[[s-glance-api]]
==== Highly available OpenStack Image API

OpenStack Image Service offers a service for discovering, registering, and retrieving virtual machine images.
Making the OpenStack Image API service highly available in active / passive mode involves

* configuring OpenStack Image to listen on the VIP address,
* managing OpenStack Image API daemon with the Pacemaker cluster manager,
* configuring OpenStack services to use this IP address.

NOTE: Here is the http://docs.openstack.org/trunk/install-guide/install/apt/content/ch_installing-openstack-image.html[documentation] for installing OpenStack Image API service.


===== Adding OpenStack Image API resource to Pacemaker

First of all, you need to download the resource agent to your system:
  
----
cd /usr/lib/ocf/resource.d/openstack
wget https://raw.github.com/madkiss/openstack-resource-agents/master/ocf/glance-api
chmod a+rx *
----

You may now proceed with adding the Pacemaker configuration for
OpenStack Image API resource. Connect to the Pacemaker cluster with +crm
configure+, and add the following cluster resources:

----
include::includes/pacemaker-glance_api.crm[]
----

This configuration creates

* +p_glance-api+, a resource for manage OpenStack Image API service

+crm configure+ supports batch input, so you may copy and paste the
above into your live pacemaker configuration, and then make changes as
required. For example, you may enter +edit p_ip_glance-api+ from the
+crm configure+ menu and edit the resource to match your preferred
virtual IP address.

Once completed, commit your configuration changes by entering +commit+
from the +crm configure+ menu. Pacemaker will then start the OpenStack Image API
service, and its dependent resources, on one of your nodes.

===== Configuring OpenStack Image API service

Edit +/etc/glance/glance-api.conf+:
----
# We have to use MySQL connection to store data:
sql_connection=mysql://glance:password@192.168.42.101/glance

# We bind OpenStack Image API to the VIP:
bind_host = 192.168.42.103

# Connect to OpenStack Image Registry service:
registry_host = 192.168.42.103

# We send notifications to High Available RabbitMQ:
notifier_strategy = rabbit
rabbit_host = 192.168.42.102
----


===== Configuring OpenStack Services to use High Available OpenStack Image API

Your OpenStack services must now point their OpenStack Image API configuration to
the highly available, virtual cluster IP address -- rather than an
OpenStack Image API server's physical IP address as you normally would.

For OpenStack Compute, for example, if your OpenStack Image API service IP address is
192.168.42.104 as in the configuration explained here, you would use
the following line in your +nova.conf+ file:

----
glance_api_servers = 192.168.42.103
----

You need also to create the OpenStack Image API Endpoint with this IP.

NOTE: If you are using both private and public IP addresses, you should create two Virtual IP addresses and define your endpoint like this:
----
keystone endpoint-create --region $KEYSTONE_REGION --service-id $service-id --publicurl 'http://PUBLIC_VIP:9292' --adminurl 'http://192.168.42.103:9292' --internalurl 'http://192.168.42.103:9292'
----