We use a standard Ansible inventory file with some semantic conventions applied to Ansible groups. The semantic model applied to the Ansible inventory file is described in the following sections.
Ansible provides rich semantics for inventory files. We leverage the Ansible model by applying a semantic convention that is based on the Apigee Private Cloud domain model for referencing server nodes as collections of planets and regions. This means that Apigee semantics are used as group names to ascribe roles to normal Ansible inventory files. Please refer to the Ansible documentation for more information on how this works.
These roles depend on use of conventions in the inventory file. Specifically inventory file conventions are Ansible group names that are defined around Apigee semantics. These Ansible groups are semantically linked to the Apigee documentation. The Ansible groups of groups used as conventions correspond to the installation roles and server categorizations called out in the Apigee Private Cloud Installation and Configuration Guide. It has been useful to use planet and region designations combined with the documented installation role names to create categorization semantics that should be fairly intuitive once you read the Apigee Private Cloud Installation and Configuration Guide.
A planet refers to all server nodes across all data centers. These semantics are held via the use of group names for all nodes that fulfill a specific purpose. The installation roles provide the semantic model we followed. The inventory file group names for planet level semantics are listed in the template inventory file below.
A region represents a subset of a planet. The semantics used for installation roles are congruent with a region. Regions have been referenced as data centers. The internal configurations of OPDK and BaaS support many regions such as dc-1, dc-2 ... dc-n. Following this historical precedent we also define the regions with their corresponding installation role to provide a semantic model as follows:
# Listing that references all data centers that compose a planet. [planet] dc-1 [dc-1] # Listing of all nodes in data center 1 (dc-1) [ds:children] # Listing of all the Cassandra and Zookeeper nodes across the planet dc-1-ds [dc-1-ds] # Listing of all the Cassandra and Zookeeper nodes in dc-1 [dc-1-ms] # Listing of all the Management Server nodes in dc-1 [dc-1-ldap] # Listing of all OpenLDAP nodes in dc-1 [dc-1-rmp] # Listing of all Router and Message Processor nodes in dc-1 [dc-1-qpid] # Listing of all Qpid nodes in dc-1 [dc-1-pg] # Listing of all Postgres nodes in dc-1 [dc-1-pgmaster] # Listing of the single Postgres master node in dc-1 [dc-1-pgstandby] # Listing of the single Postgres standby node in dc-1 [dc-1-ui] # Listing of the UI node in dc-1
Zookeeper nodes can be designated as an observer node. Ansible inventory files allow variables to be assigned to servers. These roles will update the silent installation configuration file correctly for any zookeeper node that is assigned the variable zk_observer.
zk_observer=true
This is a sample of a configuration of a Zookeeper node as an observer. Assuming that the first three nodes listed are Cassandra/Zookeeper nodes then we can configure a node as a zookeeper observer as follows:
[planet] dc-1-n1 dc-1-n2 dc-1-n3 zk_observer=true [dc-1-ds] dc-1-n[1:3]
Cassandra nodes can be configured to be rackaware. This leverages the Cassandra built in functionality for managing itself when the Cassandra ring is distributed across several availability zones. We would set the variable rack for each member of the Cassandra ring with the designated location we want for that node in the following way:
rack=1,1
Please note that this follows the Cassandra rack aware configuration syntax:
rack=<Availability Zone>,<Position on Rack>
This is a sample of a configuration of Cassandra as a node that is rackaware. Assuming that the first three nodes listed are Cassandra/Zookeeper nodes then we can configure a node as rackaware as follows:
[planet] dc-1-n1 rack=1,1 dc-1-n2 rack=2,1 dc-1-n3 rack=3,1 [dc-1-ds] dc-1-n[1:3]