How to replay a Workflow Execution in Java

To replay Workflow Executions, use the WorkflowReplayer class in the temporal-testing package.

In the following example, Event Histories are downloaded from the server, and then replayed. Note that this requires Advanced Visibility to be enabled.

// Note we assume you already have a WorkflowServiceStubs (`service`) and WorkflowClient (`client`)
// in scope.
ListWorkflowExecutionsRequest listWorkflowExecutionRequest =
    ListWorkflowExecutionsRequest.newBuilder()
        .setNamespace(client.getOptions().getNamespace())
        .setQuery("TaskQueue = 'mytaskqueue'")
        .build();
ListWorkflowExecutionsResponse listWorkflowExecutionsResponse =
    service.blockingStub().listWorkflowExecutions(listWorkflowExecutionRequest);
List<WorkflowExecutionHistory> histories =
    listWorkflowExecutionsResponse.getExecutionsList().stream()
        .map(
            (info) -> {
              GetWorkflowExecutionHistoryResponse weh =
                  service.blockingStub().getWorkflowExecutionHistory(
                      GetWorkflowExecutionHistoryRequest.newBuilder()
                          .setNamespace(testEnvironment.getNamespace())
                          .setExecution(info.getExecution())
                          .build());
              return new WorkflowExecutionHistory(
                  weh.getHistory(), info.getExecution().getWorkflowId());
            })
        .collect(Collectors.toList());


WorkflowReplayer.replayWorkflowExecutions(
    histories, true, WorkflowA.class, WorkflowB.class, WorkflowC.class);

In the next example, a single history is loaded from a JSON file on disk:

File file = new File("my_history.json");
WorkflowReplayer.replayWorkflowExecution(file, MyWorkflow.class);

In both examples, if Event History is non-deterministic, an error is thrown. You can choose to wait until all histories have been replayed with replayWorkflowExecutions by setting the failFast argument to false.