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<?php
/**
* Copyright 2012-2014 Rackspace US, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
namespace OpenCloud\Queues;
use Guzzle\Common\Event;
use Guzzle\Http\Exception\BadResponseException;
use OpenCloud\Common\Exceptions\InvalidArgumentError;
use OpenCloud\Common\Service\CatalogService;
use OpenCloud\Queues\Resource\Queue;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
/**
* Cloud Queues is an open source, scalable, and highly available message and
* notifications service. Users of this service can create and manage a
* "producer-consumer" or a "publisher-subscriber" model from one simple API. It
* is made up of a few basic components: queues, messages, claims, and stats.
*
* In the producer-consumer model, users create queues where producers
* can post messages. Workers, or consumers, may then claim those messages and
* delete them once complete. A single claim may contain multiple messages, and
* administrators are given the ability to query claims for status.
*
* In the publisher-subscriber model, messages are posted to a queue like above,
* but messages are never claimed. Instead, subscribers, or watchers, simply
* send GET requests to pull all messages since their last request. In this
* model, a message will remain in the queue, unclaimed, until the message's
* time to live (TTL) has expired.
*
* Here is an overview of the Cloud Queues workflow:
*
* 1. You create a queue to which producers post messages.
*
* 2. Producers post messages to the queue.
*
* 3. Workers claim messages from the queue, complete the work in that message,
* and delete the message.
*
* 4. If a worker plans to be offline before its message completes, the worker
* can retire the claim TTL, putting the message back into the queue for
* another worker to claim.
*
* 5. Subscribers monitor the claims of these queues to keep track of activity
* and help troubleshoot if things go wrong.
*
* For the majority of use cases, Cloud Queues itself will not be responsible
* for the ordering of messages. If there is only a single producer, however,
* Cloud Queueing guarantees that messages are handled in a First In, First Out
* (FIFO) order.
*/
class Service extends CatalogService implements EventSubscriberInterface
{
const DEFAULT_TYPE = 'rax:queues';
const DEFAULT_NAME = 'cloudQueues';
public static function getSubscribedEvents()
{
return array(
'request.before_send' => 'appendClientIdToRequest'
);
}
/**
* Set the Client-ID header to all requests for this service.
*
* @param Event $event
*/
public function appendClientIdToRequest(Event $event)
{
$event['request']->setHeader('Client-ID', $this->getClientId());
}
/**
* An arbitrary string used to differentiate your worker/subscriber. This is
* needed, for example, when you return back a list of messages and want to
* know the ones your worker is processing.
*
* @var string
*/
private $clientId;
/**
* @param null $clientId
* @return $this
*/
public function setClientId($clientId = null)
{
if (!$clientId) {
$clientId = self::generateUuid();
}
$this->clientId = $clientId;
return $this;
}
/**
* @return string
*/
public function getClientId()
{
return $this->clientId;
}
/**
* Create a new Queue.
*
* @param string $name Name of the new queue
*
* @throws InvalidArgumentError
*
* @return Queue
*/
public function createQueue($name)
{
if (!is_string($name)) {
throw new InvalidArgumentError(
'The only parameter required to create a Queue is a string name. Metadata can be set with '
. 'Queue::setMetadata and Queue::saveMetadata'
);
}
$queue = $this->getQueue();
$queue->setName($name);
// send the request
$this->getClient()->put($queue->getUrl())->send();
return $queue;
}
/**
* This operation lists queues for the project, sorting the queues
* alphabetically by name.
*
* @param array $params An associative array of optional parameters:
*
* - marker (string) Specifies the name of the last queue received in a
* previous request, or none to get the first page of
* results. Optional.
*
* - limit (integer) Specifies up to 20 (the default, but configurable)
* queues to return. Optional.
*
* - detailed (bool) Determines whether queue metadata is included in the
* response. Optional.
*
* @return Collection
*/
public function listQueues(array $params = array())
{
return $this->resourceList('Queue', $this->getUrl('queues', $params));
}
/**
* Return an empty Queue.md object.
*
* @return Queue
*/
public function getQueue($id = null)
{
return $this->resource('Queue', $id);
}
/**
* This operation checks to see if the specified queue exists.
*
* @param string $name The queue name that you want to check
* @return bool
*/
public function hasQueue($name)
{
if (!$name || !is_string($name)) {
throw new InvalidArgumentError(sprintf(
'You must provide a queue name as a valid string. You provided: %s',
print_r($name, true)
));
}
try {
$url = $this->getUrl();
$url->addPath('queues')->addPath($name);
$this->getClient()->head($url)->send();
return true;
} catch (BadResponseException $e) {
return false;
}
}
}