URL crawler to warm-up Swoole web-server

performance, url, crawler, prime, swoole, warm, prewarm, pre-warm, warm-up, warm up, cold


Swoole Server Warm-Up

This library pre-warms Swoole web-server by visiting given URLs on startup.

It takes time for a web-server to reach its cruising level of performance after the startup. Server warm-up is recommended to avoid first clients experiencing slowness while simultaneously overloading a cold server. This library makes it trivial to automate crawling of provided URLs to prime the server before use.


  • Visit URLs on server startup
  • Warm-up all workers at once
  • Restart workers in warm state


The library is to be installed via Composer as a dependency:

composer require upscale/swoole-warmup


Prime the server by visiting URLs on startup:

use Upscale\Swoole\Warmup;

require 'vendor/autoload.php';

$server = new \Swoole\Http\Server('', 8080);
    'dispatch_mode' => 1,

$workerState = 'cold';
$server->on('request', function ($request, $response) use (&$workerState) {
    $workerPid = getmypid();
    $response->header('Content-Type', 'text/plain');
    $response->end("Served by $workerState worker process $workerPid\n");
    $workerState = 'warm';

$crawler = new Warmup\Crawler($server, new Warmup\RequestFactory($server));



The warm-up mechanism is much more advanced than an ordinary HTTP crawler. First off, it dispatches requests before the server accepts any incoming connections. Secondly, the dispatch is carried out internally avoiding the overhead of external HTTP requests. Finally, the warm-up is performed in the main process used as an exemplar for forking worker processes. The warm-up extends to all workers altogether and the optimization effects persist beyond the lifetime of worker processes. Swoole workers are subject to periodic restart according to the max_request setting as a memory leak mitigation measure.


Pull Requests with fixes and improvements are welcome!


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Licensed under the Apache License, Version 2.0.