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Signal-Driven Workflow

Pause a workflow and wait for an external signal before continuing.

What you will learn​

  • How to pause a workflow and wait for a Temporal signal using listen
  • How to access signal payload in subsequent tasks
  • How to configure a wait timeout to avoid indefinite blocking

Workflow​

workflow.yaml
document:
  dsl: 1.0.0
  namespace: zigflow
  name: signal
  version: 0.0.1
do:
  - approveListener:
      metadata:
        timeout: 10s
      listen:
        to:
          one:
            with:
              id: approve
              type: signal
  - outputSignal:
      export:
        as: '${ $context + { response: . } }'
      set:
        signal: ${ $data.approveListener }
  - wait:
      output:
        as: ${ $context }
      wait:
        seconds: 5

Explanation​

PartPurpose
listen.to.oneWait for exactly one matching event
id: approveThe Temporal signal name to listen for
type: signalWrite-only, fire-and-forget from the sender
metadata.timeoutHow long to wait before timing out (default 60s)
$data.approveListenerSignal payload, accessed by task name

How to run​

  1. Start a Temporal development server:

    temporal server start-dev

  2. Start the worker:

    zigflow run -f workflow.yaml

  3. Start a workflow execution:

    temporal workflow start \
      --type signal \
      --task-queue zigflow \
      --workflow-id approval-1

  4. Send the signal from a separate terminal:

    temporal workflow signal \
      --workflow-id approval-1 \
      --name approve \
      --input '{"approved": true}'

  5. View the result:

    temporal workflow show --workflow-id approval-1

Expected behaviour​

After you send the signal, the workflow reads the payload from $data.approveListener, stores it under signal and then waits 5 seconds before completing.

If no signal arrives within the timeout period, the listen task times out.

Common mistakes​

Signal data is not in $output. After a signal is received its payload is accessible via $data.<taskName>, not $output.

The workflow times out before the signal arrives. The default timeout is 60 seconds. Increase metadata.timeout for workflows that need to wait longer.