eda-ha

mglantz.eda-ha

A role which provides high availability for an Event Driven Ansible (EDA) server. It requires you to setup two or more independent EDA servers and put a load balancer infront of them. Load balancer needs to do active-passive balancing between your EDA servers, meaning that B only gets traffic if A fails, etc.

Rulebooks running in the EDA server triggers playbooks exposed as job_templates in your AAP Controllers. As you create the playbooks which performs your actions - you include this role as shown in the example and depend tasks in the playbooks on the provided eda_activation boolean. If this boolean is true, that means the EDA server in question is active, if it's not, it means it's passive and no tasks should be run. So actions are only taken when an EDA server is "activated", meaning, the one getting load balanced to.

Fail-over between active and passive will be at the speed that the load balancer detects an outage, normally around a second. This is as the only difference between EDA Server A and B and corresponding AAP Controllers, is that tasks only get executed when triggered from the active EDA server. No configuration differs on the EDA server side.

Once you have read through below documentation and look at the role's tasks/main.yml, below picture will make sense. See architectural overview on GitHub if broken

Install role using:

ansible-galaxy role install mglantz.eda-ha

To use this role in your playbooks, create a requirements.yml file which you put in your roles directory. The requirements.yml file needs to state:

---    
- name: mglantz.eda-ha

Example of this can be seen here: https://github.com/mglantz/event-driven-ansible-demo/

Requirements

Two or more installed instance of Red Hat Ansible Automation Platform 2.4 with EDA controller, or perhaps https://github.com/ansible/eda-server (upstream eda-server has not been tested though).
A load balancer, configured to do active-passive load balancing to the installed EDA servers.
Create the file: /var/lib/ansible-automation-platform/eda/ui/static/media/detect.json on each EDA server, as follows:

{
   "install_id": "unique_id_that_you_make_up_fqdn_perhaps"
}

When the role assertains which EDA server is active and which ones are passive, it does so by matching the install_id it finds when contacting an EDA server directly and the one it finds when going via the load balancer.

Adjusted action taking playbooks as in the Example Playbook section below, which makes use of this role.

Role Variables

# domain name of load balancer in front of EDA servers
load_balancer_fqdn: <string|fqdn of load balancer> 

# domain name of eda server, suggestion, if AAP, set in job_template
eda_fqdn: <string|fqdn of eda server>

# if we are to validate https certificate. if set to true, all EDA servers needs to have valid certs
# also includes connection via load balancer
validate_eda_tls_cert: <bool|true/false>

Dependencies

Ansible 2.9 or 2.14.

Example Playbook

An example of how to use the role. In the action taking playbooks, the ones triggered by EDA events, adjust them as follows:

---
# Below play needs to be in the top of your playbooks.
# It makes sense to set the eda_fqdn variable on the job_template level
- name: Detect which EDA server is active and set eda_activation accordingly
  hosts: localhost
  roles:
    - { role: mglantz.eda-ha, load_balancer_fqdn: "loadbalancer.sudo.net", eda_fqdn: "eda.sudo.net" }

- name: Site is up
  hosts: all
  vars:
# Below variable needs to be added to the play which does your actual actions
    eda_activation: "{{ hostvars['localhost']['eda_activation'] }}"
  gather_facts: false
  tasks:
    - debug:
        msg: "All is up and well"
# Add below when statement for task that you want to control
      when: eda_activation

# Or similiar for a block
    - block: 
      - name: Do something else
        ansible.builtin.debug:
          msg: "Imaginary something else"
      - name: Also do this
        ansible.builtin.debug:
          msg: "Also this thing (imaginary)"
      when: eda_activation