Chapter 1. Overview

Rackspace Cloud Queues is an open source, scalable, and highly available message and notifications service. Cloud Queues supports a variety of messaging patterns. Users of this service can create and manage a producer-consumer or a publisher-subscriber model (Section 2.2, “Messaging patterns”) from one simple API. Unlimited queues and messages give Cloud Queues users the flexibility they need to create powerful web applications in the cloud.

Cloud Queues is based on the OpenStack Marconi project.

Cloud Queues consists of a few basic components: queues, messages, claims, and statistics. In the producer-consumer model, users create queues in which producers, or servers, can post messages. Workers, or consumers, can then claim those messages and delete them after they complete the actions associated with the messages. A single claim can contain multiple messages, and administrators can query claims for status.

In the publisher-subscriber model, messages are posted to a queue as in the producer-consumer model, but messages are never claimed. Instead, subscribers, or watchers, send GET requests to pull all messages that have been posted since their last request. In this model, a message remains in the queue, unclaimed, until the message's time to live (TTL) has expired.

In both of these models, administrators can get queue statistics that display the most recent and oldest messages, the number of unclaimed messages, and more.

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