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Interceptors

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Interceptors wrap inbound and outbound Temporal calls so you can apply shared behavior such as tracing, logging, or authorization. See Interceptors for the inbound vs outbound model.

Register them on the Client (WorkflowClientOptions.Builder.setInterceptors) or the Worker Factory (WorkerFactoryOptions.Builder.setWorkerInterceptors). Full API: io.temporal.common.interceptors.

Several interceptor APIs are marked @Experimental.

Implement a Client interceptor​

Extend WorkflowClientInterceptorBase and override workflowClientCallsInterceptor to return a WorkflowClientCallsInterceptor that wraps next. Override only the calls you want to intercept; forward the rest to next (or to super, if you extend WorkflowClientCallsInterceptorBase).

public class TracingClientInterceptor extends WorkflowClientInterceptorBase {
  @Override
  public WorkflowClientCallsInterceptor workflowClientCallsInterceptor(
      WorkflowClientCallsInterceptor next) {
    return new WorkflowClientCallsInterceptorBase(next) {
      @Override
      public WorkflowStartOutput start(WorkflowStartInput input) {
        System.out.println("starting workflow " + input.getWorkflowId());
        return super.start(input);
      }
    };
  }
}

Register the interceptor when you build the Client:

WorkflowClientOptions clientOptions =
    WorkflowClientOptions.newBuilder().setInterceptors(new TracingClientInterceptor()).build();
WorkflowClient client = WorkflowClient.newInstance(service, clientOptions);

Implement a Worker interceptor​

Extend WorkerInterceptorBase and override interceptWorkflow, interceptActivity, or both, for the inbound call chains you need. Each inbound interceptor must forward every override to next. To also intercept outbound calls made from inside the Workflow, wrap the WorkflowOutboundCallsInterceptor passed to init and forward that wrapper to next.init(...):

public class TracingWorkerInterceptor extends WorkerInterceptorBase {
  @Override
  public WorkflowInboundCallsInterceptor interceptWorkflow(WorkflowInboundCallsInterceptor next) {
    return new WorkflowInboundCallsInterceptorBase(next) {
      @Override
      public void init(WorkflowOutboundCallsInterceptor outboundCalls) {
        next.init(
            new WorkflowOutboundCallsInterceptorBase(outboundCalls) {
              @Override
              public <R> ActivityOutput<R> executeActivity(ActivityInput<R> input) {
                Workflow.getLogger(TracingWorkerInterceptor.class)
                    .info("starting activity " + input.getActivityName());
                return super.executeActivity(input);
              }
            });
      }
    };
  }
}

Register the interceptor on the Worker Factory:

WorkerFactoryOptions factoryOptions =
    WorkerFactoryOptions.newBuilder().setWorkerInterceptors(new TracingWorkerInterceptor()).build();
WorkerFactory factory = WorkerFactory.newInstance(client, factoryOptions);
Workflow interceptors and replay

Workflow interceptor methods also run during replay. Use replay-safe APIs for logging, randomness, and time.