Versioning - Go SDK

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

Temporal Go SDK Patching APIs

The definition code of a Temporal Workflow must be deterministic because Temporal uses event sourcing to reconstruct the Workflow state by replaying the saved history event data on the Workflow definition code. This means that any incompatible update to the Workflow Definition code could cause a non-deterministic issue if not handled correctly.

Because we design for potentially long running Workflows at scale, versioning with Temporal works differently. We explain more in this optional 30 minute introduction: https://www.youtube.com/watch?v=kkP899WxgzY

Consider the following Workflow Definition:

func YourWorkflow(ctx workflow.Context, data string) (string, error) {
        ao := workflow.ActivityOptions{
                ScheduleToStartTimeout: time.Minute,
                StartToCloseTimeout:    time.Minute,
        }
        ctx = workflow.WithActivityOptions(ctx, ao)
        var result1 string
        err := workflow.ExecuteActivity(ctx, ActivityA, data).Get(ctx, &result1)
        if err != nil {
                return "", err
        }
        var result2 string
        err = workflow.ExecuteActivity(ctx, ActivityB, result1).Get(ctx, &result2)
        return result2, err
}

Now let's say we replaced ActivityA with ActivityC and deployed the updated code. If an existing Workflow Execution was started by the original version of the Workflow code, where ActivityA had already completed and the result was recorded to history, the new version of the Workflow code picks up that Workflow Execution and tries to resume from there. However, the Workflow will fail because the new code expects a result for ActivityC from the history data, but instead it gets the result for ActivityA. This causes the Workflow to fail on the non-deterministic error.

Thus we use workflow.GetVersion().

var err error
v := workflow.GetVersion(ctx, "Step1", workflow.DefaultVersion, 1)
if v == workflow.DefaultVersion {
        err = workflow.ExecuteActivity(ctx, ActivityA, data).Get(ctx, &result1)
} else {
        err = workflow.ExecuteActivity(ctx, ActivityC, data).Get(ctx, &result1)
}
if err != nil {
        return "", err
}

var result2 string
err = workflow.ExecuteActivity(ctx, ActivityB, result1).Get(ctx, &result2)
return result2, err

When workflow.GetVersion() is run for the new Workflow Execution, it records a marker in the Workflow history so that all future calls to GetVersion for this change Id—Step 1 in the example—on this Workflow Execution will always return the given version number, which is 1 in the example.

If you make an additional change, such as replacing ActivityC with ActivityD, you need to add some additional code:

v := workflow.GetVersion(ctx, "Step1", workflow.DefaultVersion, 2)
if v == workflow.DefaultVersion {
        err = workflow.ExecuteActivity(ctx, ActivityA, data).Get(ctx, &result1)
} else if v == 1 {
        err = workflow.ExecuteActivity(ctx, ActivityC, data).Get(ctx, &result1)
} else {
        err = workflow.ExecuteActivity(ctx, ActivityD, data).Get(ctx, &result1)
}

Note that we changed maxSupported from 1 to 2. A Workflow that has already passed this GetVersion() call before it was introduced returns DefaultVersion. A Workflow that was run with maxSupported set to 1 returns 1. New Workflows return 2.

After you are sure that all of the Workflow Executions prior to version 1 have completed, you can remove the code for that version. It should now look like the following:

v := workflow.GetVersion(ctx, "Step1", 1, 2)
if v == 1 {
        err = workflow.ExecuteActivity(ctx, ActivityC, data).Get(ctx, &result1)
} else {
        err = workflow.ExecuteActivity(ctx, ActivityD, data).Get(ctx, &result1)
}

You'll note that minSupported has changed from DefaultVersion to 1. If an older version of the Workflow Execution history is replayed on this code, it fails because the minimum expected version is 1. After you are sure that all of the Workflow Executions for version 1 have completed, you can remove version 1 so that your code looks like the following:

_ := workflow.GetVersion(ctx, "Step1", 2, 2)
err = workflow.ExecuteActivity(ctx, ActivityD, data).Get(ctx, &result1)

Note that we have preserved the call to GetVersion(). There are two reasons to preserve this call:

This ensures that if there is a Workflow Execution still running for an older version, it will fail here and not proceed.
If you need to make additional changes for Step1, such as changing ActivityD to ActivityE, you only need to update maxVersion from 2 to 3 and branch from there.

You need to preserve only the first call to GetVersion() for each changeID. All subsequent calls to GetVersion() with the same change Id are safe to remove. If necessary, you can remove the first GetVersion() call, but you need to ensure the following:

All executions with an older version are completed.
You can no longer use Step1 for the changeId. If you need to make changes to that same part in the future, such as change from ActivityD to ActivityE, you would need to use a different changeId like Step1-fix2, and start minVersion from DefaultVersion again. The code would look like the following:

v := workflow.GetVersion(ctx, "Step1-fix2", workflow.DefaultVersion, 1)
if v == workflow.DefaultVersion {
        err = workflow.ExecuteActivity(ctx, ActivityD, data).Get(ctx, &result1)
} else {
        err = workflow.ExecuteActivity(ctx, ActivityE, data).Get(ctx, &result1)
}

Upgrading a Workflow is straightforward if you don't need to preserve your currently running Workflow Executions. You can simply terminate all of the currently running Workflow Executions and suspend new ones from being created while you deploy the new version of your Workflow code, which does not use GetVersion(), and then resume Workflow creation. However, that is often not the case, and you need to take care of the currently running Workflow Executions, so using GetVersion() to update your code is the method to use.

However, if you want your currently running Workflows to proceed based on the current Workflow logic, but you want to ensure new Workflows are running on new logic, you can define your Workflow as a new WorkflowType, and change your start path (calls to StartWorkflow()) to start the new Workflow type.

Sanity checking

The Temporal client SDK performs a sanity check to help prevent obvious incompatible changes. The sanity check verifies whether a Command made in replay matches the event recorded in history, in the same order. The Command is generated by calling any of the following methods:

workflow.ExecuteActivity()
workflow.ExecuteChildWorkflow()
workflow.NewTimer()
workflow.RequestCancelWorkflow()
workflow.SideEffect()
workflow.SignalExternalWorkflow()
workflow.Sleep()

Adding, removing, or reordering any of the preceding methods triggers the sanity check and results in a non-deterministic error.

The sanity check does not perform a thorough check. For example, it does not check on the Activity's input arguments or the Timer duration. If the check is enforced on every property, it becomes too restrictive and harder to maintain the Workflow code. For example, if you move your Activity code from one package to another package, that move changes the ActivityType, which technically becomes a different Activity. But we don't want to fail on that change, so we check only the function name part of the ActivityType.

How to use Worker Versioning in Go

caution

Worker Versioning is currently in Pre-release.

See the Pre-release README for more information.

A Build ID corresponds to a deployment. If you don't already have one, we recommend a hash of the code--such as a Git SHA--combined with a human-readable timestamp. To use Worker Versioning, you need to pass a Build ID to your Go Worker and opt in to Worker Versioning.

Assign a Build ID to your Worker and opt in to Worker Versioning

You should understand assignment rules before completing this step. See the Worker Versioning Pre-release README for more information.

To enable Worker Versioning for your Worker, assign the Build ID--perhaps from an environment variable--and turn it on.

// ...
workerOptions := worker.Options{
   BuildID: buildID,
   UseBuildIDForVersioning: true,
// ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

danger

Importantly, when you start this Worker, it won't receive any tasks until you set up assignment rules.

Specify versions for Activities, Child Workflows, and Continue-as-New Workflows

By default, Activities, Child Workflows, and Continue-as-New Workflows are run on the build of the Workflow that created them if they are also configured to run on the same Task Queue. When configured to run on a separate Task Queue, they will default to using the current assignment rules.

If you want to override this behavior, you can specify your intent via the VersioningIntent field on the appropriate options struct.

For example, if you want an Activity to use the latest assignment rules rather than inheriting from its parent:

// ...
ao := workflow.ActivityOptions{
    VersioningIntent: VersioningIntentUseAssignmentRules,
    // ...other options
}
activityCtx := workflow.WithActivityOptions(ctx, ao)
var yourActivityResult YourActivityResultType
err := workflow.ExecuteActivity(ctx, YourActivityDefinition, yourActivityParam).Get(ctx, &yourActivityResult)
// ...

Specifying versions for Continue-As-New

When using the Continue-As-New feature, use the WithWorkflowVersioningIntent context modifier:

ctx = workflow.WithWorkflowVersioningIntent(ctx, temporal.VersioningIntentUseAssignmentRules)
err := workflow.NewContinueAsNewError(ctx, "WorkflowName")

Tell the Task Queue about your Worker's Build ID (Deprecated)

caution

This section is for a previous Worker Versioning API that is deprecated and will go away at some point. Please redirect your attention to Worker Versioning.

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.

// ...
err := client.UpdateWorkerBuildIdCompatibility(ctx, &client.UpdateWorkerBuildIdCompatibilityOptions{
   TaskQueue: "your_task_queue_name",
   Operation: &client.BuildIDOpAddNewIDInNewDefaultSet{
      BuildID: "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:

// ...
err := client.UpdateWorkerBuildIdCompatibility(ctx, &client.UpdateWorkerBuildIdCompatibilityOptions{
   TaskQueue: "your_task_queue_name",
   Operation: &client.BuildIDOpAddNewCompatibleVersion{
      BuildID:                   "deadbeef",
      ExistingCompatibleBuildId: "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:

// ...
err := client.UpdateWorkerBuildIdCompatibility(ctx, &client.UpdateWorkerBuildIdCompatibilityOptions{
   TaskQueue: "your_task_queue_name",
   Operation: &client.BuildIDPromoteIDWithinSet{
      BuildID: "some-existing-build-id",
   },
})

Temporal Go SDK Patching APIs​

Sanity checking​

How to use Worker Versioning in Go​

Assign a Build ID to your Worker and opt in to Worker Versioning​

Specify versions for Activities, Child Workflows, and Continue-as-New Workflows​

Specifying versions for Continue-As-New​

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