Reliable Queue 
A PHP library for reliable queueing backed by Redis., (*1)
Current version: 0.4.0
Supported PHP versions: 5.3, 5.4, 5.5, 5.6, 7, (*2)
Installation
$ composer require altmetric/reliable-queue
Usage
<?php
use Altmetric\ReliableQueue;
use Altmetric\ChunkedReliableQueue;
use Altmetric\PriorityReliableQueue;
$queue = new ReliableQueue('unique-worker-name', 'to-do-queue', $redis, $logger);
$queue[] = 'some-work';
$queue[] = 'some-more-work';
foreach ($queue as $work) {
// Perform some action on each piece of work in the to-do-queue
}
$queue = new ChunkedReliableQueue('unique-worker-name', 100, 'to-do-queue', $redis, $logger);
foreach ($queue as $chunk) {
// $chunk will be an array of up to 100 pieces of work
}
$queue = new PriorityReliableQueue('unique-worker-name', array('critical-queue', 'default-queue', 'low-priority-queue'), $redis, $logger);
foreach ($queue as $name => $work) {
// $work will be popped from the queue $name in the priority order given
}
API Documentation
public ReliableQueue::__construct(string $name, string $queue, Redis $redis, LoggerInterface $logger)
$queue = new \Altmetric\ReliableQueue('unique-worker-name', 'to-do-queue', $redis, $logger);
Instantiate a new reliable queue object with the following arguments:, (*3)
-
$name: a unique string name for this worker so that we can pick up any
unfinished work in the event of a crash;
-
$queue: the string key of the list in Redis to use as the queue;
-
$redis: a Redis client object for
communication with Redis;
-
$logger: a
Psr\Log\LoggerInterface-compliant
logger.
The returned object implements both the
Iterator (and therefore
Traversable) and
ArrayAccess interface in
PHP., (*4)
This means that it can be iterated over with foreach, yielding the queue name
and a value on every iteration. Internally, the library will block for new work
but this is invisible from a client's perspective., (*5)
foreach ($queue as $key => $work) {
// $key will be the queue key name in Redis
// $work will be the value popped from the queue
}
You can also modify the queue as if it were an array by using the typical array
operations:, (*6)
$queue[] = 'work'; // enqueues work
$queue[1]; // returns work at index 1 if it exists
$queue[1] = 'work'; // sets work to index 1 in the queue
unset($queue[1]); // remove work at index 1 from the queue
public ChunkedReliableQueue::__construct(string $name, int $size, string $queue, Redis $redis, LoggerInterface $logger)
$queue = new \Altmetric\ChunkedReliableQueue('unique-worker-name', 100, 'to-do-queue', $redis, $logger);
Instantiate a new chunked, reliable queue object with the following arguments:, (*7)
-
$name: a unique string name for this worker so that we can pick up any
unfinished work in the event of a crash;
-
$size: an integer maximum size of chunk to return on each iteration;
-
$queue: the string key of the list in Redis to use as the queue;
-
$redis: a Redis client object for
communication with Redis;
-
$logger: a
Psr\Log\LoggerInterface-compliant
logger.
The returned object implements the
Iterator (and therefore
Traversable) interface in
PHP., (*8)
This means that it can be iterated over with foreach, yielding the queue name
and an array of up to $size elements on every iteration. Internally, the
library will block for new work but this is invisible from a client's
perspective., (*9)
If the queue contains sufficient items, the chunk of work will contain at most
$size elements but if there is not enough work, it may return less (but
always at least 1 value)., (*10)
public PriorityReliableQueue:__construct(string $name, array $queues, Redis $redis, LoggerInterface $logger)
$queue = new \Altmetric\PriorityReliableQueue('unique-worker-name', array('critical-queue', 'default-queue', 'low-priority-queue'), $redis, $logger);
Instantiate a new priority-ordered, reliable queue object with the following arguments:, (*11)
-
$name: a unique string name for this worker so that we can pick up any unfinished work in the event of a crash;
-
$queues: an array of string keys of lists in Redis to use as queues given in priority order;
-
$redis: a Redis client object for communication with Redis;
-
$logger: a
Psr\Log\LoggerInterface-compliant
logger.
The returned object implements the
Iterator (and therefore
Traversable) interface in
PHP., (*12)
This means that it can be iterated over with foreach, yielding the queue name
and a value on every iteration. Queues will be checked randomly for work based
on their priority order given in $queues meaning that the first queue will be
checked more often than the second, the second more than the third and so on.
Internally, the library will repeatedly poll for new work but this is invisible
from a client's perspective., (*13)
foreach ($queue as $key => $work) {
// $key will be the queue key name in Redis
// $work will be the value popped from the queue
}
References
Acknowledgements
- Thanks to James Adam for suggesting a way to
test the randomness of the priority queue.
License
Copyright © 2016-2017 Altmetric LLP, (*14)
Distributed under the MIT License., (*15)
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