Daemon Bundle Laravel Package

Getting Started

Minimal Setup

1. Install Dependencies Ensure pcntl is enabled in your PHP binary. For Ubuntu/Debian:

   sudo apt-get install php-pcntl
   

   Restart your web server and PHP-FPM if applicable.

2. Add Bundle to composer.json

   {
       "require": {
           "code-meme/daemon-bundle": "dev-master"
       }
   }
   

   Run composer update.

3. Register Bundle Add to config/bundles.php:

   return [
       // ...
       CodeMeme\DaemonBundle\CodeMemeDaemonBundle::class => ['all' => true],
   ];
   

4. First Daemon Command Create a console command extending DaemonCommand:

   // src/Command/MyDaemonCommand.php
   namespace App\Command;
   
   use CodeMeme\DaemonBundle\Command\DaemonCommand;
   use Symfony\Component\Console\Input\InputInterface;
   use Symfony\Component\Console\Output\OutputInterface;
   
   class MyDaemonCommand extends DaemonCommand
   {
       protected function execute(InputInterface $input, OutputInterface $output)
       {
           while (true) {
               $output->writeln('Running daemon task...');
               sleep(10);
           }
       }
   }
   

5. Run the Daemon

   php bin/console my:daemon
   

Implementation Patterns

Workflows

1. Daemonizing Existing Commands Convert any Command into a daemon by extending DaemonCommand and overriding execute(). Example:

   class BackgroundProcessorCommand extends DaemonCommand
   {
       protected function execute(InputInterface $input, OutputInterface $output)
       {
           while (!$this->isTerminated()) {
               $this->processQueue();
               sleep(5);
           }
       }
   }
   

2. Signal Handling Leverage built-in signal handling (e.g., SIGTERM, SIGINT) via isTerminated():

   while (!$this->isTerminated()) {
       // Long-running task
   }
   

3. Logging Use Symfony’s logger in execute():

   $this->getLogger()->info('Daemon started');
   

4. Configuration Inject services via constructor or getContainer():

   public function __construct(private MyService $service) {}
   

5. Supervisor Integration Configure Supervisor to manage daemons (e.g., auto-restart on crash):

   [program:my_daemon]
   command=php /path/to/bin/console my:daemon
   autostart=true
   autorestart=true
   user=www-data
   

Gotchas and Tips

Pitfalls

1. pcntl Requirement

   • Error: FatalErrorException: Class 'pcntl_signal' not found.
   • Fix: Ensure php-pcntl is installed and enabled in php.ini (extension=pcntl).

2. Permissions

   • Daemons run with limited privileges. Use setuid() or configure Supervisor to run as a specific user.
   • Tip: Test with sudo -u www-data php bin/console my:daemon to debug permission issues.

3. Zombie Processes

   • If the daemon crashes, orphaned processes may linger.
   • Fix: Use Supervisor or implement cleanup in terminate():

     protected function terminate(InputInterface $input, OutputInterface $output)
     {
         posix_kill(posix_getpid(), SIGTERM);
     }
     

4. Logging to File

   • Console output may not persist. Redirect logs to a file:

     $output = new StreamOutput(fopen('daemon.log', 'a'));
     $this->execute($input, $output);
     

5. Debugging

   • Tip: Add a debug flag to dump state:

     if ($input->getOption('debug')) {
         var_dump($this->getContainer()->getParameter('some_param'));
     }
     

Tips

1. Graceful Shutdown Override terminate() to handle cleanup:

   protected function terminate(InputInterface $input, OutputInterface $output)
   {
       $this->getLogger()->info('Shutting down gracefully...');
       // Close DB connections, release locks, etc.
   }
   

2. Environment Awareness Use APP_ENV to disable daemons in dev:

   if ('dev' === $this->getContainer()->getParameter('kernel.environment')) {
       throw new \RuntimeException('Daemons disabled in dev environment.');
   }
   

3. Resource Limits Daemons may hit memory limits. Use set_time_limit() or ini_set('memory_limit', '-1') cautiously.

4. Testing Mock DaemonCommand in tests by extending it and overriding isTerminated():

   $command = $this->getMockBuilder(MyDaemonCommand::class)
       ->onlyMethods(['isTerminated'])
       ->getMock();
   $command->method('isTerminated')->willReturn(true);
   

5. Extending Functionality

   • Custom Signals: Extend System_Daemon behavior by overriding DaemonCommand::setupSignals().
   • PID File: Use $this->getPidFile() to manage PID files:

     $pidFile = $this->getPidFile();
     if (file_exists($pidFile)) {
         $output->writeln('Daemon already running!');
         return 1;
     }