we are seeing below error 30 mins after the load test , not sure what caused it

at com.pega.dsm.dnode.api.dataflow.DataFlowStage$StageOutputSubscriber.onError(DataFlowStage.java:394)
at com.pega.dsm.dnode.api.dataflow.DataFlowStageProcessor.onError(DataFlowStageProcessor.java:48)
at com.pega.dsm.dnode.api.dataflow.DataFlowStage$StageInputSubscriber.onError(DataFlowStage.java:286)
at com.pega.dsm.dnode.api.dataflow.DataFlowExecutor$SynchronousDataFlowExecutor.doOnError(DataFlowExecutor.java:340)
at com.pega.dsm.dnode.api.dataflow.DataFlow$4$1.doOnError(DataFlow.java:338)
at com.pega.dsm.dnode.api.dataflow.DataFlowStage$StageInputSubscriber.onNext(DataFlowStage.java:261)
at com.pega.dsm.dnode.api.dataflow.DataFlowStage$StageInputSubscriber.onNext(DataFlowStage.java:184)
at com.pega.dsm.dnode.api.dataflow.DataFlowExecutor$SynchronousDataFlowExecutor.doOnNext(DataFlowExecutor.java:333)
at com.pega.dsm.dnode.api.dataflow.DataFlowStage$StageOutputSubscriber.onNext(DataFlowStage.java:371)
at com.pega.dsm.dnode.api.dataflow.DataFlowStage$StageOutputSubscriber.onNext(DataFlowStage.java:341)
at com.pega.dsm.dnode.api.dataflow.DataFlowStage$StageInputSubscriber.onNext(DataFlowStage.java:259)
at com.pega.dsm.dnode.api.dataflow.DataFlowStage$StageInputSubscriber.onNext(DataFlowStage.java:184)
at com.pega.dsm.dnode.impl.stream.DataObservableImpl$SafeDataSubscriber.onNext(DataObservableImpl.java:272)
at com.pega.dsm.dnode.api.stream.DataObservables$2.emit(DataObservables.java:57)
at com.pega.dsm.dnode.impl.stream.DataObservableImpl$SafeDataSubscriber.subscribe(DataObservableImpl.java:320)
at com.pega.dsm.dnode.impl.stream.DataObservableImpl.subscribe(DataObservableImpl.java:52)
at com.pega.dsm.dnode.api.dataflow.DataFlow$4.emit(DataFlow.java:343)
at com.pega.dsm.dnode.impl.stream.DataObservableImpl$SafeDataSubscriber.subscribe(DataObservableImpl.java:320)
at com.pega.dsm.dnode.impl.stream.DataObservableImpl.subscribe(DataObservableImpl.java:52)
at com.pega.dsm.dnode.impl.stream.DataObservableImpl.await(DataObservableImpl.java:98)
at com.pega.dsm.dnode.impl.stream.DataObservableImpl.toList(DataObservableImpl.java:77)
at com.pegarules.generated.activity.ra_action_pxrunsinglecaseddf_8a4ad3eceacff2e6e344115ad53989ab.step1_circum0(ra_action_pxrunsinglecaseddf_8a4ad3eceacff2e6e344115ad53989ab.java:179)
at com.pegarules.generated.activity.ra_action_pxrunsinglecaseddf_8a4ad3eceacff2e6e344115ad53989ab.perform(ra_action_pxrunsinglecaseddf_8a4ad3eceacff2e6e344115ad53989ab.java:71)
at com.pega.pegarules.session.internal.mgmt.Executable.doActivity(Executable.java:3505)
at com.pega.pegarules.session.internal.mgmt.Executable.invokeActivity(Executable.java:10563)
at com.pegarules.generated.activity.ra_action_updateresponsedf_c01fcc83a3cf3e4dedda72ba9cad1e18.step4_circum0(ra_action_updateresponsedf_c01fcc83a3cf3e4dedda72ba9cad1e18.java:424)
at com.pegarules.generated.activity.ra_action_updateresponsedf_c01fcc83a3cf3e4dedda72ba9cad1e18.perform(ra_action_updateresponsedf_c01fcc83a3cf3e4dedda72ba9cad1e18.java:104)
at com.pega.pegarules.session.internal.mgmt.Executable.doActivity(Executable.java:3505)
at com.pega.pegarules.session.internal.mgmt.Executable.invokeActivity(Executable.java:10563)
at com.pegarules.generated.activity.ra_action_svcsetdispositions_fee063de4e593956660d7be662974d1c.step6_circum0(ra_action_svcsetdispositions_fee063de4e593956660d7be662974d1c.java:551)
at com.pegarules.generated.activity.ra_action_svcsetdispositions_fee063de4e593956660d7be662974d1c.perform(ra_action_svcsetdispositions_fee063de4e593956660d7be662974d1c.java:166)
at com.pega.pegarules.session.internal.mgmt.Executable.doActivity(Executable.java:3505)
at com.pega.pegarules.session.internal.mgmt.base.ThreadRunner.runActivitiesAlt(ThreadRunner.java:646)
at com.pega.pegarules.session.internal.mgmt.PRThreadImpl.runActivitiesAlt(PRThreadImpl.java:461)
at com.pega.pegarules.integration.engine.internal.services.ServiceAPI.runActivities(ServiceAPI.java:1882)
at com.pega.pegarules.session.external.engineinterface.service.EngineAPI.processRequestInner(EngineAPI.java:385)
at sun.reflect.GeneratedMethodAccessor84.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.pega.pegarules.session.internal.PRSessionProviderImpl.performTargetActionWithLock(PRSessionProviderImpl.java:1270)
at com.pega.pegarules.session.internal.PRSessionProviderImpl.doWithRequestorLocked(PRSessionProviderImpl.java:1008)
at com.pega.pegarules.session.internal.PRSessionProviderImpl.doWithRequestorLocked(PRSessionProviderImpl.java:841)
at com.pega.pegarules.session.external.engineinterface.service.EngineAPI.processRequest(EngineAPI.java:331)
at com.pega.pegarules.integration.engine.internal.services.http.HTTPService.invoke(HTTPService.java:416)
at com.pega.pegarules.session.internal.engineinterface.etier.impl.EngineImpl._invokeEngine_privact(EngineImpl.java:315)
at com.pega.pegarules.session.internal.engineinterface.etier.impl.EngineImpl.invokeEngine(EngineImpl.java:263)
at com.pega.pegarules.session.internal.engineinterface.etier.impl.EngineImpl.invokeEngine(EngineImpl.java:240)
at com.pega.pegarules.priv.context.JNDIEnvironment.invokeEngineInner(JNDIEnvironment.java:278)
at com.pega.pegarules.priv.context.JNDIEnvironment.invokeEngine(JNDIEnvironment.java:223)
at com.pega.pegarules.web.impl.WebStandardImpl.makeEtierRequest(WebStandardImpl.java:574)
at com.pega.pegarules.web.impl.WebStandardImpl.doPost(WebStandardImpl.java:374)
at sun.reflect.GeneratedMethodAccessor83.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.pega.pegarules.internal.bootstrap.PRBootstrap.invokeMethod(PRBootstrap.java:370)
at com.pega.pegarules.internal.bootstrap.PRBootstrap.invokeMethodPropagatingThrowable(PRBootstrap.java:411)
at com.pega.pegarules.boot.internal.extbridge.AppServerBridgeToPega.invokeMethodPropagatingThrowable(AppServerBridgeToPega.java:223)
at com.pega.pegarules.boot.internal.extbridge.AppServerBridgeToPega.invokeMethod(AppServerBridgeToPega.java:272)
at com.pega.pegarules.internal.web.servlet.WebStandardBoot.doPost(WebStandardBoot.java:121)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:754)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:295)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:231)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:149)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:420)
at org.jboss.as.web.session.ClusteredSessionValve.handleRequest(ClusteredSessionValve.java:134)
at org.jboss.as.web.session.ClusteredSessionValve.invoke(ClusteredSessionValve.java:99)
at org.jboss.as.web.session.JvmRouteValve.invoke(JvmRouteValve.java:92)
at org.jboss.as.web.session.LockingValve.invoke(LockingValve.java:64)
at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:169)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:145)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:97)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:102)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:344)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:856)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:653)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:926)
at java.lang.Thread.run(Thread.java:745)
Caused by: com.pega.dsm.dnode.impl.core.ExceptionWithInputRecord: com.pega.dsm.dnode.api.DNodeException: Cannot execute select statement
... 74 more
Caused by: com.pega.dsm.dnode.api.DNodeException: Cannot execute select statement
at com.pega.dsm.dnode.impl.cassandra.CassandraDao.executeStatement(CassandraDao.java:150)
at com.pega.dsm.dnode.impl.cassandra.CassandraDataRepository.findBy(CassandraDataRepository.java:267)
at com.pega.dsm.dnode.impl.dataset.cassandra.CassandraBrowseByKeysOperation$1.emit(CassandraBrowseByKeysOperation.java:56)
at com.pega.dsm.dnode.impl.stream.DataObservableImpl$SafeDataSubscriber.subscribe(DataObservableImpl.java:320)
at com.pega.dsm.dnode.impl.stream.DataObservableImpl.subscribe(DataObservableImpl.java:52)
at com.pega.dsm.dnode.api.stream.DataObservables$3.emit(DataObservables.java:72)
at com.pega.dsm.dnode.impl.stream.DataObservableImpl$SafeDataSubscriber.subscribe(DataObservableImpl.java:320)
at com.pega.dsm.dnode.impl.stream.DataObservableImpl.subscribe(DataObservableImpl.java:52)
at com.pega.dsm.dnode.impl.stream.DataObservableImpl.await(DataObservableImpl.java:98)
at com.pega.dsm.dnode.impl.stream.DataObservableImpl.await(DataObservableImpl.java:87)
at com.pega.dsm.dnode.impl.dataflow.strategy.DelayedLearning.loadPreviousResults(DelayedLearning.java:74)
at com.pega.dsm.dnode.impl.dataflow.strategy.StrategyStageProcessor.onNext(StrategyStageProcessor.java:111)
at com.pega.dsm.dnode.api.dataflow.DataFlowStageBatchProcessor.commitBatchInternal(DataFlowStageBatchProcessor.java:102)
at com.pega.dsm.dnode.api.dataflow.DataFlowStageBatchProcessor.onNext(DataFlowStageBatchProcessor.java:57)
at com.pega.dsm.dnode.api.dataflow.DataFlowStageBatchProcessor.onNext(DataFlowStageBatchProcessor.java:17)
at com.pega.dsm.dnode.api.dataflow.DataFlowStage$StageInputSubscriber.onNext(DataFlowStage.java:259)
... 73 more
Caused by: org.apache.cassandra.exceptions.ReadTimeoutException: Operation timed out - received only 0 responses.
at org.apache.cassandra.service.ReadCallback.get(ReadCallback.java:105)
at org.apache.cassandra.service.StorageProxy.fetchRows(StorageProxy.java:943)
at org.apache.cassandra.service.StorageProxy.read(StorageProxy.java:828)
at org.apache.cassandra.cql3.statements.SelectStatement.execute(SelectStatement.java:140)
at com.pega.dsm.dnode.impl.cassandra.CassandraDao.executeStatement(CassandraDao.java:144)
... 88 more

***Updated by moderator: Lochan to update Categories***