Fetch And Lock Fail with "NullReferenceExcption" after increasing retries of failed external task

Hi,

we have some issues with calling "engine-rest/external-task/fetchAndLock":

1. We have on external task that failed. That's why the task is set to incident state. Import: The incident has an error message but no error details.
2.  First problem: If we click on the error message in camunda cockpit, we get the following message: "Server Error : The server reported an internal error. Try to refresh the page or login and out of the application."
3. If we now increase the retries in Camunda cockpit and we call "engine-rest/external-task/fetchAndLock" the we get the following result via REST-API:

{
    "type": "NullPointerException",
    "message": null
}
In our log we find the following stack trace

 

17-Feb-2020 10:22:51.127 SEVERE [http-nio-8080-exec-11] org.camunda.commons.logging.BaseLogger.logError ENGINE-16004 Exception while closing command context: null

                java.lang.NullPointerException

                               at java.base/java.lang.String.<init>(String.java:561)

                               at org.camunda.bpm.engine.impl.util.StringUtil.fromBytes(StringUtil.java:126)

                               at org.camunda.bpm.engine.impl.util.StringUtil.fromBytes(StringUtil.java:112)

                               at org.camunda.bpm.engine.impl.util.ExceptionUtil.getExceptionStacktrace(ExceptionUtil.java:46)

                               at org.camunda.bpm.engine.impl.persistence.entity.ExternalTaskEntity.getErrorDetails(ExternalTaskEntity.java:278)

                               at org.camunda.bpm.engine.impl.externaltask.LockedExternalTaskImpl.fromEntity(LockedExternalTaskImpl.java:150)

                               at org.camunda.bpm.engine.impl.cmd.FetchExternalTasksCmd.execute(FetchExternalTasksCmd.java:79)

                               at org.camunda.bpm.engine.impl.cmd.FetchExternalTasksCmd.execute(FetchExternalTasksCmd.java:40)

                               at org.camunda.bpm.engine.impl.interceptor.CommandExecutorImpl.execute(CommandExecutorImpl.java:28)

                               at org.camunda.bpm.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:110)

                               at org.camunda.bpm.engine.impl.interceptor.ProcessApplicationContextInterceptor.execute(ProcessApplicationContextInterceptor.java:70)

                               at org.camunda.bpm.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:33)

                               at org.camunda.bpm.engine.impl.externaltask.ExternalTaskQueryTopicBuilderImpl.execute(ExternalTaskQueryTopicBuilderImpl.java:60)

                               at org.camunda.bpm.engine.rest.impl.FetchAndLockHandlerImpl.executeFetchAndLock(FetchAndLockHandlerImpl.java:268)

                               at org.camunda.bpm.engine.rest.impl.FetchAndLockHandlerImpl.tryFetchAndLock(FetchAndLockHandlerImpl.java:251)

                               at org.camunda.bpm.engine.rest.impl.FetchAndLockHandlerImpl.addPendingRequest(FetchAndLockHandlerImpl.java:316)

                               at org.camunda.bpm.engine.rest.impl.FetchAndLockRestServiceImpl.fetchAndLock(FetchAndLockRestServiceImpl.java:38)

                               at jdk.internal.reflect.GeneratedMethodAccessor2155.invoke(Unknown Source)

                               at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

                               at java.base/java.lang.reflect.Method.invoke(Method.java:566)

                               at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:140)

                               at org.jboss.resteasy.core.ResourceMethodInvoker.invokeOnTarget(ResourceMethodInvoker.java:295)

                               at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:249)

                               at org.jboss.resteasy.core.ResourceLocatorInvoker.invokeOnTargetObject(ResourceLocatorInvoker.java:138)

                               at org.jboss.resteasy.core.ResourceLocatorInvoker.invoke(ResourceLocatorInvoker.java:101)

                               at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:406)

                               at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:213)

                               at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:228)

                               at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:56)

                               at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:51)

                               at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)

                               at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)

                               at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

                               at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

                               at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

                               at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

                               at org.camunda.bpm.engine.rest.filter.CacheControlFilter.doFilter(CacheControlFilter.java:45)

                               at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

                               at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

                               at org.camunda.bpm.engine.rest.filter.EmptyBodyFilter.doFilter(EmptyBodyFilter.java:99)

                               at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

                               at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

                               at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)

                               at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)

                               at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:526)

                               at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)

                               at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)

                               at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:678)

                               at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)

                               at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)

                               at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)

                               at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)

                               at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860)

                               at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1587)

                               at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)

                               at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)

                               at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)

                               at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

                               at java.base/java.lang.Thread.run(Thread.java:834)

Problem seems that the field "bytes_" in CAMUNDA.ACT_GE_BYTEARRAY is null because we do not provide error details.

We are using version 7.12-ee.

Can you please check this.

 

BR

Christian