trigger one workflow from another workflow

[dhiaayachi]

I was wondering if it was possible to trigger one workflow using another workflow? For instance: can workflow A trigger workflow B and can workflow B access outputs from workflow A's activity?

We want to build two different workflows for two different teams that share the same temporal server

[dhiaayachi]

Thank you for your question!

Temporal does not currently support triggering one workflow from another directly. However, you can achieve similar functionality using Signals.

Workflow A can send a Signal to Workflow B with the information Workflow B needs to start its execution. Workflow B can then use this information to process its tasks.

Here's a simple example of how this might work:

Workflow A:

signalWorkflowB(input):
  emit signal "startWorkflowB" with payload input

Workflow B:

onSignal "startWorkflowB"(input):
  process tasks based on input

For more information on Signals, please refer to the Workflow Message Passing page.

[dhiaayachi]

Thanks for reaching out! It is definitely possible to trigger one workflow using another workflow. You can use child workflows to achieve this.

Here's how it works:

• Workflow A can start Workflow B using the startChild function. This function will create a new instance of Workflow B and execute it as a child of Workflow A.
• Workflow B can access outputs from Workflow A using the WorkflowInfo function. This function will give you access to information about the currently executing workflow, including its workflow ID, run ID, and any data that was passed to it as input.

Let me know if you have any more questions!

[dhiaayachi]

Thanks for reaching out! You are right, it is possible to trigger one workflow from another. The Child Workflow Execution is a workflow execution spawned from another workflow. Workflow A can trigger Workflow B using the Child Workflow API. You can also access outputs from Workflow A's activity from Workflow B.

Workflow A would be the parent workflow, and Workflow B would be the child workflow. The parent workflow can monitor the child workflow's lifecycle and can wait for its completion or results. For example, you can wait for Workflow B to complete before proceeding with Workflow A or access the outputs from Workflow B.

There are two ways to start a Child Workflow Execution and return a handle to it, use startChild. For an example, check the code in child-workflows/src/workflows.ts.

You can learn more about child workflows and the Parent Close Policy to understand how a child workflow execution is terminated. You can find the implementation details for each SDK in the respective documentation.