Flowlets & Islets

Flowlets & Islets

Flowlet Structure

A flowlet is the full configuration of one step in a flow:

{
  "name": "Send Notification",
  "ref": "sendNotification",
  "appId": "send-mail",
  "index": 2,
  "args": {
    "to": "{{ $prev.getUser.email }}",
    "subject": "Your report is ready",
    "body": "<p>Report attached.</p>",
    "attachments": ["{{ $prev.generateReport.filePath }}"]
  },
  "timeout": 15,
  "retry": {
    "count": 2,
    "delayMs": 500,
    "backoffMultiplier": 2,
    "jitter": true
  },
  "filters": [...],
  "needsApproval": false,
  "componentConfigIds": {
    "request": "65smtp-component-id"
  }
}

Filters

Filters are pre-execution conditions. The flowlet only runs if all filters evaluate to true.

"filters": [
  {
    "leftValue": "{{ $prev.checkBalance.amount }}",
    "operator": "gte",
    "rightValue": "1000",
    "cast": "number",
    "mode": "and"
  },
  {
    "leftValue": "{{ $prev.getUser.tier }}",
    "operator": "eq",
    "rightValue": "premium",
    "mode": "and"
  }
]

Filter fields:

• leftValue — expression or static value (left side of comparison)
• operator — eq, neq, gt, gte, lt, lte, contains, not_contains, is_empty, not_empty, regex
• rightValue — value to compare against
• cast — type cast before comparison: string, number, boolean
• mode — and (all must pass) or or (any must pass)

Retry Configuration

"retry": {
  "count": 3,
  "delayMs": 1000,
  "backoffMultiplier": 2.0,
  "jitter": true
}

• count: max retry attempts after the first failure
• delayMs: initial delay before first retry
• backoffMultiplier: multiply delay by this factor on each retry (exponential backoff)
• jitter: add random variation to delay to prevent thundering herd

With count: 3, delayMs: 1000, backoffMultiplier: 2:

• Attempt 1: immediate
• Retry 1: after ~1s
• Retry 2: after ~2s
• Retry 3: after ~4s

Timeout

"timeout": 30

Timeout in seconds. If the module does not complete within this time, the flowlet fails with a timeout error. The retry logic then applies.

Approval Gates

When needsApproval: true, the play pauses at that step and enters WAIT state. An approval request is sent to the designated user:

{
  "ref": "approvePayment",
  "appId": "var",
  "needsApproval": true,
  "args": {"approvalNote": "Please review the ${{ $prev.calcTotal.amount }} payment"}
}

The play only continues after the user approves via the UI or API. If declined, the play moves to FAIL.

Component Override Per Flowlet

Override the default component for a specific step:

"componentConfigIds": {
  "ai": "65anthropic-component-id",
  "storage": "65s3-prod-component-id"
}

This lets you use a specific AI provider or storage backend for just this step, without affecting other steps in the flow.

Islets

Islets are isolated sub-executions within a play. They run in their own execution context, separate from the main play’s state. Used for:

• Running a set of steps against each item in a collection (powered by the Iterator module)
• Fire-and-forget side effects that shouldn’t block the main flow
• Parallel processing branches that merge back via Aggregator