loop

Create runtime iterations from a count, rows, directory files, trigger events, or an infinite source.

When to use it

Use a loop when the work items are known only at runtime. The loop routes each iteration into its body; it is not a scheduler or an agent-specific mode.

Example

Rattish: 1

Workflow:
  name: Iterate work

Node step:
  type: loop
  source:
    type: count
    count: 3
    max-concurrency: 1
    fail-fast: true
  to: record

Node record:
  type: bash-command
  command: echo iteration-complete
  needs: step

source.type accepts count, tabular, directory, trigger-events, and infinite. Count defaults to one and allows zero. Tabular and directory sources require a path. Directory defaults to glob * and no content; trigger events can also opt into content.

Every source defaults to one overlapping iteration and fail-fast: false. source.max-concurrency limits iterations, while the common node max-concurrency limits activations of an individual node. Both limits apply, and a body node's own limit also defaults to one. To run three iterations at once, set max-concurrency: 3 on the loop source and on each body node; the compiler warns when a body node would hold a parallel loop back. Use limits appropriate for shared file writes.

Node items:
  type: loop
  source: {"type": "count", "count": 6, "max-concurrency": 3}
  to: work

Node work:
  type: bash-command
  command: sleep 1
  needs: items
  max-concurrency: 3

Bind from node.step.output inside the body, not from a loop.* alias. Iteration fields depend on the source: count items carry index; directory items include path, name, and directory, with file_content when requested. Refer to the compiled contract before assuming fields for other source types.

Directory and tabular files are opened at activation, after upstream nodes. Zero matching files succeeds with zero body activations. Infinite work needs a break, timeout, or run limit.

Configuration

Configuration fields use hyphens. These are the node-specific fields; shared execution fields apply separately.

Field	Type	Required / default	Meaning
source	object	Required	Iteration source; its nested fields depend on type.

Inputs and output

This node has no declared input ports. Configure its authored fields directly.

The source contract returns an object; the runtime exposes iteration-specific data to body activations. Do not treat every source type as if it has the same fields.

Preflight and limits

Filesystem-backed sources require a path, but availability is checked when the loop activates. Source sizes and aggregate reads have runtime bounds. Read Loops and fan-out for lifecycle and concurrency details.

Use Raticode rattish check and Raticode rattish preflight before choosing to run the example. The installed contract is available through Raticode rattish docs --format json.

Continue with Node reference, Routes and joins, or Runs and approvals.