Start New Workflows

Asynchronous dispatch

The asynchronous dispatch of a new workflow starts a new instance without waiting for its completion:

We can start a new workflow using this stub:

// Stub of a new HelloWorld workflow
HelloWorldWorkflow w = client.newWorkflow(HelloWorldWorkflow.class);

// synchronous dispatch of a new workflow
Deferred<String> deferred = client.dispatch(w::greet, "Infinitic");

// Stub of a new HelloWorld workflow
val w : HelloWorldWorkflow = client.newWorkflow(HelloWorldWorkflow::class.java)

// asynchronous dispatch of a new workflow
val deferred : Deferred<String> = client.dispatch(w::greet, "Infinitic") }

The dispatch method returns when the ad-hoc message has been received by Pulsar. If we do not want to wait for this, we can use dispatchAsync instead:

CompletableFuture<Deferred<String>> future = 
    client.dispatchAsync(w::greet, "Infinitic");

val future: CompletableFuture<Deferred<String>> = 
    client.dispatchAsync(w::greet, "Infinitic") }

This CompletableFuture returns when the ad-hoc message has been received by Pulsar.

The Deferred<T> object can be used to:

• retrieve the underlying workflow's id:

• wait for the synchronous completion:

  where T is the actual return type.

  The await() method blocks the current thread of the client - up to the workflow termination. It will throw an UnknownWorkflowException if the workflow is already terminated.

Synchronous dispatch

The synchronous dispatch of a new workflow starts a new instance and waits for its completion:

We can dispatch a workflow and wait for its completion synchronously using the stub of a new workflow:

// Stub of a new HelloWorld workflow
HelloWorldWorkflow w = client.newWorkflow(HelloWorldWorkflow.class);

// synchronous dispatch of a new workflow
String greeting = w.greet("Infinitic");

// Stub of a new HelloWorld workflow
val w : HelloWorldWorkflow = client.newWorkflow(HelloWorldWorkflow::class.java)

// synchronous dispatch of a new workflow
val greeting = w.greet("Infinitic")

When dispatching a workflow, the client serializes parameters and sends them through Pulsar to the [workflow worker, which will orchestrate the workflow. Eventually, the return value will be serialized and sent back to the client through Pulsar.