Poller
Poller is a library designed for polling non-blocking stuff., (*1)
, (*2)
Prerequisites
It's not a very common task for PHP but sometimes you really need to poll some things until they answer you something., (*3)
For example you can run other processes in the background and wait until they finish (you can use
poller-symfony-process
package for it to work with Symfony's Process component) or you can poll sockets or streams., (*4)
How to use
Suppose you have 10 processes that you need to run and you need to have only 3 processes running at the same time (only 3 job slots).
To implement this you will need to write an implementation of Poller\Task\Task interface which will represent a single process or
you can use already implemented ProcessTask from poller-symfony-process
package., (*5)
This way you will just need to instantiate a new Poller\Task\TaskQueue and enqueue all your tasks in it., (*6)
``` php
$tasksQueue = new TaskQueue();
$tasksQueue->enqueue(new ProcessTask(new Process("command to execute")));, (*7)
Now you need to create a new Poller instance and pass it your queue object and how many tasks do you want to run simultaneously
(how many job slots do you have):
``` php
$poller = new Poller($tasksQueue, 3);
And now you're ready to run the Poller:, (*8)
``` php
$poller->run();, (*9)
### Task events
You can also use events on Poller, we have:
``` php
Poller::EVENT_TASK_STARTED_PRE
Poller::EVENT_TASK_STARTED_POST
Poller::EVENT_TASK_FINISHED
Poller::EVENT_TASK_TERMINATED_PRE
Poller::EVENT_TASK_TERMINATED_POST
You can attach your listeners using attachListener method, f.e.:, (*10)
``` php
$poller->attachListener(Poller::EVENT_TASK_STARTED_PRE, function ($eventName, NamedTask $task) {
echo "Task ", $task->getName(), " is gonna be started!", "\n";
});, (*11)
$poller->attachListener(Poller::EVENT_TASK_FINISHED, function ($eventName, NamedTask $task) {
echo "Task ", $task->getName(), " was finished!", "\n";
});, (*12)
## Tasks queue
As you already saw, Poller needs TaskQueue to get tasks from. But TaskQueue class that comes with Poller is pretty limited
in a way that it's just a wrapper of SplQueue and it's not very extendable. What if, for example, you want to create a process
that runs some tasks forever? The best case using TaskQueue could be adding new tasks on `finish` event, but it wouldn't be very
readable.
Actually Poller accepts anything that implements `Poller\Task\PollerTaskQueue` interface. So you can easily implement infinite
queue:
``` php
use Poller\Task\PollerTaskQueue;
class InfiniteTaskQueue implements PollerTaskQueue
{
public function isEmpty()
{
return false;
}
public function dequeue()
{
return new YourOwnTask();
}
}
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