I have been looking into some issues with TomEE using Websphere MQ, specifically issues where XA resources are returning a -7 error during a transaction commit when the system is under load. The -7 error indicates that the resource is closed.
The result of this error seems to be resources staying in the system somehow associated with the connection, and subsequently, these can't be enlisted in transactions (because they are closed).
The stacktrace is like this, and happens over and over again as the server attempts to process more messages from the queue.
WARN Transaction- Unable to enlist XAResource org.apache.geronimo.transaction.manager.WrapperNamedXAResource@3dd56e90, errorCode: -7
javax.transaction.xa.XAException: The method 'xa_start' has failed with errorCode '-7' due to the resource being closed.
at com.ibm.mq.jmqi.JmqiXAResource.start(JmqiXAResource.java:946) ~[com.ibm.mq.jmqi.jar:22.214.171.124 - p750-005-150424]
at com.ibm.mq.connector.xa.XARWrapper.start(XARWrapper.java:581) ~[com.ibm.mq.connector.jar:126.96.36.199-p750-005-150424]
at org.apache.geronimo.transaction.manager.WrapperNamedXAResource.start(WrapperNamedXAResource.java:111) ~[geronimo-transaction-3.1.4.jar:3.1.4]
at org.apache.geronimo.transaction.manager.TransactionImpl.enlistResource(TransactionImpl.java:209) [geronimo-transaction-3.1.4.jar:3.1.4]
at org.apache.geronimo.connector.outbound.TransactionEnlistingInterceptor.getConnection(TransactionEnlistingInterceptor.java:60) [geronimo-connector-3.1.4.jar:3.1.4]
at org.apache.geronimo.connector.outbound.TransactionCachingInterceptor.getConnection(TransactionCachingInterceptor.java:101) [geronimo-connector-3.1.4.jar:3.1.4]
at org.apache.geronimo.connector.outbound.ConnectionHandleInterceptor.getConnection(ConnectionHandleInterceptor.java:43) [geronimo-connector-3.1.4.jar:3.1.4]
at org.apache.geronimo.connector.outbound.TCCLInterceptor.getConnection(TCCLInterceptor.java:39) [geronimo-connector-3.1.4.jar:3.1.4]
at org.apache.geronimo.connector.outbound.ConnectionTrackingInterceptor.getConnection(ConnectionTrackingInterceptor.java:66) [geronimo-connector-3.1.4.jar:3.1.4]
at org.apache.geronimo.connector.outbound.AbstractConnectionManager.allocateConnection(AbstractConnectionManager.java:81) [geronimo-connector-3.1.4.jar:3.1.4]
at com.ibm.mq.connector.outbound.ConnectionFactoryImpl.createManagedJMSConnection(ConnectionFactoryImpl.java:194) [com.ibm.mq.connector.jar:188.8.131.52-p750-005-150424]
at com.ibm.mq.connector.outbound.ConnectionFactoryImpl.createConnectionInternal(ConnectionFactoryImpl.java:153) [com.ibm.mq.connector.jar:184.108.40.206-p750-005-150424]
at com.ibm.mq.connector.outbound.ConnectionFactoryImpl.createConnection(ConnectionFactoryImpl.java:138) [com.ibm.mq.connector.jar:220.127.116.11-p750-005-150424]
at com.ibm.mq.connector.outbound.ConnectionFactoryImpl.createConnection(ConnectionFactoryImpl.java:123) [com.ibm.mq.connector.jar:18.104.22.168-p750-005-150424]
The issue itself bears some resemblance to these posts:
com.ibm.mq.jmqi.JmqiXAResource has a isClosed field, and this is set when close_internal() is called. I tracked this call using AspectJ, and it appeared to happen here:
The interesting part here is the org.apache.openejb.resource.AutoConnectionTracker.setEnvironment() call, which is destroying connections where the proxy for the connection no longer has any references. I.e. if you had some code that did this:
Connection conn = connectionFactory.createConnection(); // conn is actually a proxy to the connection
// do work
conn = null; // or conn is out of scope
note that conn.close() is not called. The reference count to the proxy is now zero, so it counts as abandoned, and the next call to createConnection() destroys the associated connection. However, if all this happens in a transacted method, the JmqiXAResource is still enlisted with the transaction. So when the transaction goes to commit, it fails, because the JmqiXAResource is closed. The resource is still associated with a ManagedConnectionInfo object through ManagedConnectionInfo.xares (WrapperNamedXAResource). xaResource (XARWrapper - part of the RAR).theXAR (JmqiXAResource - part of the RAR). The ManagedConnectionInfo object somehow comes back to the pool after the rollback, and gets used again, with the TransactionImpl.enlistResource() call failing as above.
I suspect that we're seeing this under load as GC will be taking place more often and calls to createConnection() will be happening more frequently.
The connection proxies themselves don't do much - only calls to finalize() and clone() are caught. I propose this patch to allow the proxies to be disabled (the current behaviour is still the default): https://github.com/apache/tomee/pull/174 and welcome feedback.
Running this specific case with proxies disabled has yielded positive results. I'll try and extend this and reproduce it in a test case as well. I'm wondering if AutoConnectionTracker's use of ReferenceQueue is thread safe. Do anyone have any thoughts on this?
I experienced that kind of "surprise" in recent jvm since gc is way more aggressive - cause lambda are way more memory consuming ;). This lead to this kind of issue where the GC happens before the object should actually be finalizable.
I suspect we need to rework the AutoConnectionTracker to take into account these new behaviors and actually take into consideration the lifecycle of the underlying connection.
Maybe I got it wrong but I see the ability to disable the proxying as a quickfix/workaround - which is ok - but it means we need to fix the source anyway as a long term solution. Am I understanding it right? If so we need to ensure to keep the reference until the connection is released at least and ensure it was not closed in the pool (kind of testOnXXX).
Also wonder if there is anything related to geronimo since you cc-ed it. IIRC this logic is only in TomEE, no?
side note: reference queue is supposed thread safe yes.
Le ven. 28 sept. 2018 à 15:49, Jonathan Gallimore <[hidden email]> a écrit :
I apologize, I CC'd Geronimo in case there was anything relevant on the Geronimo connector side. Happy to drop the CC if its not relevant.
Thanks for the quick response!
Off the top of my head, I wonder if we could keep a reference to the connection proxy in the transaction (if there is one), and remove the reference when the transaction is complete?
On Fri, Sep 28, 2018 at 2:57 PM Romain Manni-Bucau <[hidden email]> wrote:
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