EMA Java user dispatcher thread deadlock

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question

ahmire.kailer

3 ●3 ●5 ●5

EMA Java user dispatcher thread deadlock

I'm using ema-3.5.0.1.jar with user dispatch mode.

The application sometimes deadlocks when it starts up. The deadlock comes from dispatcher threads. How long would it take to fix it? Is there a workaround? Below is the thread dump of relevant threads

"dispatcher-0" - Thread t@56
   java.lang.Thread.State: WAITING
        at java.base@11/jdk.internal.misc.Unsafe.park(Native Method)
        - waiting to lock <79b42f53> (a java.util.concurrent.locks.ReentrantLock$NonfairSync) owned by "dispatcher-2" t@60
        at java.base@11/java.util.concurrent.locks.LockSupport.park(LockSupport.java:194)
        at java.base@11/java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:885)
        at java.base@11/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:917)
        at java.base@11/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1240)
        at java.base@11/java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:267)
        at app//com.thomsonreuters.upa.valueadd.reactor.Reactor.submitChannel(Reactor.java:1989)
        at app//com.thomsonreuters.upa.valueadd.reactor.WlStream.encodeIntoBufferAndWrite(WlStream.java:748)
        at app//com.thomsonreuters.upa.valueadd.reactor.WlStream.sendCloseMsg(WlStream.java:793)
        at app//com.thomsonreuters.upa.valueadd.reactor.WlStream.timeout(WlStream.java:305)
        at app//com.thomsonreuters.upa.valueadd.reactor.Watchlist.timeout(Watchlist.java:328)
        at app//com.thomsonreuters.upa.valueadd.reactor.Reactor.processWorkerEvent(Reactor.java:2681)
        at app//com.thomsonreuters.upa.valueadd.reactor.Reactor.dispatchChannel(Reactor.java:1972)
        at app//com.thomsonreuters.upa.valueadd.reactor.ReactorChannel.dispatch(ReactorChannel.java:559)
        at app//com.thomsonreuters.ema.access.OmmBaseImpl.rsslReactorDispatchLoop(OmmBaseImpl.java:1336)
        at app//com.thomsonreuters.ema.access.OmmBaseImpl.dispatch(OmmBaseImpl.java:598)
        at app//com.thomsonreuters.ema.access.OmmConsumerImpl.dispatch(OmmConsumerImpl.java:185)
        at app//...
        at java.base@11/java.lang.Thread.run(Thread.java:834)

   Locked ownable synchronizers:
        - locked <1e9a6ed3> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

        - locked <60869d82> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

        - locked <9440f7d> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

"dispatcher-2" - Thread t@60
   java.lang.Thread.State: WAITING
        at java.base@11/jdk.internal.misc.Unsafe.park(Native Method)
        - waiting to lock <1e9a6ed3> (a java.util.concurrent.locks.ReentrantLock$NonfairSync) owned by "dispatcher-0" t@56
        at java.base@11/java.util.concurrent.locks.LockSupport.park(LockSupport.java:194)
        at java.base@11/java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:885)
        at java.base@11/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:917)
        at java.base@11/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1240)
        at java.base@11/java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:267)
        at app//com.thomsonreuters.upa.valueadd.reactor.Reactor.submitChannel(Reactor.java:1989)
        at app//com.thomsonreuters.upa.valueadd.reactor.WlStream.encodeIntoBufferAndWrite(WlStream.java:748)
        at app//com.thomsonreuters.upa.valueadd.reactor.WlStream.sendCloseMsg(WlStream.java:793)
        at app//com.thomsonreuters.upa.valueadd.reactor.WlStream.timeout(WlStream.java:305)
        at app//com.thomsonreuters.upa.valueadd.reactor.Watchlist.timeout(Watchlist.java:328)
        at app//com.thomsonreuters.upa.valueadd.reactor.Reactor.processWorkerEvent(Reactor.java:2681)
        at app//com.thomsonreuters.upa.valueadd.reactor.Reactor.dispatchChannel(Reactor.java:1972)
        at app//com.thomsonreuters.upa.valueadd.reactor.ReactorChannel.dispatch(ReactorChannel.java:559)
        at app//com.thomsonreuters.ema.access.OmmBaseImpl.rsslReactorDispatchLoop(OmmBaseImpl.java:1336)
        at app//com.thomsonreuters.ema.access.OmmBaseImpl.dispatch(OmmBaseImpl.java:598)
        at app//com.thomsonreuters.ema.access.OmmConsumerImpl.dispatch(OmmConsumerImpl.java:185)
        at app//...
        at java.base@11/java.lang.Thread.run(Thread.java:834)

   Locked ownable synchronizers:
        - locked <79b42f53> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

        - locked <75883433> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

        - locked <6da685c> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

elektron refinitiv-realtime elektron-sdk rrt ema-api elektron-message-api java

Jul 24, 2020 at 06:02 PM

10 |1500

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nick.zincone Jul 24, 2020 at 08:52 PM

Hi @ahmire.kailer,

Can you please point us to which EMA sample is causing this issue so the development team can confirm it is an issue within the library? Thanks.

ahmire.kailer nick.zincone Jul 27, 2020 at 09:27 AM

Hi @nick.zincone.1

The code is similar to example130 and example410 combined.

In summary:

User dispatch mode
Multiple consumers with the same user name
Multiple threads calling OmmConsumer.registerClient() (registerClient is never invoked by dispatcher threads, dispatcher threads only decode)
Long dispatch timeout - OmmConsumer.dispatch(Long.MAX_VALUE) (not sure if this is the best way to wait indefinitely for data, it not please advise)

wasin.w Nov 17, 2020 at 02:50 AM

Hello @ahmire.kailer

I found that you have summitted this issue as issue #151 on GitHub. Did you have a chance to test the work around that suggested by the Dev team?

Answer 1 · 2020-07-27T12:40:17Z

nick.zincone

13.8k ●61 ●39 ●63

Hi @ahmire.kailer,

In order for the development team to fix a problem within the library, they will need to reproduce the error. Because this isn't a specific example they released that is causing an issue, but instead a hybrid example you put together, you will need to provide the example for them to replicate and show it is an issue within the library, not your application. Ideally, if you can narrow down your example to a minimal code segment, this will allow them to determine where the issue is.

The EMA Project has an issue section that will allow you to report your finding within the library within GitHub.

Jul 27, 2020 at 12:40 PM

10 |1500

Attachments: Up to 2 attachments (including images) can be used with a maximum of 512.0 KiB each and 1.0 MiB total.

Answer 2 · 2020-07-29T16:00:55Z

ahmire.kailer

3 ●3 ●5 ●5

Hi @nick.zincone.1

I tried to reproduce the problem using much simplified code without success. I then downgraded back to ema-3.4.0.1.jar , it hasn't deadlocked so far. I had deadlock problems with 3.4 using API dispatch, there're suggestions that deadlock could be avoided by using user dispatch and it indeed worked. I upgraded to 3.5 last week thinking it would be better. I'll use 3.4 for now. If I manage to come up with a simple example that could reproduce the problem, I'll put it here.

Jul 29, 2020 at 04:00 PM

10 |1500

Attachments: Up to 2 attachments (including images) can be used with a maximum of 512.0 KiB each and 1.0 MiB total.

Answer 3 · 2020-08-17T04:30:26Z

wasin.w

17.5k ●35 ●12 ●12

The issue has been submitted as part of issue #149 on GitHub.

Aug 17, 2020 at 04:30 AM

10 |1500

Attachments: Up to 2 attachments (including images) can be used with a maximum of 512.0 KiB each and 1.0 MiB total.

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