question Custom NiFi processor gets "ControllerServices may be referenced only via their interfaces" error. in Archives of Support Questions (Read Only)

Custom NiFi processor gets "ControllerServices may be referenced only via their interfaces" error.

ajviradia — Wed, 01 Mar 2017 06:48:48 GMT

I have built a custom controller service and custom processor. I am able to build and run tests in IntelliJ on my laptop. Once the maven build is successfully complete, I copied all the 3 nar files and dropped them in the lib folder of NiFi.

In NiFi web interface, I can the see my custom service in Controller Service page. I am able to configure it and enable it. NiFi logs confirms the service is online. Now, when I drop the custom processor, I cannot see the service to choose in drop down. Event though it is service is running.

I verified the dependencies in pom for all nar modules.

nifi-customservice-api-nar
nifi-customservice-nar
nifi-LookupProcessor-nar

Following is the error in the NiFi app log:

java.lang.IllegalArgumentException: ControllerServices may be referenced only via their interfaces; class org.pwc.nifi.customservice.LookupService is not an interface at org.apache.nifi.attribute.expression.language.StandardPropertyValue.asControllerService(StandardPropertyValue.java:172) ~[nifi-expression-language-1.1.1.jar:1.1.1] at org.pwc.nifi.customservice.LookupProcessor.onTrigger(LookupProcessor.java:79) ~[na:na] at org.apache.nifi.processor.AbstractProcessor.onTrigger(AbstractProcessor.java:27) ~[nifi-api-1.1.1.jar:1.1.1] at org.apache.nifi.controller.StandardProcessorNode.onTrigger(StandardProcessorNode.java:1099) ~[nifi-framework-core-1.1.1.jar:1.1.1] at org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:136) [nifi-framework-core-1.1.1.jar:1.1.1] at org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:47) [nifi-framework-core-1.1.1.jar:1.1.1] at org.apache.nifi.controller.scheduling.TimerDrivenSchedulingAgent$1.run(TimerDrivenSchedulingAgent.java:132) [nifi-framework-core-1.1.1.jar:1.1.1] at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [na:1.8.0_91] at java.util.concurrent.FutureTask.runAndReset(Unknown Source) [na:1.8.0_91] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(Unknown Source) [na:1.8.0_91] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source) [na:1.8.0_91] at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [na:1.8.0_91] at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [na:1.8.0_91] at java.lang.Thread.run(Unknown Source) [na:1.8.0_91]

I would appreciate if someone can help with :

Resolving missing service in drop down when configuring the processor in properties.
Resolving error "java.lang.IllegalArgumentException: ControllerServices may be referenced only via their interfaces"

Thank you.

Re: Custom NiFi processor gets "ControllerServices may be referenced only via their interfaces" error.

bbende — Wed, 01 Mar 2017 22:03:50 GMT

It is hard to tell without being able to see your code, but it seems like this is saying that in LookupProcessor you have a PropertyDescriptor that represents a Controller Service, but the class you specified is not the interface from nifi-customservice-api-nar, but instead it is the implementation from nifi-customservice-nar.

As an example, InvokeHttp uses SSLContextService:

https://github.com/apache/nifi/blob/master/nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/InvokeHTTP.java#L205

SSLContextService is the interface that comes from nifi-standard-services-api:

https://github.com/apache/nifi/blob/master/nifi-nar-bundles/nifi-standard-services/nifi-ssl-context-service-api/src/main/java/org/apache/nifi/ssl/SSLContextService.java

The implementation is StandardSSLContextService which is is nifi-ssl-context-bundle:

https://github.com/apache/nifi/blob/master/nifi-nar-bundles/nifi-standard-services/nifi-ssl-context-bundle/nifi-ssl-context-service/src/main/java/org/apache/nifi/ssl/StandardSSLContextService.java

Re: Custom NiFi processor gets "ControllerServices may be referenced only via their interfaces" error.

ajviradia — Thu, 02 Mar 2017 01:16:24 GMT

Your explanation helped me in identify the core issue. You are correct in assuming I was calling the service implementation rather than the interface. Once I made appropriate changes in my code and unit tested, I was able to drop in NiFi and have the integration testing done.

I was able to configure the custom service by adding it in drop down on the custom Lookup processor in NiFi Web UI.

THANK YOU for all the help!!!!