Workflow Composability

[reasv]

Perhaps I just missed it, but it doesn't seem like the docs explain what happens if you call a workflow function from within a workflow.
Assuming it's the same as with Steps, I would think that this is a no-op.

I'm asking because I'd like to compose multiple workflows into one hierarchically - with the individual workflows getting the same reliability benefits as steps within workflows.

Why? Well there are actions that don't work within steps, such as waiting for a webhook.
Suppose your workflow involves scheduling a job on an external platform that updates you with webhooks.
You need to use createWebhook() at the workflow level to get the updates, and deal with all the statuses, and the results. API calls to get the result, and to schedule the job can all be individual Steps.

But what if you want to wrap the entire process of interacting with that platform and running the remote job into a Step? So this entire sub-job becomes equally retriable.
A generative AI pipeline that uses multiple providers for different stages comes to mind.

[pranaygp]

We're planning to support child workflows. Essentially, you'd be able to call a workflow within another workflow, and have retrying semantics, etc. exactly as you mentioned. So you steps are always leaf nodes in your orchestrations (since steps leave the "deterministic/replayable" workflow nature), but you can compose workflows within workflows.

Currently, yeah, it's kinda a "no op" so your child workflow just runs in the parent workflow

We're already writing workflow code at Vercel right now in a way that assumes child workflows exist, so that once we ship that, it all "just works"

[pranaygp]

Btw we would love any help here if anyone's open interested in taking a stab at implementing child workflows?