Package io.temporal.common.context

Interface ContextPropagator

  • public interface ContextPropagator
    Context Propagators are used to propagate information from the workflow client to workflow execution, workflow to activity, workflow to child workflow, and workflow to child thread created using Async.
    The propagation works from top to bottom, lower level contexts are not propagated back to the top.

    A sample ContextPropagator that copies all MDC entries starting with a given prefix along the code path looks like this: 

    
 public class MDCContextPropagator implements ContextPropagator {
   public String getName() {
     return this.getClass().getName();
   }

   public Object getCurrentContext() {
     Map<String, String> context = new HashMap<>();
     for (Map.Entry<String, String> entry : MDC.getCopyOfContextMap().entrySet()) {
       if (entry.getKey().startsWith("X-")) {
         context.put(entry.getKey(), entry.getValue());
       }
     }
     return context;
   }

   public void setCurrentContext(Object context) {
     Map<String, String> contextMap = (Map<String, String>) context;
     for (Map.Entry<String, String> entry : contextMap.entrySet()) {
       MDC.put(entry.getKey(), entry.getValue());
     }
   }

   public Map<String, Payload> serializeContext(Object context) {
     Map<String, String> contextMap = (Map<String, String>) context;
     Map<String, Payload> serializedContext = new HashMap<>();
     for (Map.Entry<String, String> entry : contextMap.entrySet()) {
       serializedContext.put(entry.getKey(), DataConverter.getDefaultInstance().toPayload(entry.getValue()).get());
     }
     return serializedContext;
   }

   public Object deserializeContext(Map<String, Payload> context) {
     Map<String, String> contextMap = new HashMap<>();
     for (Map.Entry<String, Payload> entry : context.entrySet()) {
       contextMap.put(entry.getKey(), DataConverter.getDefaultInstance().fromPayload(entry.getValue(), String.class, String.class));
     }
     return contextMap;
   }
 }
    To set up the context propagators, you must configure them during creation of WorkflowClient on both client/stubs and worker side: 
    
 WorkflowClientOptions options = WorkflowClientOptions.newBuilder()
                 .setContextPropagators(Collections.singletonList(new MDCContextPropagator()))
                 .build();
 WorkflowClient client = WorkflowClient.newInstance(service, factoryOptions);

 Workflow workflow = client.newWorkflowStub(Workflow.class,
                WorkflowOptions.newBuilder().setTaskQueue("taskQueue").build());
 //or
 WorkerFactory workerFactory = WorkerFactory.newInstance(client);

    If you wish to override them for a workflow stub or a child workflow, you can do so when creating a
    WorkflowStub: 
    
 Workflow workflow = client.newWorkflowStub(Workflow.class,
                WorkflowOptions.newBuilder()
                        //...
                        .setContextPropagators(Collections.singletonList(new MDCContextPropagator()))
                        .build());

    ChildWorkflowStub: 
    
 ChildWorkflow childWorkflow = Workflow.newChildWorkflowStub(ChildWorkflow.class,
                ChildWorkflowOptions.newBuilder()
                        .setContextPropagators(Collections.singletonList(new MDCContextPropagator()))
                        .build());

    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      java.lang.Object deserializeContext​(java.util.Map<java.lang.String,​io.temporal.api.common.v1.Payload> header)
      Turn the serialized header data into context object(s)
      java.lang.Object getCurrentContext()
      Returns the current context in object form
      java.lang.String getName()
      Returns the unique name of the context propagator.
      java.util.Map<java.lang.String,​io.temporal.api.common.v1.Payload> serializeContext​(java.lang.Object context)
      Given context data, serialize it for transmission in the RPC header.
      void setCurrentContext​(java.lang.Object context)
      Sets the current context

    • Method Detail

      • getName

        java.lang.String getName()
        Returns the unique name of the context propagator. This name is used to store and address context objects to pass them between threads. This name is not used for serialization, serialization is fully controlled by serializeContext(Object)
        Returns:
        The unique name of this propagator.

      • serializeContext

        java.util.Map<java.lang.String,​io.temporal.api.common.v1.Payload> serializeContext​(java.lang.Object context)
        Given context data, serialize it for transmission in the RPC header.

        Note: keys of the result map should have unique values across all propagators and interceptors, because they all share the same single keyspace of a single instance of temporal.api.common.v1.Header

        Returns:
        serialized representation to be sent in request temporal.api.common.v1.Header

      • deserializeContext

        java.lang.Object deserializeContext​(java.util.Map<java.lang.String,​io.temporal.api.common.v1.Payload> header)
        Turn the serialized header data into context object(s)

      • getCurrentContext

        java.lang.Object getCurrentContext()
        Returns the current context in object form

      • setCurrentContext

        void setCurrentContext​(java.lang.Object context)
        Sets the current context