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Ansible playbooks

This directory contains the Ansible playbooks used to configure the servers managed by the Rust Infrastructure team.

Executing a playbook

To execute a playbook you'll need to have Python 3 installed on the local machine and, if the environment requires it, AWS credentials. Then you can execute this command:

./apply <environment> <playbook>

For example:

./apply prod monitoring

The playbook is the name of a file inside the playbooks/ directory without the extension.

Executing a playbook on a new server

By default the ./apply script uses your current username to connect to the server, but that might not be present the first time you want to execute a playbook on a new server. You can override the user by passing the -u flag to the ./apply script followed by the username you want to use:

./apply <environment> <playbook> -u <username>

Permissions

In order to run the ./apply script, you need SSH permissions for the user on the host. If the host does not already have a public key for the given user, you can consider temporarily pushing one to the host using the AWS CLI.

aws ec2-instance-connect send-ssh-public-key \
    --instance-id $HOST_INSTANCE_ID \
    --instance-os-user $USER \
    --ssh-public-key file://$PATH_TO_PUBLIC_KEY

You will then have 60 seconds to kick off the ./apply script before the public key is removed again.

Environments

Making changes directly on production is not a great idea: to ease local development the ./apply script supports "environments". An environment is a subdirectory inside envs/ that contains an hosts file and optionally some variables inside group_vars.

At the moment the only working environment present in the repository is prod, which points to our production servers. To run a playbook on it you'll have to be a member of the infrastructure team with proper access.

The dev-example environment instead is a dummy one with all the hostnames and credentials replaced with dummy data. For local development is recommended to copy it to envs/dev (which is properly gitignored) and replace everything with your local development credentials. Everyone should be able to do it.

Note: environments are not an Ansible feature, they're fully implemented in the ./apply script.

Overview of the configuration

Playbooks

A playbook is a list of roles to apply to a group of servers with some configuration attached to them. If you need to tweak a setting in a server's configuration you'll probably just need to tweak the playbook.

Playbooks live in the playbooks/ directory.

Roles

A role is an isolated entity that contains all the necessary resources to deploy and configure a service in a server. Roles can't be applied directly but they need to be added to a playbook.

Roles live in the roles/ directory, and each of them has its own README.

Variables

Variables contain configuration values that change between environments or that are shared between multiple playbooks. Global variables are loaded from multiple files, and can be overridden by the next file loaded. The order is the following:

  • envs/<env>/group_vars/all.yml
  • group_vars/all.yml
  • envs/<env>/group_vars/<group>.yml
  • group_vars/<group>.yml

Resources