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Features - Java SDK feature guide

The Features section of the Temporal Developer's guide provides basic implementation guidance on how to use many of the development features available to Workflows and Activities in the Temporal Platform.

In this section you can find the following:

How to develop with Signals​

A Signal is a message sent to a running Workflow Execution.

Signals are defined in your code and handled in your Workflow Definition. Signals can be sent to Workflow Executions from a Temporal Client or from another Workflow Execution.

How to define a Signal​

A Signal has a name and can have arguments.

  • The name, also called a Signal type, is a string.
  • The arguments must be serializable.

The @SignalMethod annotation indicates that the method is used to handle and react to external Signals.

@SignalMethod
   void mySignal(String signalName);

The method can have parameters that contain the Signal payload and must be serializable by the default Jackson JSON Payload Converter.

void mySignal(String signalName, Object... args);

This method does not return a value and must have a void return type.

Things to consider when defining Signals:

  • Use Workflow object constructors and initialization blocks to initialize the internal data structures if possible.
  • Signals might be received by a Workflow before the Workflow method is executed. When implementing Signals in scenarios where this can occur, assume that no parts of Workflow code ran. In some cases, Signal method implementation might require some initialization to be performed by the Workflow method code first—for example, when the Signal processing depends on, and is defined by the Workflow input. In this case, you can use a flag to determine whether the Workflow method is already triggered; if not, persist the Signal data into a collection for delayed processing by the Workflow method.

How to handle Signals in an Workflow in Java​

Workflows listen for Signals by the Signal's name.

Use the @SignalMethod annotation to handle Signals in the Workflow interface.

The Signal type defaults to the name of the method. In the following example, the Signal type defaults to retryNow.

@WorkflowInterface
public interface FileProcessingWorkflow {

   @WorkflowMethod
   String processFile(Arguments args);

   @SignalMethod
   void retryNow();
}

To overwrite this default naming and assign a custom Signal type, use the @SignalMethod annotation with the name parameter. In the following example, the Signal type is set to retrysignal.

@WorkflowInterface
public interface FileProcessingWorkflow {

   @WorkflowMethod
   String processFile(Arguments args);

   @SignalMethod(name = "retrysignal")
   void retryNow();
}

A Workflow interface can define any number of methods annotated with @SignalMethod, but the method names or the name parameters for each must be unique.

In the following example, we define a Signal method updateGreeting to update the greeting in the Workflow. We set a Workflow.await in the Workflow implementation to block the current Workflow Execution until the provided unblock condition is evaluated to true. In this case, the unblocking condition is evaluated to true when the Signal to update the greeting is received.

@WorkflowInterface
public interface HelloWorld {
    @WorkflowMethod
    void sayHello(String name);

    @SignalMethod
    void updateGreeting(String greeting);
}
public class HelloWorldImpl implements HelloWorld {
    private final Logger workflowLogger = Workflow.getLogger(HelloWorldImpl.class);
    private String greeting;

    @Override
    public void sayHello(String name) {
        int count = 0;
        while (!"Bye".equals(greeting)) {
            String oldGreeting = greeting;
            Workflow.await(() -> !Objects.equals(greeting, oldGreeting));
        }
        workflowLogger.info(++count + ": " + greeting + " " + name + "!");
    }

    @Override
    public void updateGreeting(String greeting) {
        this.greeting = greeting;
    }
}

This Workflow completes when the Signal updates the greeting to Bye.

How to send a Signal from a Temporal Client​

When a Signal is sent successfully from the Temporal Client, the WorkflowExecutionSignaled Event appears in the Event History of the Workflow that receives the Signal.

To send a Signal to a Workflow Execution from a Client, call the Signal method, annotated with @SignalMethod in the Workflow interface, from the Client code.

In the following Client code example, we start the Workflow greetCustomer and call the Signal method addCustomer that is handled in the Workflow.

// create a typed Workflow stub for GreetingsWorkflow
GreetingsWorkflow workflow = client.newWorkflowStub(GreetingsWorkflow.class,
        WorkflowOptions.newBuilder()
                // set the Task Queue
                .setTaskQueue(taskQueue)
                // Workflow Id is recommended but not required
                .setWorkflowId(workflowId)
                .build());

// start the Workflow
WorkflowClient.start(workflow::greetCustomer);
// send a Signal to the Workflow
Customer customer = new Customer("John", "Spanish", "john@john.com");
workflow.addCustomer(customer); //addCustomer is the Signal method defined in the greetCustomer Workflow.

See Handle Signals for details on how to handle Signals in a Workflow.

How to send a Signal from a Workflow​

A Workflow can send a Signal to another Workflow, in which case it's called an External Signal.

When an External Signal is sent:

To send a Signal from within a Workflow to a different Workflow Execution, initiate an ExternalWorkflowStub in the implementation of the current Workflow and call the Signal method defined in the other Workflow.

The following example shows how to use an untyped ExternalWorkflowStub in the Workflow implementation to send a Signal to another Workflow.

    public String sendGreeting(String name) {

        // initiate ExternalWorkflowStub to call another Workflow by its Id "ReplyWF"
        ExternalWorkflowStub callRespondWorkflow = Workflow.newUntypedExternalWorkflowStub("ReplyWF");

        String responseTrigger = activity.greeting("Hello", name);

        // send a Signal from this sendGreeting Workflow to the other Workflow
        // by calling the Signal method name "getGreetCall" defined in that Workflow.
        callRespondWorkflow.signal("getGreetCall", responseTrigger);

        return responseTrigger;

How to send a Signal-with-Start in Java​

Signal-With-Start is used from the Client. It takes a Workflow Id, Workflow arguments, a Signal name, and Signal arguments.

If there's a Workflow running with the given Workflow Id, it will be signaled. If there isn't, a new Workflow will be started and immediately signaled.

To send Signals to a Workflow Execution whose status is unknown, use SignalWithStart with a WorkflowStub in the Client code. This method ensures that if the Workflow Execution is in a closed state, a new Workflow Execution is spawned and the Signal is delivered to the running Workflow Execution.

Note that when the SignalwithStart spawns a new Workflow Execution, the Signal is delivered before the call to your @WorkflowMethod. This means that the Signal handler in your Workflow interface code will execute before the @WorkfowMethod. You must ensure that your code logic can deal with this.

In the following example, the Client code uses SignalwithStart to send the Signal setCustomer to the UntypedWorkflowStub named GreetingWorkflow. If the GreetingWorkflow Workflow Execution is not running, the SignalwithStart starts the Workflow Execution.

...
public static void signalWithStart() {
        // WorkflowStub is a client-side stub to a single Workflow instance
        WorkflowStub untypedWorkflowStub = client.newUntypedWorkflowStub("GreetingWorkflow",
        WorkflowOptions.newBuilder()
                .setWorkflowId(workflowId)
                .setTaskQueue(taskQueue)
                .build());

        untypedWorkflowStub.signalWithStart("setCustomer", new Object[] {customer2}, new Object[] {customer1});

        printWorkflowStatus();

        try {
            String greeting = untypedWorkflowStub.getResult(String.class);
            printWorkflowStatus();
            System.out.println("Greeting: " + greeting);
        } catch(WorkflowFailedException e) {
            System.out.println("Workflow failed: " + e.getCause().getMessage());
            printWorkflowStatus();
        }
    }
...

The following example shows the Workflow interface for the GreetingWorkflow called in the previous example.

...
@WorkflowInterface
public interface GreetingWorkflow {
    @WorkflowMethod
    String greet(Customer customer);

    @SignalMethod
    void setCustomer(Customer customer);

    @QueryMethod
    Customer getCustomer();
...
}

Note that the Signal handler setCustomer is executed before the @WorkflowMethod greet is called.

How to develop with Queries​

A Query is a synchronous operation that is used to get the state of a Workflow Execution.

How to define a Query​

A Query has a name and can have arguments.

  • The name, also called a Query type, is a string.
  • The arguments must be serializable.

To define a Query, define the method name and the result type of the Query.

query(String queryType, Class<R> resultClass, Type resultType, Object... args);

  /* @param queryType name of the Query handler. Usually it is a method name.
   * @param resultClass class of the Query result type
   * @param args optional Query arguments
   * @param <R> type of the Query result
  */

Query methods can take in any number of input parameters which can be used to limit the data that is returned.

Use the Query method names to send and receive Queries.

Query methods must never change any Workflow state including starting Activities or blocking threads in any way.

How to handle a Query​

Queries are handled by your Workflow.

Don’t include any logic that causes Command generation within a Query handler (such as executing Activities). Including such logic causes unexpected behavior.

To handle a Query in the Workflow, create a Query handler using the @QueryMethod annotation in the Workflow interface and define it in the Workflow implementation.

The @QueryMethod annotation indicates that the method is used to handle a Query that is sent to the Workflow Execution. The method can have parameters that can be used to filter data that the Query returns. Because the method returns a value, it must have a return type that is not void.

The Query name defaults to the name of the method. In the following example, the Query name defaults to getStatus.

@WorkflowInterface
public interface FileProcessingWorkflow {
   @QueryMethod
   String getStatus();
}

To overwrite this default naming and assign a custom Query name, use the @QueryMethod annotation with the name parameter. In the following example, the Query name is set to "history".

@WorkflowInterface
public interface FileProcessingWorkflow {
   @QueryMethod(name = "history")
   String getStatus();
}

A Workflow Definition interface can define multiple methods annotated with @QueryMethod, but the method names or the name parameters for each must be unique.

The following Workflow interface has a Query method getCount() to handle Queries to this Workflow.

  @WorkflowInterface
  public interface HelloWorld {
    @WorkflowMethod
    void sayHello(String name);

    @QueryMethod
    int getCount();
  }

The following example is the Workflow implementation with the Query method defined in the HelloWorld Workflow interface from the previous example.

  public static class HelloWorldImpl implements HelloWorld {

    private String greeting = "Hello";
    private int count = 0;

    @Override
    public void sayHello(String name) {
      while (!"Bye".equals(greeting)) {
        logger.info(++count + ": " + greeting + " " + name + "!");
        String oldGreeting = greeting;
        Workflow.await(() -> !Objects.equals(greeting, oldGreeting));
      }
      logger.info(++count + ": " + greeting + " " + name + "!");
    }

    @Override
    public int getCount() {
      return count;
    }
  }

How to send a Query​

Queries are sent from a Temporal Client.

To send a Query to a Workflow Execution from an external process, call the Query method (defined in the Workflow) from a WorkflowStub within the Client code.

For example, the following Client code calls a Query method queryGreeting() defined in the GreetingWorkflow Workflow interface.

 // Create our workflow options
    WorkflowOptions workflowOptions =
        WorkflowOptions.newBuilder()
        .setWorkflowId(WORKFLOW_ID)
        .setTaskQueue(TASK_QUEUE).build();

    // Create the Temporal client stub. It is used to start our workflow execution.
    GreetingWorkflow workflow = client.newWorkflowStub(GreetingWorkflow.class, workflowOptions);

    // Start our workflow asynchronously to not use another thread to query.
    WorkflowClient.start(workflow::createGreeting, "World");

    // Query the Workflow to get the current value of greeting and print it.
    System.out.println(workflow.queryGreeting());

What is a Dynamic Handler?​

Temporal supports Dynamic Workflows, Activities, Signals, and Queries. These are unnamed handlers that are invoked if no other statically defined handler with the given name exists.

Dynamic Handlers provide flexibility to handle cases where the names of Workflows, Activities, Signals, or Queries aren't known at run time.

caution

Dynamic Handlers should be used judiciously as a fallback mechanism rather than the primary approach. Overusing them can lead to maintainability and debugging issues down the line.

Instead, Workflows, Activities, Signals, and Queries should be defined statically whenever possible, with clear names that indicate their purpose. Use static definitions as the primary way of structuring your Workflows.

Reserve Dynamic Handlers for cases where the handler names are not known at compile time and need to be looked up dynamically at runtime. They are meant to handle edge cases and act as a catch-all, not as the main way of invoking logic.

How to set a Dynamic Workflow​

Use DynamicWorkflow to implement Workflow Types dynamically. Register a Workflow implementation type that extends DynamicWorkflow to implement any Workflow Type that is not explicitly registered with the Worker.

The dynamic Workflow interface is implemented with the execute method. This method takes in EncodedValues that are inputs to the Workflow Execution. These inputs can be specified by the Client when invoking the Workflow Execution.

public class MyDynamicWorkflow implements DynamicWorkflow {
   @Override
    public Object execute(EncodedValues args) {
    }
}

How to set a Dynamic Activity​

To handle Activity types that do not have an explicitly registered handler, you can directly implement a dynamic Activity.

Use DynamicActivity to implement any number of Activity types dynamically. When an Activity implementation that extends DynamicActivity is registered, it is called for any Activity type invocation that doesn't have an explicitly registered handler.

The dynamic Activity interface is implemented with the execute method, as shown in the following example.

// Dynamic Activity implementation
 public static class DynamicGreetingActivityImpl implements DynamicActivity {
   @Override
   public Object execute(EncodedValues args) {
     String activityType = Activity.getExecutionContext().getInfo().getActivityType();
     return activityType
         + ": "
         + args.get(0, String.class)
         + " "
         + args.get(1, String.class)
         + " from: "
         + args.get(2, String.class);
   }
 }

Use Activity.getExecutionContext() to get information about the Activity type that should be implemented dynamically.

How to set a Dynamic Signal​

You can also implement Signal handlers dynamically. This is useful for library-level code and implementation of DSLs.

Use Workflow.registerListener(Object) to register an implementation of the DynamicSignalListener in the Workflow implementation code.

Workflow.registerListener(
  (DynamicSignalHandler)
      (signalName, encodedArgs) -> name = encodedArgs.get(0, String.class));

When registered, any Signals sent to the Workflow without a defined handler will be delivered to the DynamicSignalHandler. Note that you can only register one Workflow.registerListener(Object) per Workflow Execution. DynamicSignalHandler can be implemented in both regular and dynamic Workflow implementations.

How to set a Dynamic Query​

You can also implement Query handlers dynamically. This is useful for library-level code and implementation of DSLs.

Use Workflow.registerListener(Object) to register an implementation of the DynamicQueryListener in the Workflow implementation code.

Workflow.registerListener(
  (DynamicQueryHandler)
      (queryName, encodedArgs) -> name = encodedArgs.get(0, String.class));

When registered, any Queries sent to the Workflow without a defined handler will be delivered to the DynamicQueryHandler. Note that you can only register one Workflow.registerListener(Object) per Workflow Execution. DynamicQueryHandler can be implemented in both regular and dynamic Workflow implementations.

How to develop with Updates​

An Update is an operation that can mutate the state of a Workflow Execution and return a response.

How to define Updates​

An Update handler has a name, arguments, response, and an optional validator.

  • The name, also called an Update type, is a string.
  • The arguments and response must be serializable.

The @UpdateMethod annotation indicates that the method is used to handle and respond to update requests.

@UpdateMethod
   String myUpdate(String signalName);

How to handle Updates in an Workflow​

Workflows listen for Update by the update's name.

Use the @UpdateMethod annotation to handle Updates in the Workflow interface. The handler method can accept multiple serializable input parameters, but it's recommend using only a single parameter. The function can return a serializable value or void. If any exception is throw while handling an update that exception may fail the Workflow task or the update depending on the type of the exception and WorkflowImplementationOptions.setFailWorkflowExceptionTypes

@WorkflowInterface
public interface FileProcessingWorkflow {

   @WorkflowMethod
   String processFile(Arguments args);

   @UpdateMethod
   void pauseProcessing();
}

Update handlers, unlike Query handlers, can change Workflow state.

The Updates type defaults to the name of the method. To overwrite this default naming and assign a custom Update type, use the @UpdateMethod annotation with the name parameter.

@WorkflowInterface
public interface FileProcessingWorkflow {

   @WorkflowMethod
   String processFile(Arguments args);

   @UpdateMethod(name = "pause")
   void pauseProcessing();
}

Dynamic Update Handler

You can also implement Update handlers dynamically. This is useful for library-level code and implementation of DSLs.

Workflow.registerListener(
  (DynamicUpdateHandler)
      (updateName, encodedArgs) -> encodedArgs.get(0, String.class));

When registered, any Updates sent to the Workflow without a defined handler will be delivered to the DynamicUpdateHandler. You can only register one Workflow.registerListener(Object) per Workflow Execution. DynamicUpdateHandler can be implemented in both regular and dynamic Workflow implementations.

How to validate an Update in a Workflow​

Validate certain aspects of the data sent to the Workflow using an Update Validator method. For instance, a counter Workflow might never want to accept a non-positive number. Use the @UpdateValidatorMethod annotation and set updateName to the name of your Update handler. Your Update Validator should accept the same input parameters as your Update Handler and return void.

@WorkflowInterface
public interface GreetingWorkflow {
    @WorkflowMethod
    List<String> getGreetings();

    @UpdateMethod
    int addGreeting(String name);

    @UpdateValidatorMethod(updateName = "addGreeting")
    void addGreetingValidator(String name);
}

How to send an Update from a Client​

To send an Update to a Workflow Execution from a Client, call the Update method, annotated with @UpdateMethod in the Workflow interface, from the Client code.

In the following Client code example, start the Workflow getGreetings and call the Update method addGreeting that is handled in the Workflow.

WorkflowOptions workflowOptions =
    WorkflowOptions.newBuilder().setTaskQueue(TASK_QUEUE).setWorkflowId(WORKFLOW_ID).build();

// Create a typed Workflow stub for GreetingsWorkflow
GreetingWorkflow workflow = client.newWorkflowStub(GreetingWorkflow.class, workflowOptions);

// Start the Workflow
WorkflowClient.start(workflow::getGreetings);

// Send an update to the Workflow. addGreeting returns
// the number of greetings our workflow has received.
int count = workflow.addGreeting("World");

Workflow timeouts​

Each Workflow timeout controls the maximum duration of a different aspect of a Workflow Execution.

Workflow timeouts are set when starting the Workflow Execution.

Create an instance of WorkflowStub in the Client code and set your timeout.

Available timeouts are:

//create Workflow stub for YourWorkflowInterface
YourWorkflowInterface workflow1 =
    WorkerGreet.greetclient.newWorkflowStub(
        GreetWorkflowInterface.class,
        WorkflowOptions.newBuilder()
                .setWorkflowId("YourWorkflow")
                .setTaskQueue(WorkerGreet.TASK_QUEUE)
                // Set Workflow Timeout duration
                .setWorkflowExecutionTimeout(Duration.ofSeconds(10))
                // .setWorkflowRunTimeout(Duration.ofSeconds(10))
                // .setWorkflowTaskTimeout(Duration.ofSeconds(10))
                .build());

Workflow retries​

A Retry Policy can work in cooperation with the timeouts to provide fine controls to optimize the execution experience.

Use a Retry Policy to retry a Workflow Execution in the event of a failure.

Workflow Executions do not retry by default, and Retry Policies should be used with Workflow Executions only in certain situations.

To set a Workflow Retry Options in the WorkflowStub instance use WorkflowOptions.Builder.setWorkflowRetryOptions.

  • Type: RetryOptions
  • Default: Null which means no retries will be attempted.
//create Workflow stub for GreetWorkflowInterface
GreetWorkflowInterface workflow1 =
    WorkerGreet.greetclient.newWorkflowStub(
        GreetWorkflowInterface.class,
        WorkflowOptions.newBuilder()
                .setWorkflowId("GreetWF")
                .setTaskQueue(WorkerGreet.TASK_QUEUE)
                // Set Workflow Retry Options
                .setRetryOptions(RetryOptions.newBuilder()
                .build());

How to set Activity timeouts​

Each Activity timeout controls the maximum duration of a different aspect of an Activity Execution.

The following timeouts are available in the Activity Options.

An Activity Execution must have either the Start-To-Close or the Schedule-To-Close Timeout set.

Set your Activity Timeout from the ActivityOptions.Builder class.

Available timeouts are:

  • ScheduleToCloseTimeout()
  • ScheduleToStartTimeout()
  • StartToCloseTimeout()

You can set Activity Options using an ActivityStub within a Workflow implementation, or per-Activity using WorkflowImplementationOptions within a Worker.

The following uses ActivityStub.

GreetingActivities activities = Workflow.newActivityStub(GreetingActivities.class,
                ActivityOptions.newBuilder()
                        .setScheduleToCloseTimeout(Duration.ofSeconds(5))
                        // .setStartToCloseTimeout(Duration.ofSeconds(2)
                        // .setScheduletoCloseTimeout(Duration.ofSeconds(20))
                        .build());

The following uses WorkflowImplementationOptions.

WorkflowImplementationOptions options =
            WorkflowImplementationOptions.newBuilder()
                    .setActivityOptions(
                            ImmutableMap.of(
                                    "GetCustomerGreeting",
                                    // Set Activity Execution timeout
                                    ActivityOptions.newBuilder()
                                        .setScheduleToCloseTimeout(Duration.ofSeconds(5))
                                        // .setStartToCloseTimeout(Duration.ofSeconds(2))
                                        // .setScheduleToStartTimeout(Duration.ofSeconds(5))
                                        .build()))
                    .build();
note

If you define options per-Activity Type options with WorkflowImplementationOptions.setActivityOptions(), setting them again specifically with ActivityStub in a Workflow will override this setting.

How to set an Activity Retry Policy​

A Retry Policy works in cooperation with the timeouts to provide fine controls to optimize the execution experience.

Activity Executions are automatically associated with a default Retry Policy if a custom one is not provided.

To set a Retry Policy, known as the Retry Options in Java, use ActivityOptions.newBuilder.setRetryOptions().

  • Type: RetryOptions

  • Default: Server-defined Activity Retry policy.

  • With ActivityStub

    private final ActivityOptions options =
        ActivityOptions.newBuilder()
            // note that either StartToCloseTimeout or ScheduleToCloseTimeout are
            // required when setting Activity options.
            .setStartToCloseTimeout(Duration.ofSeconds(5))
            .setRetryOptions(
                RetryOptions.newBuilder()
                    .setInitialInterval(Duration.ofSeconds(1))
                    .setMaximumInterval(Duration.ofSeconds(10))
                    .build())
            .build();

  • With WorkflowImplementationOptions

    WorkflowImplementationOptions options =
            WorkflowImplementationOptions.newBuilder()
                   .setActivityOptions(
                        ImmutableMap.of(
                            "EmailCustomerGreeting",
                            ActivityOptions.newBuilder()
                                  // note that either StartToCloseTimeout or ScheduleToCloseTimeout are
                                  // required when setting Activity options.
                                  .setStartToCloseTimeout(Duration.ofSeconds(5))
                                  .setRetryOptions(
                                        RetryOptions.newBuilder()
                                            .setDoNotRetry(NullPointerException.class.getName())
                                            .build())
                                  .build()))
                  .build();

How to Heartbeat an Activity​

An Activity Heartbeat is a ping from the Worker Process that is executing the Activity to the Temporal Cluster. Each Heartbeat informs the Temporal Cluster that the Activity Execution is making progress and the Worker has not crashed. If the Cluster does not receive a Heartbeat within a Heartbeat Timeout time period, the Activity will be considered failed and another Activity Task Execution may be scheduled according to the Retry Policy.

Heartbeats may not always be sent to the Cluster—they may be throttled by the Worker.

Activity Cancellations are delivered to Activities from the Cluster when they Heartbeat. Activities that don't Heartbeat can't receive a Cancellation. Heartbeat throttling may lead to Cancellation getting delivered later than expected.

Heartbeats can contain a details field describing the Activity's current progress. If an Activity gets retried, the Activity can access the details from the last Heartbeat that was sent to the Cluster.

To Heartbeat an Activity Execution in Java, use the Activity.getExecutionContext().heartbeat() Class method.

public class YourActivityDefinitionImpl implements YourActivityDefinition {

  @Override
  public String yourActivityMethod(YourActivityMethodParam param) {
    // ...
    Activity.getExecutionContext().heartbeat(details);
    // ...
  }
  // ...
}

The method takes an optional argument, the details variable above that represents latest progress of the Activity Execution. This method can take a variety of types such as an exception object, custom object, or string.

If the Activity Execution times out, the last Heartbeat details are included in the thrown ActivityTimeoutException, which can be caught by the calling Workflow. The Workflow can then use the details information to pass to the next Activity invocation if needed.

In the case of Activity retries, the last Heartbeat's details are available and can be extracted from the last failed attempt by using Activity.getExecutionContext().getHeartbeatDetails(Class<V> detailsClass)

How to set a Heartbeat Timeout​

A Heartbeat Timeout works in conjunction with Activity Heartbeats.

To set a Heartbeat Timeout, use ActivityOptions.newBuilder.setHeartbeatTimeout.

  • Type: Duration
  • Default: None

You can set Activity Options using an ActivityStub within a Workflow implementation, or per-Activity using WorkflowImplementationOptions within a Worker. Note that if you define options per-Activity Type options with WorkflowImplementationOptions.setActivityOptions(), setting them again specifically with ActivityStub in a Workflow will override this setting.

  • With ActivityStub

    private final GreetingActivities activities =
        Workflow.newActivityStub(
            GreetingActivities.class,
            ActivityOptions.newBuilder()
                // note that either StartToCloseTimeout or ScheduleToCloseTimeout are
                // required when setting Activity options.
                .setStartToCloseTimeout(Duration.ofSeconds(5))
                .setHeartbeatTimeout(Duration.ofSeconds(2))
                .build());

  • With WorkflowImplementationOptions

    WorkflowImplementationOptions options =
                WorkflowImplementationOptions.newBuilder()
                        .setActivityOptions(
                                ImmutableMap.of(
                                  "EmailCustomerGreeting",
                                        ActivityOptions.newBuilder()
                                            // note that either StartToCloseTimeout or ScheduleToCloseTimeout are
                                            // required when setting Activity options.
                                              .setStartToCloseTimeout(Duration.ofSeconds(5))
                                              .setHeartbeatTimeout(Duration.ofSeconds(2))
                                              .build()))
                        .build();

How to asynchronously complete an Activity​

Asynchronous Activity Completion enables the Activity Function to return without the Activity Execution completing.

There are three steps to follow:

  1. The Activity provides the external system with identifying information needed to complete the Activity Execution. Identifying information can be a Task Token, or a combination of Namespace, Workflow Id, and Activity Id.
  2. The Activity Function completes in a way that identifies it as waiting to be completed by an external system.
  3. The Temporal Client is used to Heartbeat and complete the Activity.

To complete an Activity asynchronously, set the ActivityCompletionClient interface to the complete() method.

    @Override
    public String composeGreeting(String greeting, String name) {

      // Get the activity execution context
      ActivityExecutionContext context = Activity.getExecutionContext();

      // Set a correlation token that can be used to complete the activity asynchronously
      byte[] taskToken = context.getTaskToken();

      /**
       * For the example we will use a {@link java.util.concurrent.ForkJoinPool} to execute our
       * activity. In real-life applications this could be any service. The composeGreetingAsync
       * method is the one that will actually complete workflow action execution.
       */
      ForkJoinPool.commonPool().execute(() -> composeGreetingAsync(taskToken, greeting, name));
      context.doNotCompleteOnReturn();

      // Since we have set doNotCompleteOnReturn(), the workflow action method return value is
      // ignored.
      return "ignored";
    }

    // Method that will complete action execution using the defined ActivityCompletionClient
    private void composeGreetingAsync(byte[] taskToken, String greeting, String name) {
      String result = greeting + " " + name + "!";

      // Complete our workflow activity using ActivityCompletionClient
      completionClient.complete(taskToken, result);
    }
  }

Alternatively, set the doNotCompleteOnReturn() method during an Activity Execution.

    @Override
    public String composeGreeting(String greeting, String name) {

      // Get the activity execution context
      ActivityExecutionContext context = Activity.getExecutionContext();

      // Set a correlation token that can be used to complete the activity asynchronously
      byte[] taskToken = context.getTaskToken();

      /**
       * For the example we will use a {@link java.util.concurrent.ForkJoinPool} to execute our
       * activity. In real-life applications this could be any service. The composeGreetingAsync
       * method is the one that will actually complete workflow action execution.
       */
      ForkJoinPool.commonPool().execute(() -> composeGreetingAsync(taskToken, greeting, name));
      context.doNotCompleteOnReturn();

      // Since we have set doNotCompleteOnReturn(), the workflow action method return value is
      // ignored.
      return "ignored";
    }

When this method is called during an Activity Execution, the Activity Execution does not complete when its method returns.

How to start a Child Workflow Execution​

A Child Workflow Execution is a Workflow Execution that is scheduled from within another Workflow using a Child Workflow API.

When using a Child Workflow API, Child Workflow related Events (StartChildWorkflowExecutionInitiated, ChildWorkflowExecutionStarted, ChildWorkflowExecutionCompleted, etc...) are logged in the Workflow Execution Event History.

Always block progress until the ChildWorkflowExecutionStarted Event is logged to the Event History to ensure the Child Workflow Execution has started. After that, Child Workflow Executions may be abandoned using the default Abandon Parent Close Policy set in the Child Workflow Options.

To be sure that the Child Workflow Execution has started, first call the Child Workflow Execution method on the instance of Child Workflow future, which returns a different future.

Then get the value of an object that acts as a proxy for a result that is initially unknown, which is what waits until the Child Workflow Execution has spawned.

The first call to the Child Workflow stub must always be its Workflow method (method annotated with @WorkflowMethod). Similar to Activities, invoking Child Workflow methods can be made synchronous or asynchronous by using Async#function or Async#procedure. The synchronous call blocks until a Child Workflow method completes. The asynchronous call returns a Promise which can be used to wait for the completion of the Child Workflow method, as in the following example:

GreetingChild child = Workflow.newChildWorkflowStub(GreetingChild.class);
Promise<String> greeting = Async.function(child::composeGreeting, "Hello", name);
// ...
greeting.get()

To execute an untyped Child Workflow asynchronously, call executeAsync on the ChildWorkflowStub, as shown in the following example.

//...
ChildWorkflowStub childUntyped =
    Workflow.newUntypedChildWorkflowStub(
        "GreetingChild", // your workflow type
        ChildWorkflowOptions.newBuilder().setWorkflowId("childWorkflow").build());

Promise<String> greeting =
    childUntyped.executeAsync(String.class, String.class, "Hello", name);
String result = greeting.get();
//...

The following examples show how to spawn a Child Workflow:

  • Spawn a Child Workflow from a Workflow:

    // Child Workflow interface
    @WorkflowInterface
    public interface GreetingChild {
    @WorkflowMethod
    String composeGreeting(String greeting, String name);
    }
    // Child Workflow implementation not shown

    // Parent Workflow implementation
    public class GreetingWorkflowImpl implements GreetingWorkflow {

    @Override
    public String getGreeting(String name) {
        GreetingChild child = Workflow.newChildWorkflowStub(GreetingChild.class);

        // This is a blocking call that returns only after child has completed.
        return child.composeGreeting("Hello", name );
    }
    }

  • Spawn two Child Workflows (with the same type) in parallel:

    // Parent Workflow implementation
    public class GreetingWorkflowImpl implements GreetingWorkflow {

        @Override
        public String getGreeting(String name) {

            // Workflows are stateful, so a new stub must be created for each new child.
            GreetingChild child1 = Workflow.newChildWorkflowStub(GreetingChild.class);
            Promise<String> greeting1 = Async.function(child1::composeGreeting, "Hello", name);

            // Both children will run concurrently.
            GreetingChild child2 = Workflow.newChildWorkflowStub(GreetingChild.class);
            Promise<String> greeting2 = Async.function(child2::composeGreeting, "Bye", name);

            // Do something else here.
            ...
            return "First: " + greeting1.get() + ", second: " + greeting2.get();
        }
    }

  • Send a Signal to a Child Workflow from the parent:

    // Child Workflow interface
    @WorkflowInterface
    public interface GreetingChild {
        @WorkflowMethod
        String composeGreeting(String greeting, String name);

        @SignalMethod
        void updateName(String name);
    }

    // Parent Workflow implementation
    public class GreetingWorkflowImpl implements GreetingWorkflow {

        @Override
        public String getGreeting(String name) {
            GreetingChild child = Workflow.newChildWorkflowStub(GreetingChild.class);
            Promise<String> greeting = Async.function(child::composeGreeting, "Hello", name);
            child.updateName("Temporal");
            return greeting.get();
        }
    }

  • Sending a Query to Child Workflows from within the parent Workflow code is not supported. However, you can send a Query to Child Workflows from Activities using WorkflowClient.

Related reads:

How to set a Parent Close Policy​

A Parent Close Policy determines what happens to a Child Workflow Execution if its Parent changes to a Closed status (Completed, Failed, or Timed Out).

The default Parent Close Policy option is set to terminate the Child Workflow Execution.

Set Parent Close Policy on an instance of ChildWorkflowOptions using ChildWorkflowOptions.newBuilder().setParentClosePolicy.

  • Type: ChildWorkflowOptions.Builder
  • Default: PARENT_CLOSE_POLICY_TERMINATE
 public void parentWorkflow() {
     ChildWorkflowOptions options =
        ChildWorkflowOptions.newBuilder()
            .setParentClosePolicy(ParentClosePolicy.PARENT_CLOSE_POLICY_ABANDON)
            .build();
     MyChildWorkflow child = Workflow.newChildWorkflowStub(MyChildWorkflow.class, options);
     Async.procedure(child::<workflowMethod>, <args>...);
     Promise<WorkflowExecution> childExecution = Workflow.getWorkflowExecution(child);
     // Wait for child to start
     childExecution.get()
}

In this example, we are:

  1. Setting ChildWorkflowOptions.ParentClosePolicy to ABANDON when creating a Child Workflow stub.
  2. Starting Child Workflow Execution asynchronously using Async.function or Async.procedure.
  3. Calling Workflow.getWorkflowExecution(…) on the child stub.
  4. Waiting for the Promise returned by getWorkflowExecution to complete. This indicates whether the Child Workflow started successfully (or failed).
  5. Completing parent Workflow Execution asynchronously.

Steps 3 and 4 are needed to ensure that a Child Workflow Execution starts before the parent closes. If the parent initiates a Child Workflow Execution and then completes immediately after, the Child Workflow will never execute.

How to Continue-As-New​

Continue-As-New enables a Workflow Execution to close successfully and create a new Workflow Execution in a single atomic operation if the number of Events in the Event History is becoming too large. The Workflow Execution spawned from the use of Continue-As-New has the same Workflow Id, a new Run Id, and a fresh Event History and is passed all the appropriate parameters.

Temporal SDK allows you to use Continue-As-New in various ways.

To continue execution of the same Workflow that is currently running, use:

Workflow.continueAsNew(input1, ...);

To continue execution of a currently running Workflow as a completely different Workflow Type, use Workflow.newContinueAsNewStub(). For example, in a Workflow class called YourWorkflow, we can create a Workflow stub with a different type, and call its Workflow method to continue execution as that type:

MyOtherWorkflow continueAsNew = Workflow.newContinueAsNewStub(MyOtherWorkflow.class);
coninueAsNew.greet(input);

To provide ContinueAsNewOptions options in Workflow.newContinueAsNewStub() use:

ContinueAsNewOptions options = ContinueAsNewOptions.newBuilder()
        .setTaskQueue("newTaskQueueName")
        .build();

MyOtherWorkflow continueAsNew = Workflow.newContinueAsNewStub(MyOtherWorkflow.class, options);
// ...
continueAsNew.greet(input);

Providing these options allows you to continue Workflow Execution as a new Workflow run, with a different Workflow Type, and on a different Task Queue.

Java Workflow reference: https://www.javadoc.io/doc/io.temporal/temporal-sdk/latest/io/temporal/workflow/package-summary.html

What is a Timer?​

A Workflow can set a durable timer for a fixed time period. In some SDKs, the function is called sleep(), and in others, it's called timer().

A Workflow can sleep for months. Timers are persisted, so even if your Worker or Temporal Cluster is down when the time period completes, as soon as your Worker and Cluster are back up, the Workflow.sleep() call resolves and your code continues executing.

Sleeping is a resource-light operation: it does not tie up the process, and you can run millions of Timers off a single Worker.

To set a Timer in Java, use sleep() and pass the number of seconds you want to wait before continuing.

sleep(5);

How to Schedule a Workflow​

Scheduling Workflows is a crucial aspect of any automation process, especially when dealing with time-sensitive tasks. By scheduling a Workflow, you can automate repetitive tasks, reduce the need for manual intervention, and ensure timely execution of your business processes

Use any of the following action to help Schedule a Workflow Execution and take control over your automation process.

How to create a Schedule in Java​

The create action enables you to create a new Schedule. When you create a new Schedule, a unique Schedule ID is generated, which you can use to reference the Schedule in other Schedule commands.

To create a Scheduled Workflow Execution in Java, use the createSchedule() method on the ScheduleClient. Schedules must be initialized with a Schedule ID,

Schedule schedule =
    Schedule.newBuilder()
        .setAction(
            ScheduleActionStartWorkflow.newBuilder()
                .setWorkflowType(HelloSchedules.GreetingWorkflow.class)
                .setArguments("World")
                .setOptions(
                    WorkflowOptions.newBuilder()
                        .setWorkflowId("WorkflowId")
                        .setTaskQueue("TaskQueue")
                        .build())
                .build())
        .setSpec(ScheduleSpec.newBuilder().build())
        .build();

// Create a schedule on the server
ScheduleHandle handle =
    scheduleClient.createSchedule("ScheduleId", schedule, ScheduleOptions.newBuilder().build());

How to backfill a Schedule in Java​

The backfill action executes Actions ahead of their specified time range. This command is useful when you need to execute a missed or delayed Action, or when you want to test the Workflow before its scheduled time.

To Backfill a Scheduled Workflow Execution in Java, use the backfill() method on the ScheduleHandle.

ScheduleHandle handle = client.getHandle("schedule-id")

Instant now = Instant.now();
handle.backfill(
    Arrays.asList(
        new ScheduleBackfill(now.minusMillis(5500), now.minusMillis(2500)),
        new ScheduleBackfill(now.minusMillis(2500), now)));

How to delete a Schedule in Java​

The delete action enables you to delete a Schedule. When you delete a Schedule, it does not affect any Workflows that were started by the Schedule.

To delete a Scheduled Workflow Execution in Java, use the delete() method on the Schedule Handle.

ScheduleHandle handle = client.getHandle("schedule-id")
handle.delete();

How to describe a Schedule in Java​

The describe action shows the current Schedule configuration, including information about past, current, and future Workflow Runs. This command is helpful when you want to get a detailed view of the Schedule and its associated Workflow Runs.

To describe a Scheduled Workflow Execution in Java, use the describe() method on the ScheduleHandle.

ScheduleHandle handle = client.getHandle("schedule-id")
ScheduleDescription description = handle.describe();

How to describe a Schedule in Java​

The list action lists all the available Schedules. This command is useful when you want to view a list of all the Schedules and their respective Schedule IDs.

To list all schedules, use the listSchedules() asynchronous method on the ScheduleClient. If a schedule is added or deleted, it may not be available in the list immediately.

Stream<ScheduleListDescription> scheduleStream = client.listSchedules();

How to pause a Schedule in Java​

The pause action enables you to pause and unpause a Schedule. When you pause a Schedule, all the future Workflow Runs associated with the Schedule are temporarily stopped. This command is useful when you want to temporarily halt a Workflow due to maintenance or any other reason.

To pause a Scheduled Workflow Execution in Java, use the pause() method on the ScheduleHandle. You can pass a note to the pause() method to provide a reason for pausing the schedule.

ScheduleHandle handle = client.getHandle("schedule-id")
handle.pause("Pausing the schedule for now");

How to trigger a Schedule in Java​

The trigger action triggers an immediate action with a given Schedule. By default, this action is subject to the Overlap Policy of the Schedule. This command is helpful when you want to execute a Workflow outside of its scheduled time.

To trigger a Scheduled Workflow Execution in Java, use the trigger() method on the ScheduleHandle.

ScheduleHandle handle = client.getHandle("schedule-id")
handle.trigger();

How to update a Schedule in Java​

The update action enables you to update an existing Schedule. This command is useful when you need to modify the Schedule's configuration, such as changing the start time, end time, or interval.

Create a function that takes ScheduleUpdateInput and returns ScheduleUpdate. To update a Schedule, use a callback to build the update from the description. The following example updates the Schedule to set a limited number of actions.

ScheduleHandle handle = client.getHandle("schedule-id")
handle.update(
    (ScheduleUpdateInput input) -> {
      Schedule.Builder builder = Schedule.newBuilder(input.getDescription().getSchedule());
      // Make the schedule paused to demonstrate how to unpause a schedule
      builder.setState(
          ScheduleState.newBuilder()
              .setLimitedAction(true)
              .setRemainingActions(10)
              .build());
      return new ScheduleUpdate(builder.build());
    });

How to set a Cron Schedule in Java​

A Temporal Cron Job is the series of Workflow Executions that occur when a Cron Schedule is provided in the call to spawn a Workflow Execution.

A Cron Schedule is provided as an option when the call to spawn a Workflow Execution is made.

Set the Cron Schedule with the WorkflowStub instance in the Client code using WorkflowOptions.Builder.setCronSchedule.

Setting setCronSchedule changes the Workflow Execution into a Temporal Cron Job. The default timezone for a Cron is UTC.

  • Type: String
  • Default: None
//create Workflow stub for YourWorkflowInterface
YourWorkflowInterface workflow1 =
    YourWorker.yourclient.newWorkflowStub(
        YourWorkflowInterface.class,
        WorkflowOptions.newBuilder()
                .setWorkflowId("YourWF")
                .setTaskQueue(YourWorker.TASK_QUEUE)
                // Set Cron Schedule
                .setCronSchedule("* * * * *")
                .build());

For more details, see the Cron Sample

Side Effects​

Side Effects are used to execute non-deterministic code, such as generating a UUID or a random number, without compromising deterministic in the Workflow. This is done by storing the non-deterministic results of the Side Effect into the Workflow Event History.

A Side Effect does not re-execute during a Replay. Instead, it returns the recorded result from the Workflow Execution Event History.

Side Effects should not fail. An exception that is thrown from the Side Effect causes failure and retry of the current Workflow Task.

An Activity or a Local Activity may also be used instead of a Side effect, as its result is also persisted in Workflow Execution History.

note

You shouldn’t modify the Workflow state inside a Side Effect function, because it is not reexecuted during Replay. Side Effect function should be used to return a value.

To use a Side Effect in Java, set the sideEffect() function in your Workflow Execution and return the non-deterministic code.

int random = Workflow.sideEffect(Integer.class, () -> random.nextInt(100));
if random < 50 {
       ....
} else {
       ....
}

Here's another example that uses sideEffect().

// implementation of the @WorkflowMethod
public void execute() {
    int randomInt = Workflow.sideEffect( int.class, () -> {
        Random random = new SecureRandom();
        return random.nextInt();
    });

    String userHome = Workflow.sideEffect(String.class, () -> System.getenv("USER_HOME"));

    if(randomInt % 2 == 0) {
        // ...
    } else {
        // ...
    }
}

Java also provides a deterministic method to generate random numbers or random UUIDs.

To generate random numbers in a deterministic method, use newRandom()

// implementation of the @WorkflowMethod
public void execute() {
    int randomInt = Workflow.newRandom().nextInt();
    // ...
}

To generate a random UUID in a deterministic method, use randomUUID().

// implementation of the @WorkflowMethod
public void execute() {
    String randomUUID = Workflow.randomUUID().toString();
    // ...
}

How to create and manage Namespaces​

You can create, update, deprecate or delete your Namespaces using either the Temporal CLI or SDK APIs.

Use Namespaces to isolate your Workflow Executions according to your needs. For example, you can use Namespaces to match the development lifecycle by having separate dev and prod Namespaces. You could also use them to ensure Workflow Executions between different teams never communicate - such as ensuring that the teamA Namespace never impacts the teamB Namespace.

On Temporal Cloud, use the Temporal Cloud UI to create and manage a Namespace from the UI, or tcld commands to manage Namespaces from the command-line interface.

On self-hosted Temporal Cluster, you can register and manage your Namespaces using the Temporal CLI (recommended) or programmatically using APIs. Note that these APIs and Temporal CLI commands will not work with Temporal Cloud.

Use a custom Authorizer on your Frontend Service in the Temporal Cluster to set restrictions on who can create, update, or deprecate Namespaces.

You must register a Namespace with the Temporal Cluster before setting it in the Temporal Client.

How to register Namespaces​

Registering a Namespace creates a Namespace on the Temporal Cluster or Temporal Cloud.

On Temporal Cloud, use the Temporal Cloud UI or tcld commands to create Namespaces.

On self-hosted Temporal Cluster, you can register your Namespaces using the Temporal CLI (recommended) or programmatically using APIs. Note that these APIs and Temporal CLI commands will not work with Temporal Cloud.

Use a custom Authorizer on your Frontend Service in the Temporal Cluster to set restrictions on who can create, update, or deprecate Namespaces.

Use the RegisterNamespace API to register a Namespace and set the Retention Period for the Workflow Execution Event History for the Namespace.

//...
import com.google.protobuf.util.Durations;
import io.temporal.api.workflowservice.v1.RegisterNamespaceRequest;
//...
public static void createNamespace(String name) {
    RegisterNamespaceRequest req = RegisterNamespaceRequest.newBuilder()
            .setNamespace("your-custom-namespace")
            .setWorkflowExecutionRetentionPeriod(Durations.fromDays(3)) // keeps the Workflow Execution
            //Event History for up to 3 days in the Persistence store. Not setting this value will throw an error.
            .build();
    service.blockingStub().registerNamespace(req);
}
//...

The Retention Period setting using WorkflowExecutionRetentionPeriod is mandatory. The minimum value you can set for this period is 1 day.

Once registered, set Namespace using WorkflowClientOptions within a Workflow Client to run your Workflow Executions within that Namespace. See how to set Namespace in a Client in Java for details.

Note that Namespace registration using this API takes up to 10 seconds to complete. Ensure that you wait for this registration to complete before starting the Workflow Execution against the Namespace.

To update your Namespace use the UpdateNamespace API with the NamespaceClient.

How to manage Namespaces​

You can get details for your Namespaces, update Namespace configuration, and deprecate or delete your Namespaces.

On Temporal Cloud, use the Temporal Cloud UI or tcld commands to manage Namespaces.

On self-hosted Temporal Cluster, you can manage your registered Namespaces using the Temporal CLI (recommended) or programmatically using APIs. Note that these APIs and Temporal CLI commands will not work with Temporal Cloud.

Use a custom Authorizer on your Frontend Service in the Temporal Cluster to set restrictions on who can create, update, or deprecate Namespaces.

You must register a Namespace with the Temporal Cluster before setting it in the Temporal Client.

On Temporal Cloud, use the Temporal Cloud UI or tcld commands to manage Namespaces.

On self-hosted Temporal Cluster, you can manage your registered Namespaces using the Temporal CLI (recommended) or programmatically using APIs. Note that these APIs and Temporal CLI commands will not work with Temporal Cloud.

  • Update information and configuration for a registered Namespace on your Temporal Cluster:

    import io.temporal.api.workflowservice.v1.*;
    //...
    UpdateNamespaceRequest updateNamespaceRequest = UpdateNamespaceRequest.newBuilder()
                .setNamespace("your-namespace-name") //the namespace that you want to update
                .setUpdateInfo(UpdateNamespaceInfo.newBuilder() //has options to update namespace info
                        .setDescription("your updated namespace description") //updates description in the namespace info.
                        .build())
                .setConfig(NamespaceConfig.newBuilder() //has options to update namespace configuration
                        .setWorkflowExecutionRetentionTtl(Durations.fromHours(30)) //updates the retention period for the namespace "your-namespace--name" to 30 hrs.
                        .build())
                .build();
        UpdateNamespaceResponse updateNamespaceResponse = namespaceservice.blockingStub().updateNamespace(updateNamespaceRequest);
    //...

  • Get details for a registered Namespace on your Temporal Cluster:

    import io.temporal.api.workflowservice.v1.*;
    //...
    DescribeNamespaceRequest descNamespace = DescribeNamespaceRequest.newBuilder()
                .setNamespace("your-namespace-name") //specify the namespace you want details for
                .build();
        DescribeNamespaceResponse describeNamespaceResponse = namespaceservice.blockingStub().describeNamespace(descNamespace);
        System.out.println("Namespace Description: " + describeNamespaceResponse);
    //...

  • Get details for all registered Namespaces on your Temporal Cluster:

    import io.temporal.api.workflowservice.v1.*;
    //...
    ListNamespacesRequest listNamespaces = ListNamespacesRequest.newBuilder().build();
        ListNamespacesResponse listNamespacesResponse = namespaceservice.blockingStub().listNamespaces(listNamespaces); //lists 1-100 namespaces (1 page) in the active cluster. To list all, set the page size or loop until NextPageToken is nil.
    //...

  • Deprecate a Namespace: The DeprecateNamespace API updates the state of a registered Namespace to "DEPRECATED". Once a Namespace is deprecated, you cannot start new Workflow Executions on it. All existing and running Workflow Executions on a deprecated Namespace will continue to run. Example:

    import io.temporal.api.workflowservice.v1.*;
    //...
    DeprecateNamespaceRequest deprecateNamespace = DeprecateNamespaceRequest.newBuilder()
                .setNamespace("your-namespace-name") //specify the namespace that you want to deprecate
                .build();
        DeprecateNamespaceResponse response = namespaceservice.blockingStub().deprecateNamespace(deprecateNamespace);
    //...

  • Delete a Namespace: The DeleteNamespace API deletes a Namespace. Deleting a Namespace deletes all running and completed Workflow Executions on the Namespace, and removes them from the persistence store and the visibility store.

    Example:

    //...
    DeleteNamespaceResponse res =
    OperatorServiceStubs.newServiceStubs(OperatorServiceStubsOptions.newBuilder()
            .setChannel(service.getRawChannel())
            .validateAndBuildWithDefaults())
        .blockingStub()
        .deleteNamespace(DeleteNamespaceRequest.newBuilder().setNamespace("your-namespace-name").build());
    //...