phlib/console-process

Console signal implementation using PHPs Process control functions.

There are 2 implementations.

1. Background command. Repeatedly execute a command, until interrupted using the signal handler.
2. Daemon command. Builds on the Background command to allow forking (detaching) the process.

Install

Via Composer

$ composer require phlib/console-process

Background Command

Basic Usage

The Background Command is implemented in the same way as you're used to with the normal Symfony Command, however it must allow for the execute() method to be called multiple times. There is a processing delay between each execution which can be customised.

<?php

declare(strict_types=1);

use Phlib\Console\Command\BackgroundCommand;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Output\OutputInterface;

class MyProcessCommand extends BackgroundCommand
{
    protected function configure(): void
    {
        $this->setName('my:process')
            ->setDescription('My background process.');
    }

    protected function execute(InputInterface $input, OutputInterface $output): int
    {
        $output->writeln('Doing important work!');
        return 0;
    }
}

Stopping execution

Normal usage

Typically, the command will continue execution until interrupted by a signal, e.g. a user pressing Ctrl+C.

Self-termination

Alternatively, if an implementation has a finite task, for example deleting records in batches, it may need to terminate itself once the task is complete. This is done by calling shutdown().

class MyProcessCommand extends BackgroundCommand
{
    // ...
    
    protected function execute(InputInterface $input, OutputInterface $output): int
    {
        $countDeleted = $this->deleteBatchOfRecords();
        if ($countDeleted === 0) {
            $output->writeln('All done!');
            $this->shutdown();
        }
        return 0;
    }
}

Non-zero exit

If an execution returns a non-zero exit code, iteration will be stopped and the exit code will be passed back to the console, as with a normal Symfony Command.

class MyProcessCommand extends BackgroundCommand
{
    // ...
    
    protected function execute(InputInterface $input, OutputInterface $output): int
    {
        $isInputValid = $this->someValidationChecks($input);
        if ($isInputValid === false) {
            $output->writeln('Message explaining invalid input');
            return 1;
        }
        
        // do some work
        
        return 0;
    }
}

Lifecycle Methods

The background command has additional methods that get called when the process starts and finishes. Useful for any initialising or final cleanup.

• onStart(InputInterface $input, OutputInterface $output): void
  • Similar to standard initialize(); useful for DaemonCommand.
• onShutdown(InputInterface $input, OutputInterface $output): void
• onException(\Exception $e, InputInterface $input, OutputInterface $output): void

class MyProcessCommand extends BackgroundCommand
{
    // ...
    
    protected function onShutdown(InputInterface $input, OutputInterface $output): void
    {
        $output->writeln('onShutdown method called.');
    }
}

Daemon Command

Basic Usage

Apart from extending a different class, the Daemon Command looks and works in a similar way to the Background Command. The PID file argument is optional. If it is not specified the process generates it's own PID file based on the command name.

<?php

declare(strict_types=1);

use Phlib\Console\Command\DaemonCommand;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Output\OutputInterface;

class MyProcessCommand extends DaemonCommand
{
    protected function configure()
    {
        $this->setName('my:process')
            ->setDescription('My background process.');
    }

    protected function execute(InputInterface $input, OutputInterface $output)
    {
        $output->writeln('Doing important work!');
    }
}

Output

Once a daemon process is detached, the original output is also lost. The --child-log | -o option can be used to specify a filename to write output. Alternatively, the createChildOutput() method can be overridden to return a new output instance. For example:

use Symfony\Component\Console\Output\StreamOutput;

class MyProcessCommand extends DaemonCommand
{
    // ... 
    
    protected function createChildOutput()
    {
        return new MyOutputToLoggerClass();
    }
}

Lifecycle Methods

The daemon command has additional methods, to the standard Symfony command methods and the background command, which gets called during the process lifecycle. The following example demonstrates overriding the methods.

class MyProcessCommand extends DaemonCommand
{
    // ...

    protected function onBeforeDaemonize(InputInterface $input, OutputInterface $output)
    {
        $output->writeln('onBeforeDaemonize method called.');
    }

    protected function onAfterDaemonizeChild(InputInterface $input, OutputInterface $output)
    {
        $output->writeln('onAfterDaemonizeChild method called.');
    }

    protected function onAfterDaemonizeParent(InputInterface $input, OutputInterface $output)
    {
        $output->writeln('onAfterDaemonizeParent method called.');
    }
    
    protected function onStart(InputInterface $input, OutputInterface $output): void
    {
        // Similar to `onAfterDaemonizeChild()` but also called if `--daemonize` option is not set.
        $output->writeln('onStart method called.');
    }
}

Command Line

# path/to/my/process start -d

# path/to/my/process status

# path/to/my/process stop

Options

Name	Short	Type	Required	Default	Description
action		Argument	yes		start, stop, status
daemonize	d	Option	no	no	Detaches the process
pid-file	p	Option	no	auto	Name of the PID file to use. Not used if daemonize is not set.
child-log	o	Option	no	no	Name of the file to save child output. Not used if daemonize is not set.

License

This package is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this program. If not, see http://www.gnu.org/licenses/.