openstack/zaqar
Code Issues Proposed changes
949d496263
zaqar/doc/source/install/get_started.rst
wangxiyuan 13b85cc38f Refactor the doc tree 
This patch refactor zaqar doc according to
the doc-migration spec.

api, cli, configuration and reference should
be added in the next few patches if need.

Change-Id: I74a4949f4eace423c06ab6e8d95838df1f312d93
2017-07-19 10:12:28 +08:00

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Messaging service overview

The Message service is multi-tenant, fast, reliable, and scalable. It allows developers to share data between distributed application components performing different tasks, without losing messages or requiring each component to be always available.

The service features a RESTful API and a Websocket API, which developers can use to send messages between various components of their SaaS and mobile applications, by using a variety of communication patterns.

Key features

The Messaging service provides the following key features:

  • Choice between two communication transports. Both with Identity service 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 Identity service IDs.
  • Support for several common patterns including event broadcasting, task distribution, and point-to-point messaging.
  • Component-based architecture with support for custom back ends and message filters.
  • Efficient reference implementation with an eye toward low latency and high throughput (dependent on back end).
  • Highly-available and horizontally scalable.
  • Support for subscriptions to queues. Several notification types are available:
    • Email notifications
    • Webhook notifications
    • Websocket notifications

Layers of the Messaging service

The Messaging service has following layers:

  • The transport layer (Messaging application) which can provide these APIs:
    • HTTP RESTful API (via wsgi driver).
    • Websocket API (via websocket driver).
  • The storage layer which keeps all the data and metadata about queues and messages. It has two sub-layers:
    • The management store database (Catalog). Can be MongoDB database (or MongoDB replica-set) or SQL database.
    • The message store databases (Pools). Can be MongoDB database (or MongoDB replica-set) or Redis database.