Running playbooks

The playbooks in this repo can conveniently be run either with the ansible-vagrant or ansible-ec2 scripts depending on whether the playbook should be run against the live environment or the Vagrant virtual one.

Playbook structure

The top-level playbook is site.yml. In theory, this playbook can be run to recreate the environment.

The site.yml playbook just includes lower-level playbooks from the playbook/ directory. The sub-playbooks are probably what you want for running various tasks in the cluster.

Sub-playbooks:

• create-gluster-ca.yml - Generates a Gluster CA key/cert. This is a one-time operation, and is just here to document the process. The actual CA key material for the production cluster is stored outside this repo.
• install-servers.yml - This installs the Gluster server onto all inventory hosts in the gluster-servers group. This should only need to be run when new servers are added to the inventory.
• gluster-volume.yml - This creates volumes (supervols) on the servers. The configuration for the volumes can be found in group_vars/gluster-servers. This playbook will not destroy an existing volume, but may modify it, so be careful when editing the gluster_volumes dict.

Inventory structure

The structure of the ansible groups is:

• gluster-servers // from inventory_groups
  • server cluster // from inventory_groups (e.g., us-east-2-c00)
    • server group // from ec2 tags (e.g., gluster-group=us-east-2-c00-g00)

The Gluster server ec2 instances each have a tag, gluster-group, applied to them to indicate which server group they are a part of. We are defining a server group as a set of 3 servers, each in a different AZ. A group will be used to create one or more replica 3 volumes. The ec2.py dynamic inventory script uses the tag to create a host group as: tag_gluster_group_us_east_2_c00_g00. We manually combine these dynamic groups into clusters and add the clusters to the overall gluster-servers group. Both of these are done in the inventory_groups file.

For each cluster, there is one instance that contains a tag designating it as the "cluster master." While not really a "master," it is used as the host for issuing gluster management cli commands. We do this instead of just run_once: true because we need to make sure we can correctly assemble a single cluster w/ peer probe, and the cli can have a locking problem w/ commands arriving from many hosts.

Vagrant environment

There is a vagrant environment in this repo that allows (manual) testing of the ansible playbooks. You will need to bring your own RHEL 7.4 Vagrant box, however. The Vagrantfile points to an initial ansible playbook and sets inventory variables such that the VMs should be in groups and configurable just like the corresponding AWS instances.

AWS environment

To properly run against AWS, you need to have your credentials set properly. The configuration assumes you have a boto profile named osio configured. Before trying to run the ansible scripts, run ec2.py by itself and ensure it returns suitable inventory information.

Adding hardware to the environment

When new instances are to be added to the AWS environment, the inventory files need to be adjusted to reflect how they should be grouped and configured.

If adding new servers, they should be tagged, as described above, with a server "group." Since servers are added in multiples of the group size (3), you will be adding a new group, most likely to an existing cluster. Just use the next available group number in the tag. If you decided to start a new cluster, be sure to tag one of the servers with the cluster-master tag. The new group (and cluster) need to be added to the inventory_groups file so that the group is part of the correct cluster and the (new) cluster is part of the overall gluster-servers. The servers will need to be registered via register-servers.yml and installed via playbooks/install-servers.yml. You will probably want to limit the hosts to the new group to speed things along when you run the playbook.

When adding additional volumes, that is done in the group_vars/gluster-servers file. This file contains the definition for all volumes in all clusters. Just add a new volume to the list here, specifying its size, the device to use, and the name of the server group it should be created in. The playbooks/gluster-volume.yml playbook can take it from there.