Patching API

This sample shows how to use the patching/versioning API to update the code of a Workflow that has executions in progress in production.

Running this sample

1. temporal server start-dev to start Temporal Server.
2. npm install to install dependencies.
3. npm run start.watch to start the Worker.
4. In another shell, npm run workflow to run the v1 Workflow.
5. Now we need to simulate a migration: patch in the new code

• Go into src/workflows.ts and swap workflows-v1 for workflows-v2.
• Wait for the Worker to rebuild (back in the npm run start.watch shell).
• Start a v2 Workflow with npm run workflow. This will run alongside the v1 Workflow.
• You can see the deprecation marker recorded in Temporal Web for the v2 Workflow.

6. Step 2 of the migration: deprecate the patch

• Manually terminate the v1 Workflow. We only deprecate the patch when all instances of v1 are no longer running.
• Go into src/workflows.ts and swap workflows-v2 for workflows-v3.
• Wait for the Worker to rebuild.
• Start a v3 Workflow with npm run workflow. This will run alongside the v2 Workflow.

7. Step 3 of the migration: Solely deploy new code

• Manually terminate the v2 Workflow. We only remove the deprecation when all instances of v2 are no longer running.
• Go into src/workflows.ts and swap workflows-v3 for workflows-vFinal.
• etc.