Versioning

The Temporal Platform requires that Workflow code is deterministic. Because of that requirement, the Temporal Java SDK offers two dedicated versioning features.

How to patch Workflows in Java

Use the Workflow.getVersion function to return a version of the code that should be executed and then use the returned value to pick a correct branch. Let's look at an example.

public void processFile(Arguments args) {
    String localName = null;
    String processedName = null;
    try {
        localName = activities.download(args.getSourceBucketName(), args.getSourceFilename());
        processedName = activities.processFile(localName);
        activities.upload(args.getTargetBucketName(), args.getTargetFilename(), processedName);
    } finally {
        if (localName != null) { // File was downloaded.
            activities.deleteLocalFile(localName);
        }
        if (processedName != null) { // File was processed.
            activities.deleteLocalFile(processedName);
        }
    }
}

Now we decide to calculate the processed file checksum and pass it to upload. The correct way to implement this change is:

public void processFile(Arguments args) {
    String localName = null;
    String processedName = null;
    try {
        localName = activities.download(args.getSourceBucketName(), args.getSourceFilename());
        processedName = activities.processFile(localName);
        int version = Workflow.getVersion("checksumAdded", Workflow.DEFAULT_VERSION, 1);
        if (version == Workflow.DEFAULT_VERSION) {
            activities.upload(args.getTargetBucketName(), args.getTargetFilename(), processedName);
        } else {
            long checksum = activities.calculateChecksum(processedName);
            activities.uploadWithChecksum(
                args.getTargetBucketName(), args.getTargetFilename(), processedName, checksum);
        }
    } finally {
        if (localName != null) { // File was downloaded.
            activities.deleteLocalFile(localName);
        }
        if (processedName != null) { // File was processed.
            activities.deleteLocalFile(processedName);
        }
    }
}

Later, when all Workflows that use the old version are completed, the old branch can be removed.

public void processFile(Arguments args) {
    String localName = null;
    String processedName = null;
    try {
        localName = activities.download(args.getSourceBucketName(), args.getSourceFilename());
        processedName = activities.processFile(localName);
        // getVersion call is left here to ensure that any attempt to replay history
        // for a different version fails. It can be removed later when there is no possibility
        // of this happening.
        Workflow.getVersion("checksumAdded", 1, 1);
        long checksum = activities.calculateChecksum(processedName);
        activities.uploadWithChecksum(
            args.getTargetBucketName(), args.getTargetFilename(), processedName, checksum);
    } finally {
        if (localName != null) { // File was downloaded.
            activities.deleteLocalFile(localName);
        }
        if (processedName != null) { // File was processed.
            activities.deleteLocalFile(processedName);
        }
    }
}

The Id that is passed to the getVersion call identifies the change. Each change is expected to have its own Id. But if a change spawns multiple places in the Workflow code and the new code should be either executed in all of them or in none of them, then they have to share the Id.

How to use Worker Versioning in Java

caution

Worker Versioning is currently in Pre-release, and backwards-incompatible changes are coming to the Worker Versioning APIs. For now, you need to provide dynamic configuration parameters to your Temporal Service to enable Worker Versioning:

temporal server start-dev \
   --dynamic-config-value frontend.workerVersioningDataAPIs=true \
   --dynamic-config-value frontend.workerVersioningWorkflowAPIs=true \
   --dynamic-config-value worker.buildIdScavengerEnabled=true

To use Worker Versioning in Java, you need to do the following:

Determine and assign a Build ID to your built Worker code, and opt in to versioning.
Tell the Task Queue your Worker is listening on about that Build ID, and whether its compatible with an existing Build ID.

Assign a Build ID to your Worker

Let's say you've chosen deadbeef as your Build ID, which might be a short git commit hash (a reasonable choice as Build ID). To assign it in your Worker code, assign the following Worker Options:

// ...
WorkerOptions workerOptions = WorkerOptions.newBuilder()
    .setBuildId("deadbeef")
    .setUseBuildIdForVersioning(true)
    // ...
    .build();
Worker w = workerFactory.newWorker("your_task_queue_name", workerOptions);
// ...

That's all you need to do in your Worker code. Importantly, if you start this Worker, it won't receive any tasks. That's because you need to tell the Task Queue about your Worker's Build ID first.

Tell the Task Queue about your Worker's Build ID

Now you can use the SDK (or the Temporal CLI) to tell the Task Queue about your Worker's Build ID. You might want to do this as part of your CI deployment process.

// ...
workflowClient.updateWorkerBuildIdCompatability(
    "your_task_queue_name", BuildIdOperation.newIdInNewDefaultSet("deadbeef"));

This code adds the deadbeef Build ID to the Task Queue as the sole version in a new version set, which becomes the default for the queue. New Workflows execute on Workers with this Build ID, and existing ones will continue to process by appropriately compatible Workers.

If, instead, you want to add the Build ID to an existing compatible set, you can do this:

// ...
workflowClient.updateWorkerBuildIdCompatability(
    "your_task_queue_name", BuildIdOperation.newCompatibleVersion("deadbeef", "some-existing-build-id"));

This code adds deadbeef to the existing compatible set containing some-existing-build-id and marks it as the new default Build ID for that set.

You can also promote an existing Build ID in a set to be the default for that set:

// ...
workflowClient.updateWorkerBuildIdCompatability(
    "your_task_queue_name", BuildIdOperation.promoteBuildIdWithinSet("deadbeef"));

You can also promote an entire set to become the default set for the queue. New Workflows will start using that set's default.

// ...
workflowClient.updateWorkerBuildIdCompatability(
    "your_task_queue_name", BuildIdOperation.promoteSetByBuildId("deadbeef"));

Specify versions for Commands

By default, Activities, Child Workflows, and Continue-as-New use the same compatible version set as the Workflow that invoked them if they're also using the same Task Queue.

If you want to override this behavior, you can specify your intent via the setVersioningIntent method on the ActivityOptions, ChildWorkflowOptions, or ContinueAsNewOptions objects.

For example, if you want to use the latest default version for an Activity, you can define your Activity Options like this:

// ...
private final MyActivity activity =
    Workflow.newActivityStub(
        MyActivity.class,
        ActivityOptions.newBuilder()
          .setScheduleToCloseTimeout(Duration.ofSeconds(10))
          .setVersioningIntent(VersioningIntent.VERSIONING_INTENT_DEFAULT)
          // ...other options
          .build()
    );
// ...

How to patch Workflows in Java​

How to use Worker Versioning in Java​

Assign a Build ID to your Worker​

Tell the Task Queue about your Worker's Build ID​

Specify versions for Commands​

How to patch Workflows in Java

How to use Worker Versioning in Java

Assign a Build ID to your Worker

Tell the Task Queue about your Worker's Build ID

Specify versions for Commands