Lock timeout exception upon reading of entries from the clustered cache

Issue

We are using mod_jk in front of a Cluster of JBoss Enterprise Application Servers. Sometimes we find lock timeout exception upon reading of entries from the cache:

An exception or error occurred in the container during the request processing: java.lang.RuntimeException: JBAS018060: Exception acquiring ownership of XXX

    at org.jboss.as.web.session.ClusteredSession.access(ClusteredSession.java:503)

    at org.apache.catalina.connector.Request.doGetSession(Request.java:2625)

    at org.apache.catalina.connector.Request.getSession(Request.java:2375)

    at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:99)

    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155)

    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)

    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:567)

    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)

    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:372)

    at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:505)

    at org.apache.coyote.ajp.AjpProtocol$AjpConnectionHandler.process(AjpProtocol.java:453)

    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:931)

    at java.lang.Thread.run(Thread.java:745)

Caused by: org.jboss.as.clustering.lock.TimeoutException: JBAS010213: Cannot acquire lock default-host/authentication/XXX from cluster

    at org.jboss.as.clustering.lock.SharedLocalYieldingClusterLockManager.lock(SharedLocalYieldingClusterLockManager.java:439)

    at org.jboss.as.clustering.web.infinispan.DistributedCacheManager.acquireSessionOwnership(DistributedCacheManager.java:381)

    at org.jboss.as.web.session.ClusteredSession.acquireSessionOwnership(ClusteredSession.java:529)

    at org.jboss.as.web.session.ClusteredSession.access(ClusteredSession.java:501)

    ... 12 more

Without action, once error occurred once, it degraded up to having timeouts over most access to the distributed cache.