HA Deployment

Overview

This section shows how to deploy Congress with High Availability (HA). Congress is divided to 2 parts in HA. First part is API and PolicyEngine Node which is replicated with Active-Active style. Another part is DataSource Node which is deployed with warm-standby style. Please see the HA Overview for details.

+-------------------------------------+      +--------------+
|       Load Balancer (eg. HAProxy)   | <----+ Push client  |
+----+-------------+-------------+----+      +--------------+
     |             |             |
PE   |        PE   |        PE   |        all+DSDs node
+---------+   +---------+   +---------+   +-----------------+
| +-----+ |   | +-----+ |   | +-----+ |   | +-----+ +-----+ |
| | API | |   | | API | |   | | API | |   | | DSD | | DSD | |
| +-----+ |   | +-----+ |   | +-----+ |   | +-----+ +-----+ |
| +-----+ |   | +-----+ |   | +-----+ |   | +-----+ +-----+ |
| | PE  | |   | | PE  | |   | | PE  | |   | | DSD | | DSD | |
| +-----+ |   | +-----+ |   | +-----+ |   | +-----+ +-----+ |
+---------+   +---------+   +---------+   +--------+--------+
     |             |             |                 |
     |             |             |                 |
     +--+----------+-------------+--------+--------+
        |                                 |
        |                                 |
+-------+----+   +------------------------+-----------------+
|  Oslo Msg  |   | DBs (policy, config, push data, exec log)|
+------------+   +------------------------------------------+

HA for API and Policy Engine Node

New config settings for setting the DSE node type:

• N (>=2 even okay) nodes of PE+API node

  $ python /usr/local/bin/congress-server --api --policy-engine --node-id=<api_unique_id>
  

• One single DSD node

  $ python /usr/local/bin/congress-server --datasources --node-id=<datasource_unique_id>
  

HA for DataSource Node

Nodes which DataSourceDriver runs on takes warm-standby style. Congress assumes cluster manager handles the active-standby cluster. In this document, we describe how to make HA of DataSourceDriver node by Pacemaker .

See the OpenStack High Availability Guide for general usage of Pacemaker and how to deploy Pacemaker cluster stack. The guide has some HA configuration for other OpenStack projects.

Prepare OCF resource agent

You need a custom Resource Agent (RA) for DataSoure Node HA. The custom RA is located in Congress repository, /path/to/congress/script/ocf/congress-datasource. Install the RA with following steps.

$ cd /usr/lib/ocf/resource.d
$ mkdir openstack
$ cd openstack
$ cp /path/to/congress/script/ocf/congress-datasource ./congress-datasource
$ chmod a+rx congress-datasource

Configure RA

You can now add the Pacemaker configuration for Congress DataSource Node resource. Connect to the Pacemaker cluster with the crm configure command and add the following cluster resources. After adding the resource make sure commit the change.

primitive ds-node ocf:openstack:congress-datasource \
   params config="/etc/congress/congress.conf" \
   node_id="datasource-node" \
   op monitor interval="30s" timeout="30s"

Make sure that all nodes in the cluster have same config file with same name and path since DataSource Node resource, ds-node, uses config file defined at config parameter to launch the resource.

The RA has following configurable parameters.

• config: a path of Congress’s config file
• node_id(Option): a node id of the datasource node. Default is “datasource-node”.
• binary(Option): a path of Congress binary Default is “/usr/local/bin/congress-server”.
• additional_parameters(Option): additional parameters of congress-server