Deleting queues in RabbitMQ

queuerabbitmq

I have a few queues running with RabbitMQ. A few of them are of no use now, how can I delete them? Unfortunately I had not set the auto_delete option.

If I set it now, will it be deleted?

Is there a way to delete those queues now?

Best Answer

If you do not care about the data in management database; i.e. users, vhosts, messages etc., and neither about other queues, then you can reset via commandline by running the following commands in order:

WARNING: In addition to the queues, this will also remove any users and vhosts, you have configured on your RabbitMQ server; and will delete any persistent messages

rabbitmqctl stop_app
rabbitmqctl reset
rabbitmqctl start_app

The rabbitmq documentation says that the reset command:

Returns a RabbitMQ node to its virgin state.

Removes the node from any cluster it belongs to, removes all data from the management database, such as configured users and vhosts, and deletes all persistent messages.

So, be careful using it.

Related Solutions

Postgresql – Why do we need message brokers like RabbitMQ over a database like PostgreSQL

Rabbit's queues reside in memory and will therefore be much faster than implementing this in a database. A (good)dedicated message queue should also provide essential queuing related features such as throttling/flow control, and the ability to choose different routing algorithms, to name a couple(rabbit provides these and more). Depending on the size of your project, you may also want the message passing component separate from your database, so that if one component experiences heavy load, it need not hinder the other's operation.

As for the problems you mentioned:

polling keeping the database busy and low performing: Using Rabbitmq, producers can push updates to consumers which is far more performant than polling. Data is simply sent to the consumer when it needs to be, eliminating the need for wasteful checks.
locking of the table -> again low performing: There is no table to lock :P
millions of rows of task -> again polling is low performing: As mentioned above, Rabbitmq will operate faster as it resides RAM, and provides flow control. If needed, it can also use the disk to temporarily store messages if it runs out of RAM. After 2.0, Rabbit has significantly improved on its RAM usage. Clustering options are also available.

In regards to AMQP, I would say a really cool feature is the "exchange", and the ability for it to route to other exchanges. This gives you more flexibility and enables you to create a wide array of elaborate routing typologies which can come in very handy when scaling. For a good example, see:

_{(source: springsource.com)}

and: http://blog.springsource.org/2011/04/01/routing-topologies-for-performance-and-scalability-with-rabbitmq/

Finally, in regards to Redis, yes, it can be used as a message broker, and can do well. However, Rabbitmq has more message queuing features than Redis, as rabbitmq was built from the ground up to be a full-featured enterprise-level dedicated message queue. Redis on the other hand was primarily created to be an in-memory key-value store(though it does much more than that now; its even referred to as a swiss army knife). Still, I've read/heard many people achieving good results with Redis for smaller sized projects, but haven't heard much about it in larger applications.

Here is an example of Redis being used in a long-polling chat implementation: http://eflorenzano.com/blog/2011/02/16/technology-behind-convore/

Java – RabbitMQ and relationship between channel and connection

A Connection represents a real TCP connection to the message broker, whereas a Channel is a virtual connection (AMQP connection) inside it. This way you can use as many (virtual) connections as you want inside your application without overloading the broker with TCP connections.
You can use one Channel for everything. However, if you have multiple threads, it's suggested to use a different Channel for each thread.

Channel thread-safety in Java Client API Guide:

Channel instances are safe for use by multiple threads. Requests into a Channel are serialized, with only one thread being able to run a command on the Channel at a time. Even so, applications should prefer using a Channel per thread instead of sharing the same Channel across multiple threads.

There is no direct relation between Channel and Queue. A Channel is used to send AMQP commands to the broker. This can be the creation of a queue or similar, but these concepts are not tied together.
Each Consumer runs in its own thread allocated from the consumer thread pool. If multiple Consumers are subscribed to the same Queue, the broker uses round-robin to distribute the messages between them equally. See Tutorial two: "Work Queues".

It is also possible to attach the same Consumer to multiple Queues. You can understand Consumers as callbacks. These are called everytime a message arrives on a Queue the Consumer is bound to. For the case of the Java Client, each Consumers has a method handleDelivery(...), which represents the callback method. What you typically do is, subclass DefaultConsumer and override handleDelivery(...). Note: If you attach the same Consumer instance to multiple queues, this method will be called by different threads. So take care of synchronization if necessary.

Best Answer

Related Solutions

Postgresql – Why do we need message brokers like RabbitMQ over a database like PostgreSQL

Java – RabbitMQ and relationship between channel and connection

Related Topic