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Aftabul Islam
Aftabul Islam

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Laravel Waiting Request

#laravel #backend #php #architecture

The Problem

You are processing some data through background job. But before the processing is done, another request had been made to read the related data.

In this case you are either providing a historic data or serving wrong information.

Solution

Holding the request until the job is executed, could be the simplest solution.
I am not saying it is the only solution, but the simplest one.

Some Scenarios

Lets discuss about some possible scenarios.

Booking Job

When a user request to book a resource between two specifics dates. Let's assume that it is done by a job. So it might take some time in production load.
In the meantime if another request is asking for that specific users booking data.

File Importing Job

User uploads a file like CSV or XML, you have accepted the file but it also needs processing, which should be done in by a job.
If the user ask for the status of the CSV resource in another request.

The Package

aihimel/laravel-waiting-request is a small Laravel package that solves exactly this — it lets one request park until another piece of work (a job, a sync, a long-running controller action) signals that the resource is ready to read.

Install 

composer require aihimel/laravel-waiting-request
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Optionally publish the config:

php artisan vendor:publish --tag="waiting-request-config"
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How it works

The package exposes a tiny API around four ideas: block, wait, check, resolve. Under the hood it is backed by your Laravel cache — no extra infrastructure, no queue plumbing.

A blocker is identified by a class path and a resource id. That pair becomes a unique cache key, so blockers are per-resource (booking 42 does not interfere with booking 43).

use Aihimel\LaravelWaitingRequest\Facades\LWRequest;

// 1. Block — call this where the background work *starts*
LWRequest::addBlocker(Booking::class, $booking->id);

// 2. Wait — call this in the request that wants to read the resource
$resolved = LWRequest::whenResolved(Booking::class, $booking->id);

if ($resolved) {
    return BookingResource::make($booking->fresh());
}

return response()->json(['message' => 'Still processing, try again'], 202);

// 3. Resolve — call this when the background work finishes
LWRequest::resolveBlocker(Booking::class, $booking->id);
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You can also peek without waiting:

if (LWRequest::isBlocked(Booking::class, $booking->id)) {
    // resource is mid-flight
}
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Applying it to the scenarios

Booking job. The controller that accepts the booking calls addBlocker(Booking::class, $id) and dispatches the job. The job calls resolveBlocker(...) in its handle() (or in a finally block). Any reader that hits GET /bookings/{id} in the meantime calls whenResolved(...) first and only reads the model once the writer is done.

File importing job. Same shape: addBlocker(Import::class, $import->id) when the upload is accepted, resolveBlocker(...) when the parser finishes (success or failure — both should release). The status endpoint calls whenResolved(...) so the client gets a settled answer instead of a half-imported snapshot.

Sensible defaults you can tune

Every knob lives in config/waiting-request.php and is overridable via env:

Config Env Default What it does
cache_prefix LW_REQUEST_CACHE_PREFIX lw_request_ Namespace for cache keys
timeout LW_REQUEST_MAX_WAITING_TIME 5 How long whenResolved() waits before giving up (seconds)
check_interval LW_REQUEST_CHECK_INTERVAL 250 Poll interval inside whenResolved() (milliseconds)
max_blocking_time LW_REQUEST_MAX_BLOCKING_TIME 10 Max lifetime of a blocker before it auto-expires (seconds)

addBlocker() takes an optional third argument so you can bump the TTL per call when you know a particular job runs longer:

LWRequest::addBlocker(Import::class, $import->id, 120); // 2 minutes
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Why the blocker has a lifetime

If a job crashes before calling resolveBlocker(), you do not want readers to wait forever. From v2.x every blocker carries a Unix expiry timestamp. The next isBlocked() / whenResolved() call after that timestamp will:

  1. Forget the cache entry, and
  2. Emit Log::warning('Waiting-request blocker expired without being resolved', [...])

So even if your job dies, traffic recovers on its own and you get a log line telling you it happened.

Do's and Don'ts

Do

  • Do release the blocker in finally. Wrap your job body so a thrown exception still hits resolveBlocker(). Auto-expiry is a backstop, not a happy path.
  • Do set max_blocking_time to comfortably exceed your worst-case job duration. If your import averages 8s and worst-cases at 25s, a 10s default will auto-release while the job is still running — defeating the lock.
  • Do tune timeout to match your UX budget. If a client is willing to wait 2s for a synchronous response, set timeout=2; do not let whenResolved() hold an HTTP worker for 30s.
  • Do flush the cache when upgrading from 1.x to 2.x. Pre-upgrade values stored as true will be read as 1, treated as already-expired, and produce a one-time burst of warning logs.
  • Do treat a false return from whenResolved() as "still pending". Respond with 202 Accepted (or similar) and let the client poll — do not pretend the data is ready.

Don't

  • Don't put isBlocked() on a hot, read-only path you expect to be side-effect-free. It evicts expired entries and writes a log line. That is intentional, but worth knowing.
  • Don't use it as a distributed mutex for writes. This package is for readers waiting on writers on a best-effort basis. If two writers race, Cache::add() will reject the second addBlocker() (it returns false), but the package does not give you queueing, fairness, or strict mutual exclusion.
  • Don't share a single blocker across unrelated resources. Key it by the real resource (Booking::class + $id), not by something coarse like the user id, or you will block requests that have nothing to do with each other.
  • Don't forget the cache driver matters. array or file drivers will not work across processes. In production, use redis / memcached so the worker that resolves the blocker and the web process that is waiting actually share the same cache.
  • Don't lean on whenResolved() from a queue worker. Polling inside a worker burns a worker slot. Workers should resolve blockers, not wait on them.

That's the whole package — a couple of facade calls, a cache key per resource, and a sane expiry so nothing wedges. If you've ever shipped a ?retry=true hack or a sleep-and-pray in a controller, this is the cleaner version of that.

Source & issues: github.com/aihimel/laravel-waiting-request

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