Hi Team,

Recently we have upgraded our Pega platform from V7.2.2 to V8.4.1 and post upgrade, we are observing below exception in the logs. can you please help us to understand on which scenario this exception occurs and how can we resolve that?

[on-delegator-pool-13] [  STANDARD] [                    ] [                    ] (          mgmt.base.ThreadData) ERROR   - Trying to use a recycled thread com.pega.pegarules.pub.context.StaleThreadError: Thread has been recycled     at com.pega.pegarules.session.internal.mgmt.base.ThreadData.validateUse(ThreadData.java:840) ~[prprivate-session.jar:?]     at com.pega.pegarules.session.internal.mgmt.PRThreadImpl.validateUse(PRThreadImpl.java:193) ~[prprivate-session.jar:?]     at com.pega.pegarules.session.internal.mgmt.PRThreadImpl.getDatabase(PRThreadImpl.java:345) ~[prprivate-session.jar:?]     at com.pega.pegarules.data.internal.sqlapi.resolve.NativeSQLAPIResolver.resolveDBRelatedInfo(NativeSQLAPIResolver.java:1052) ~[prprivate-data.jar:?]     at com.pega.pegarules.data.internal.sqlapi.resolve.NativeSQLAPIResolver.resolve(NativeSQLAPIResolver.java:120) ~[prprivate-data.jar:?]     at com.pega.dsm.dnode.util.NativeSQLBatchReader.<init>(NativeSQLBatchReader.java:94) ~[d-node.jar:?]     at com.pega.dsm.dnode.util.NativeSQLBatchReader.<init>(NativeSQLBatchReader.java:98) ~[d-node.jar:?]     at com.pega.dsm.dnode.util.NativeSQLBatchReader.<init>(NativeSQLBatchReader.java:102) ~[d-node.jar:?]     at com.pega.dsm.dnode.impl.dataflow.service.persistence.db.PersistenceDbUtils$1.emit(PersistenceDbUtils.java:239) ~[d-node.jar:?]     at com.pega.dsm.dnode.impl.stream.DataObservableImpl$SafeDataSubscriber.subscribe(DataObservableImpl.java:353) ~[d-node.jar:?]     at com.pega.dsm.dnode.impl.stream.DataObservableImpl.subscribe(DataObservableImpl.java:55) ~[d-node.jar:?]     at com.pega.dsm.dnode.impl.stream.DataObservableImpl.await(DataObservableImpl.java:117) ~[d-node.jar:?]     at com.pega.dsm.dnode.impl.stream.DataObservableImpl.await(DataObservableImpl.java:106) ~[d-node.jar:?]     at com.pega.dsm.dnode.impl.dataflow.asyncexecutor.QueueProcessorDataSetOperationsImpl.getLag(QueueProcessorDataSetOperationsImpl.java:307) ~[d-node.jar:?]     at com.pega.platform.executor.queueprocessor.internal.QueueProcessorManagementOperationsImpl$LagCalculator.execute(QueueProcessorManagementOperationsImpl.java:323) ~[pega-executor.jar:?]     at com.pega.platform.executor.queueprocessor.internal.BatchTask.lambda$executeInBorrowedRequestor$0(BatchTask.java:80) ~[pega-executor.jar:?]     at com.pega.platform.executor.queueprocessor.internal.BatchTask$$Lambda$2091.0000000020DCAFC0.run(Unknown Source) ~[?:?]     at com.pega.pegarules.session.internal.PRSessionProviderImpl.performTargetActionWithLock(PRSessionProviderImpl.java:1397) ~[prprivate-session.jar:?]     at com.pega.pegarules.session.internal.PRSessionProviderImpl.doWithRequestorLocked(PRSessionProviderImpl.java:1140) ~[prprivate-session.jar:?]     at com.pega.pegarules.session.internal.PRSessionProviderImpl.doWithRequestorLocked(PRSessionProviderImpl.java:1021) ~[prprivate-session.jar:?]     at com.pega.pegarules.session.internal.PRSessionProviderImplForModules.doWithRequestorLocked(PRSessionProviderImplForModules.java:71) ~[prprivate-session.jar:?]     at com.pega.platform.executor.queueprocessor.internal.BatchTask.executeInBorrowedRequestor(BatchTask.java:76) ~[pega-executor.jar:?]     at com.pega.platform.executor.queueprocessor.internal.BatchTask.run(BatchTask.java:47) ~[pega-executor.jar:?]     at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:522) ~[?:1.8.0]     at java.util.concurrent.FutureTask.run(FutureTask.java:277) ~[?:1.8.0]     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1160) [?:1.8.0]     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) [?:1.8.0]     at java.lang.Thread.run(Thread.java:818) [?:2.9 (11-06-2019)]