Accessing WorkFlow attributes after execution, using history

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#1

I have a usecase, where i want to extract the a json tree(state) built in workflow execute method. Following is the sample code.

public class TicketWorkFlowImpl implements TicketWorkFlow {

  @Override
  public String execute(Step[] steps){
    JsonNode resultNode..
    //process steps and build resultNode

  }
}

After the workflow is executed, there is another api where i want to fetch the result. I want to use replay or history to fetch the resultNode.
One solution i am thinking is to use the history of events and fetch from the events data

 GetWorkflowExecutionHistoryRequest request = getWorkflowExecutionHistoryRequest(workFlowId);
    GetWorkflowExecutionHistoryResponse resultHistory =
        service.blockingStub().getWorkflowExecutionHistory(request);

    Stream<HistoryEvent> events = resultHistory.getHistory().getEventsList().stream();

But as this is not used as activity input or output parametr i can not get the same.

The second solution i see is create a dummy Activity and pass the resultNode so that it is stored as part of events data.

public class TicketWorkFlowImpl implements TicketWorkFlow {

  @Override
  public String execute(Step[] steps){
    JsonNode resultNode..
    //process steps and build resultNode
     CallResultActivity.record(resultNode)//This is a temporal activity
  }
}

Are there any better ways for the usecase mentioned? Are there any drawbacks with the second solution

#2

There are two ways to solve your problem.

1. Use workflow result

Return the resultNode as the workflow result. Then use the WorkflowStub.getResultAPI to extract the result.

WorkflowClient client = ...;
WorkflowStub workflow = client.newUntypedWorkflowStub("workflowId", Optional.empty(), Optional.of("TicketWorkFlow"));
JsonNode result = workflow.getResult(1, TimeUnit.SECONDS, JsonNode.class);

2. Use query

Add a query method to the workflow interface and call it to return the resultNode. Note that queries work even for closed workflows (up to the retention period).

@WorkflowInterface
public interface TicketWorkflow {
    @WorkflowMethod
    String execute(Step[] steps);

    @QueryMethod
    JsonNode getResultNode();
}

public class TicketWorkFlowImpl implements TicketWorkFlow {

    private JsonNode resultNode;

    @Override
    public JsonNode execute(Step[] steps){
        //process steps and build resultNode

    }

    JsonNode getResultNode() {
        return resultNode;
    }
}

Then use the query to retrieve result:

    WorkflowClient client = WorkflowClient.newInstance();
    TicketWorkFlow workflow = client.newWorkflowStub(TicketWorkFlow, "workflowId", Optional.empty());
    JsonNode result = workflow.getResultNode();
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#3

Thank you @maxim, Using the second solution. It is working

#4

@maxim

We implemented the 2nd solution mentioned.

    JsonNode getResultNode() {
        return resultNode;
    }

But we have a case where we have parentflow - invoking childflow

    WorkflowServiceStubs service = WorkflowServiceStubs.newInstance();
    WorkflowClient client = WorkflowClient.newInstance(service);
    TestWorkFlow jw = client.newWorkflowStub(TestWorkFlow.class, workFlowId, Optional.empty());
    JsonNode node = jw.getNodeResult(path);

When I use this way, the main flow is replayed but it is trying to create new childflow and I see this issue

Caused by: java.lang.IllegalStateException: COMMAND_TYPE_START_CHILD_WORKFLOW_EXECUTION doesn't match EVENT_TYPE_START_CHILD_WORKFLOW_EXECUTION_INITIATED with EventId=5
	at io.temporal.internal.statemachines.WorkflowStateMachines.assertMatch(WorkflowStateMachines.java:784)
	at io.temporal.internal.statemachines.WorkflowStateMachines.validateCommand(WorkflowStateMachines.java:750)
	at io.temporal.internal.statemachines.WorkflowStateMachines.handleCommandEvent(WorkflowStateMachines.java:272)
	at io.temporal.internal.statemachines.WorkflowStateMachines.handleEventImpl(WorkflowStateMachines.java:199)
	at io.temporal.internal.statemachines.WorkflowStateMachines.handleEvent(WorkflowStateMachines.java:178)

Please let me know if I am missing anything
#5

It looks like your workflow code is not determninistic. Make sure that it follows all the constraints outlined in the documentation.

How do you start the child workflow?

#7

Thanks, the below is child workflow creation code
WorkflowClientOptions clientOptions =
WorkflowClientOptions.newBuilder().setNamespace(DEFAULT_NAME_SPACE).build();
WorkflowClient client = WorkflowClient.newInstance(service, clientOptions);
ChildWorkflowOptions options = ChildWorkflowOptions.newBuilder()
.setTaskQueue(Shared.HELLO_WORLD_CHILD_TASK_QUEUE)
.setWorkflowId(workFlowId)
.build();
TestWorkflow workflow = Workflow.newChildWorkflowStub(TestWorkflow.class, options);
This is the code i am using for child workflow

#8

Iā€™m confused. Why are you using WorkflowClient inside the workflow code? It is not allowed as any other RPC calls.

#9

Oh!. Thanks @maixim. I removed that and it is working now.
TestWorkflow workflow = Workflow.newChildWorkflowStub(TestWorkflow.class);

Thanks once again

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