How on PHP cancel consumer in RabbitMQ? - php

Question

I have next code:
<?php
// callback function for recive the message and canceling consumer
function consumer(\AMQPEnvelope $envelope, \AMQPQueue $queue)
{
$queue->ack($envelope->getDeliveryTag());
$queue->cancel($envelope->getCorrelationId());
echo "Message was recived and consumer will be canceled by consumer tag: {$envelope->getCorrelationId()}\n";
}
// generating uniqie exchange and queue
$correlationId = uniqid(str_replace('.', '', (string)microtime(TRUE)) . '_');
$queueName = "databus_response_{$correlationId}";
$consumerTag = "consumer_tag_{$correlationId}";
// establesh connection
$connection = new \AMQPConnection(array('host'=>'127.0.0.1', 'user'=>'guest', 'password'=>'guest'));
$connection->connect();
$channel = new \AMQPChannel($connection);
// declare exchange
$exchange = new \AMQPExchange($channel);
$exchange->setFlags(AMQP_AUTODELETE);
$exchange->setType(AMQP_EX_TYPE_TOPIC);
$exchange->setName($queueName);
$exchange->declareExchange();
// declare queue
$queue = new \AMQPQueue($channel);
$queue->setFlags(AMQP_EXCLUSIVE);
$queue->setName($queueName);
$queue->declareQueue();
$queue->bind($queueName, '#');
// publish message in exchange
$exchange->publish('Test message', NULL, AMQP_PASSIVE, array('correlation_id' => $consumerTag));
// run consumer for getting this echange and canceling consumer after recive the message
$queue->consume('consumer', AMQP_NOWAIT, $consumerTag);
How you can see, i send one message to queue, and run consumer on this queue. In consumer method, you can see, what i want stop consumer on this queue after reciving first message by "cancel" method, but consumer not stopped. What i do wrong?
AMQP PECL module version 1.2.0 from https://github.com/pdezwart/php-amqp/tree/v1.2.0
PHP 5.4.4-14+deb7u10 (cli)
Linux v270 3.2.0-4-amd64 #1 SMP Debian 3.2.54-2 x86_64 GNU/Linux

Answer 1

just return false from consumer callback when you want to stop consuming.
From AMQPQueue.php stub file:
The AMQPQueue::consume() will not return the processing thread back to
the PHP script until the callback function returns FALSE.
P.S.: sad to say that php-amqp extension still lack of good documentation, but you can always read method annotation in stub files or read a bit outdated documentation on official php site in Polish language here - http://www.php.net/manual/pl/book.amqp.php (don't worry, nobody translated it, so all sensitive doc is in English).

Answer 2

Nowadays in the php-amqplib v2.* world you can also call basic_cancel on your AMQPChannel object.
here is a great blog post about controlling the number of consumers and their ttl using this technique.