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Official name OpenStack Messaging
Source code https://github.com/openstack/zaqar
Bug tracker https://bugs.launchpad.net/zaqar
Feature tracker https://blueprints.launchpad.net/zaqar
Contributor documentation http://docs.openstack.org/developer/zaqar/

Python Zaqar Client

Source code https://github.com/openstack/python-zaqarclient
Bug tracker https://bugs.launchpad.net/python-zaqarclient
Feature tracker https://blueprints.launchpad.net/python-zaqarclient


Zaqar is a multi-tenant cloud messaging service for web and mobile developers. It combines the ideas pioneered by Amazon's SQS product with additional semantics to support event broadcasting.

The service features a fully RESTful API, which developers can use to send messages between various components of their SaaS and mobile applications, by using a variety of communication patterns. Underlying this API is an efficient messaging engine designed with scalability and security in mind.

Other OpenStack components can integrate with Zaqar to surface events to end users and to communicate with guest agents that run in the "over-cloud" layer. Cloud operators can leverage Zaqar to provide equivalents of SQS and SNS to their customers.

Key features

Zaqar provides the following key features:

  • Choice between two communication transports. Both with Keystone support:
    • Firewall-friendly, HTTP-based RESTful API
      • Many of today's developers prefer a more web-friendly HTTP API. They value the simplicity and transparency of the protocol, its firewall-friendly nature, and its huge ecosystem of tools, load balancers and proxies. In addition, cloud operators appreciate the scalability aspects of the REST architectural style.
    • Websocket-based API for persistent connections.
      • Websocket protocol provides communication over persistent connections. Unlike HTTP, where new connections are opened for each request/response pair, Websocket can transfer multiple requests/responses over single TCP connection. It saves much network traffic and minimizes delays.
  • Multi-tenant queues based on Keystone project IDs
  • Support for several common patterns including event broadcasting, task distribution, and point-to-point messaging (See Zaqar Use Cases)
  • Component-based architecture with support for custom backends and message filters
  • Efficient reference implementation with an eye toward low latency and high throughput (dependent on backend)
  • Highly-available and horizontally scalable (See Server Architecture)
  • Support for subscriptions to queues. Several notification types are available:
    • Email notifications
    • Webhook notifications
    • Websocket notifications

Project scope

The Zaqar API is data-oriented. That is, it does not provision message brokers and expose those directly to clients. Instead, the API acts as a bridge between the client and one or more backends. A provisioning service for message brokers—however useful—serves a somewhat different market from what Zaqar is targeting today. With that in mind, if users are interested in a broker provisioning service, the community should consider starting a new project to address that need.

Design principles

Zaqar, as with all OpenStack projects, is designed with the following guidelines in mind:

  • Component-based architecture. Quickly add new behaviors
  • Highly available and scalable. Scale to very serious workloads
  • Fault tolerant. Isolated processes avoid cascading failures
  • Recoverable. Failures should be easy to diagnose, debug, and rectify
  • Open standards. Be a reference implementation for a community-driven


Zaqar is production-ready for small and medium-sized workloads. The project is in production at Rackspace and other companies are in the process of deploying it in their own clouds. Support for the v2 APIs is available for Python in python-zaqarclient, and for other languages through Rackspace-supported SDKs.


Currently (during Mitaka release cycle) Zaqar team is reworking Zaqar documentation.

Zaqar Configuration Reference

Message service Configuration Reference

Zaqar Contributor Guide

Zaqar Contributor Guide

Zaqar RESTful API Specs

Other documentation

"Getting Started Guide", "Zaqar RESTful API v1.0 Guide and Reference" are currently not hosted anywhere, but you can generate these documents from Zaqar source code repository. Here's how to do it:

  1. Ensure you have maven and git programs installed on your system.
  2. Clone Zaqar repository in the preferred directory on your machine by executing git clone https://github.com/openstack/zaqar.git
  3. Inside cloned repository in doc/user-guide directory execute mvn clean generate-sources to generate documentation html files from sources.
  4. You can view documentation by opening generated html files in your browser:
    1. Getting Started Guide: doc/user-guide/zaqar-get-started/target/docbkx/webhelp/zaqar-get-started/index.html
    2. Zaqar Configuration Reference: doc/user-guide/zaqar-config-ref/target/docbkx/webhelp/zaqar-config-ref/index.html
    3. Zaqar API v1.0 Guide and Reference: doc/user-guide/zaqar-api-ref/target/docbkx/webhelp/zaqar-api-ref/index.html


The Zaqar team hangs out in #openstack-zaqar on Freenode. Feel free to stop in anytime to chat with us; the crew is always happy to hear your ideas and answer questions. If you run into a bug, please report it using our issue tracker.




  • Alejandro Cabrera. Rackspace Atlanta. Introducing Openstack Marconi. July 17, 2013. Youtube Speaker Deck
  • Flavio Percoco. EuroPython 2013. Marconi: Queuing and Notification Service for Openstack. July 2, 2013. YouTube
  • Kurt Griffiths, Allan Metts. Openstack Summit April 2013. Project Overview: OpenStack Queuing and Notification Service ("Marconi"). April 2013. YouTube
  • Kurt Griffiths, Flavio Percoco, Allan Metts. Openstack Summit November 2013. Openstack Queuing and Notification Service. November 2013. YouTube
  • Yeela Kaplan. EuroPython 2014. OpenStack Queuing and Notification Service ("Marconi"). July 22, 2014. YouTube



Information for Contributors

Zaqar Contributor Guide

Note: If you can't find the information you are looking for, please drop us a line in IRC (#openstack-zaqar) and we'll be happy to help.


Quality Engineering