OpenStack里数据采集（监控数据、计费数据）基础设施--Ceilometer

问题导读：

1.Ceilometer是什么？

2.Ceilometer的组成是什么？

3.Agent的作用是什么？

4.Collector负责什么？

Ceilometer项目创建时最初的目的是实现一个能为计费系统采集数据的框架。在G版的开发中，社区已经更新了他们的目标，新目标是希望Ceilometer成为OpenStack里数据采集（监控数据、计费数据）的唯一基础设施，采集到的数据提供给监控、计费、面板等项目使用。

Project Goal

For Grizzly, the new objective is The project aims to become the infrastructure to collect measurements within OpenStack so that no two agents would need to be written to collect the same data. It’s primary targets are monitoring and metering, but the framework should be easily expandable to collect for other needs. To that effect, Ceilometer should be able to share collected data with a variety of consumers.

In the 0.1 (folsom) release its goal was just to deliver a unique point of contact for billing systems to aquire all meters they need to establish customer billing, across all current and futureOpenStack core components.

Wiki地址：https://wiki.openstack.org/wiki/Ceilometer
代码地址：https://github.com/openstack/ceilometer
文档地址：http://docs.openstack.org/developer/ceilometer/

社区现状

目前Ceilometer项目有11000+ lines代码，16位贡献者，最近的活跃贡献者有7位。社区的Roadmap如下：

v1 delivered with Folsom with all functions required to collect base metering info and provide standard API access
v2 delivered with G as an incubated project with (subject to variation)
End-User API access to own metering information
Integration of information summary as an Horizon plugin
New agents for other OpenStack components (Quantum Engines? Heat? etc…)
Multi publisher to handle other usage for data collection
Individual frequency per meter
Move to core for H

Ceilometer架构介绍

Ceilometer项目主要由Agent，Collector，DataStore，API和消息队列组成。

Agent

Agent的主要职责是周期性的从它管理的Plugin中轮询，触发查询，Plugin中有具体获取数据的逻辑。Ceilometer中的Agent分为Central Agent和Compute Agent。
Central Agent负责管理除了Compute（Nova）之外所有的Plugin，例如Swift，Cinder的Plugin。这些Plugin通过RPC调用相关服务的API并获取数据，然后将数据publish到Message Queue。Central Agent作为一个中心的数据采集调度器，之需要部署一个即可。
Compute Agent负责Compute节点的数据采集，在每一个Compute节点都需要部署一个Compute Agent。它一方主要负责周期性的采集Compute相关的数据并发布到MQ。
目前所规划的监控指标：http://docs.openstack.org/developer/ceilometer/measurements.html

Plugin

Ceilometer实现的Plugin框架依赖setuptools的Dynamic Discovery of Services and Plugins实现。这是Ceilometer能进行扩展的基础。Ceilometer中有四种类型的Plugin：Poller，Publisher，Notification和Transformer。