1.run(DefaultExecutorFactory.java:66)
[12:34:53][:subproject:test] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
[12:34:53][:subproject:test] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
[12:34:53][:subproject:test] at java.lang.Thread.run(Thread.java:722)
[14:45:16]Process exited with code 137
