Polling

When working with asynchronous operations, many APIs return immediately with a job ID or task reference, requiring you to poll for completion status. The loopUntil option in lam.httpRequest and lam.httpRequests allows you to automatically poll an endpoint until a specific condition is met.

The polling functionality is optional; just add a loopUntil object with a condition function to your HTTP request.

Important: Polling is not enabled by default. You must explicitly specify polling behavior when creating your workflow steps.

loopUntil Properties

Property	Type	Required	Default	Description
condition	String (JavaScript function)	Yes	-	Function that receives ctx object and returns boolean. When true, polling stops.
maxAttempts	Number	No	10	Maximum number of polling attempts before giving up
strategy	String	No	'fixed'	Delay strategy: 'fixed' or 'exponential'
initialDelay	String	No	'1s'	Initial delay between polls (e.g., '1s', '500ms', '2m')
maxDelay	String	No	'30s'	Maximum delay between polls for exponential strategy
multiplier	Number	No	2	Multiplier for exponential backoff strategy

The condition function receives a ctx object with:

• ctx.response - The parsed response body

• ctx.status - HTTP status code

• ctx.headers - Response headers

Example: Suppose we're starting a data processing job that takes time to complete, and we need to wait for it to finish before proceeding.

Start Data Processing Job

(data) => {
  const { input } = data;

  return {
    "lam.httpRequest": {
      method: "POST",
      url: "{{config.dataProcessorUrl}}/api/jobs",
      headers: {
        Authorization: "Bearer {{config.processorApiKey}}",
        "Content-Type": "application/json",
      },
      body: {
        datasetId: input.datasetId,
        operation: "transform",
        outputFormat: "parquet",
      },
      // Poll until job completes
      loopUntil: {
        condition: "(ctx) => ctx.response.status === 'completed'",
        maxAttempts: 20,
        strategy: "exponential",
        initialDelay: "2s",
        maxDelay: "60s",
      },
    },
  };
};