Postman - how to loop request until I get a specific response?

Question

I'm testing API with Postman and I have a problem: My request goes to sort of middleware, so either I receive a full 1000+ line JSON, or I receive PENDING status and empty array of results:

The question is, how to loop this request in Postman until I will get status SUCCESS and results array > 0? When I'm sending those requests manually one-by-one it's ok, but when I'm running them through Collection Runner, "PENDING" messes up everything.

Answer 1

I found an awesome post about retrying a failed request by Christian Baumann which allowed me to find a suitable approach to the exact same problem of first polling the status of some operation and only when it's complete run the actual tests.

The code I'd end up if I were you is:

const maxNumberOfTries = 3; // your max number of tries
const sleepBetweenTries = 5000; // your interval between attempts

if (!pm.environment.get("tries")) {
    pm.environment.set("tries", 1);
}

const jsonData = pm.response.json();

if ((jsonData.meta.status !== "SUCCESS" && jsonData.results.length === 0) && (pm.environment.get("tries") < maxNumberOfTries)) {
     const tries = parseInt(pm.environment.get("tries"), 10);
     pm.environment.set("tries", tries + 1);
     setTimeout(function() {}, sleepBetweenTries);
     postman.setNextRequest(request.name);
 } else {
     pm.environment.unset("tries");

     // your actual tests go here...
}

What I liked about this approach is that the call postman.setNextRequest(request.name) doesn't have any hardcoded request names. The downside I see with this approach is that if you run such request as a part of the collection, it will be repeated a number of times, which might bloat your logs with unnecessary noise.

The alternative I was considering is writhing a Pre-request Script which will do polling (by sending a request) and spinning until the status is some kind of completion. The downside of this approach is the need for much more code for the same logic.