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Set

A task used to set data to the workflow's state.

When to use this​

Use Set whenever you need to write data into the workflow state. Always use Set for generated values (UUIDs, timestamps) to ensure determinism during Temporal replay.

warning

A Temporal workflow MUST be deterministic.

You are strongly advised to use the Set task when setting data, especially generated data (such as ${ uuid }), rather than invoking it in a task. For example, the following CallHTTP task would return a Non-Determinism Error (NDE) if it was replayed:

# Bad ❌
- updateUser:
    call: http
    output:
      as: '${ { response: . } }'
    with:
      method: put
      headers:
        content-type: application/json
      endpoint: https://echo.free.beeceptor.com
      body:
        id: ${ uuid } # This value is different every time this task is run
        hello: world

However, as this one generates the UUID in a Set task, this is wrapped in such a way that it's saved to the Temporal state and is safe to replay.

- set:
    export:
      as:
        data: ${ . }
    set:
      id: ${ uuid }
- updateUser:
    call: http
    output:
      as: '${ $context + { response: . } }'
    with:
      method: put
      headers:
        content-type: application/json
      endpoint: https://echo.free.beeceptor.com
      body:
        id: ${ $data.id }
        hello: world

With great power comes great responsibility

Properties​

NameTypeRequiredDescription
setmapyesThe data to set.

Example​

The data is saved to a state object and can be retrieved in a later task by calling ${ $data.<key> }. Once set, it remains in the state and can be overidden by a later Set task.

document:
  dsl: 1.0.0
  namespace: zigflow
  name: example
  version: 0.0.1
do:
  - baseData:
      # Set the output to the context
      export:
        as: ${ . }
      set:
        # This value will be overidden later
        progress: 0
        # Set a variable from an envvar
        envvar: ${ $env.EXAMPLE_ENVVAR }
        # Generate a UUID
        uuid: ${ uuid }
        # Insert something from the input
        inputUserId: ${ $input.userId }
        # Maps can be used
        object:
          hello: world
          uuid: ${ uuid }
        # As can arrays
        array:
          - ${ uuid }
          - hello: world
  - updateProgress:
      # Merge this set with the context and output everything together
      output:
        as: ${ $context + . }
      set:
        # Overidden from above. Everything else remains the same
        progress: 100

Gotchas​

Generated values (UUID, timestamps) used outside a set task cause Non-Determinism Errors on replay. See the warning at the top of this page.

set data persists for the lifetime of the workflow. A later set task with the same key overwrites the value; all other keys remain.