ExternalTasks - fetchAndLock NullPointerException

Kikol · May 28, 2018, 6:28am

Hi,
I want play with external tasks pattern but whenever I call fetchAndLock method I always receive HTTP 500:

{
“timestamp”: “2018-05-28T06:22:30.103+0000”,
“status”: 500,
“error”: “Internal Server Error”,
“message”: “No message available”,
“path”: “/rest/engine/default/external-task/fetchAndLock”
}

When I look at Camunda console I see NullPointerException when gathering FetchAndLockHandler from FetchAndLockRestServiceImpl:

java.lang.NullPointerException: null
at org.camunda.bpm.engine.rest.impl.FetchAndLockRestServiceImpl.fetchAndLock(FetchAndLockRestServiceImpl.java:34)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)

What am I doing wrong?

thorben · May 28, 2018, 9:44am

Which Camunda version do you use?

Kikol · May 28, 2018, 10:35am

Newest one: 3.0.0.

thorben · May 28, 2018, 2:44pm

Please check if you have the same problem with 2.3.0.

Kikol · May 28, 2018, 7:27pm

Same problem with version 2.3. I suspect some problems with my input.
Here is a post body:

{
“workerId”:“myWorker”,
“maxTasks”:23,
“topics”:
[{“topicName”: “DoSomething”,
“lockDuration”: 10000
}]
}
Unfortunately I’m unable to paste my diagram here due to newbie limitations

thorben · May 29, 2018, 11:55am

The request body looks fine to me and judging by the stacktrace it is not the request body that is the problem. Could you maybe share a minimal project on github with exact steps to reproduce the exception?

Thanks,
Thorben

sadelmichal · May 29, 2018, 4:01pm

The problem lies somewhere in the setup. The fetchAndLockHandler is never initialized in FetchAndLockContextListener, because listener is never added to the rest servlet. One solution is to produce a bean in a @Configuration class.

@Bean
public ServletContextListener fetchAndLockContextListener(){
 return new FetchAndLockContextListener();
}

But probably this is not a solution, rather a quick fix to move on.

Example @github

tasso94 · May 30, 2018, 7:32am

Hi,

we’re currently investigating the issue and come back to you in a bit.

Cheers,
Tassilo

sdorokhova · May 30, 2018, 8:25am

Hi Michał,
than you for reporting the issue, I’ve created the issue for it (https://app.camunda.com/jira/browse/CAM-9111) and will try to quickly fix it (within 3.0.0, which is not officially released yet )

But your fix it totally fine, you can use it so far.

Cheers,
Svetlana

bensopra · June 28, 2019, 3:36pm

Hi,

I use Camunda docker image (camunda/camunda-bpm-platform:tomcat-7.11.0) and I’m unable to use /external-task/fetchAndLock API as described above.

Can you please help me to get it work with my configuration ?

Thanks.

steel · October 16, 2019, 2:32pm

I am experiencing this as well on 7.11.3 since upgrading from 7.8. Were you able to resolve your issue ?

Niall · October 16, 2019, 3:23pm

What exactly is going wrong?
Can you give us more information of exactly what you’re trying and how it’s failing?

steel · October 17, 2019, 6:12am

Hi Niall!

I am making an api call to engine-rest/external-task/fetchAndLock
The body looks like this:

{“maxTasks”:300,“workerId”:“98e3f029-2345-4820-99ec-6a0dd298da53”,“usePriority”:false,“topics”:[{“topicName”:“xxxxxxxx”,“lockDuration”:30000,“variables”:[“y”]},{“topicName”:“yyyyy”,“lockDuration”:30000,“variables”:[“z”,“group”,“type”]},{“topicName”:“wwwwww”,“lockDuration”:20000,“variables”:[“a”,“b”]}]}

and the response is a 500 with {“type”:“NullPointerException”,“message”:null}

and in the logs I see

WARNING [http-nio-8080-exec-10] org.camunda.bpm.engine.rest.exception.ExceptionHandler.toResponse java.lang.NullPointerException
at org.camunda.bpm.engine.rest.impl.FetchAndLockRestServiceImpl.fetchAndLock(FetchAndLockRestServiceImpl.java:38)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498) 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.invokePropagateNotFound(SynchronousDispatcher.java:251)
at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:232)
at org.jboss.resteasy.plugins.server.servlet.FilterDispatcher.doFilter(FilterDispatcher.java:62)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.camunda.engine.auth.jwt.JwtEngineAuthenticationFilter.doFilter(JwtEngineAuthenticationFilter.java:89)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.filters.CorsFilter.handleNonCORS(CorsFilter.java:352)
at org.apache.catalina.filters.CorsFilter.doFilter(CorsFilter.java:171)
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:200)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490)
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$ConnectionHandler.process(AbstractProtocol.java:836)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1747)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

Niall · October 17, 2019, 6:17am

Beyond changing the version of Camunda is there anything you else you changed before the call stopped working?
Also can you upload the full log file?

Yana · October 17, 2019, 9:54am

Hi @steel,

Additional to Niall questions, could you please share an example of your project so we can reproduce it on our side?

Yana · October 17, 2019, 11:41am

@steel, keep in mind if you use an enterprise version, you can also raise a support issue

steel · October 17, 2019, 11:44am

Thank you. I am going to get back with more info in the next day. I am going to start with a fresh install and test the end point and incrementally apply our changes where possible.

steel · October 23, 2019, 8:55am

After some investigation it appears that the issue is related to an outdate web.xml in the engine-rest folder (due to maintaining our own customized version of this file).

We did not have the additional mappings for -

org.camunda.bpm.engine.rest.impl.FetchAndLockContextListener

It would be great if an error message could be generated to point to this missing config being a problem.

Thanks for the help!