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HOOKS.md

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Hooks

OpenShift Ansible allows for operators to execute custom tasks during specific operations through a system called hooks. Hooks allow operators to provide files defining tasks to execute before and/or after specific areas during upgrades. This can be very helpful to validate or modify custom infrastructure when upgrading RHEL nodes in OpenShift.

It is important to remember that when a hook fails the operation fails. This means a good hook can run multiple times and provide the same results. A great hook is idempotent.

Using Hooks

Hooks are defined in the hosts inventory file under the all:vars section.

Each hook should point to a yaml file which defines Ansible tasks. This file will be used as an include meaning that the file can not be a playbook but a set of tasks. Best practice suggests using absolute paths to the hook file to avoid any ambiguity.

Example inventory variables

[all:vars]
# <snip>
openshift_node_pre_cordon_hook=/usr/share/custom/pre_cordon.yml
openshift_node_pre_upgrade_hook=/usr/share/custom/pre_upgrade.yml
openshift_node_pre_uncordon_hook=/usr/share/custom/pre_uncordon.yml
openshift_node_post_upgrade_hook=/usr/share/custom/post_upgrade.yml
# <snip>

Hook files must be a yaml formatted file that defines a set of Ansible tasks. The file may not be a playbook.

Example hook task file

---
# Trivial example forcing an operator to ack the start of an upgrade
# file=/usr/share/custom/pre_cordon.yml

- name: note the start of a node upgrade
  debug:
    msg: "Node upgrade of {{ inventory_hostname }} is about to start"

- name: require an operator agree to start an upgrade
  pause:
    prompt: "Hit enter to start the node upgrade"

Available Upgrade Hooks

openshift_node_pre_cordon_hook

  • Runs before each node is cordoned.
  • This hook runs against each node in serial.
  • If a task needs to run against a different host, said task will need to use delegate_to or local_action.

openshift_node_pre_upgrade_hook

  • Runs after each node is cordoned but before it is upgraded.
  • This hook runs against each node in serial.
  • If a task needs to run against a different host, said task will need to use delegate_to or local_action.

openshift_node_pre_uncordon_hook

  • Runs after each node is upgraded but before it is uncordoned.
  • This hook runs against each node in serial.
  • If a task needs to run against a different host, said task will need to use delegate_to or local_action.

openshift_node_post_upgrade_hook

  • Runs after each node is uncordoned; it's the last node upgrade action.
  • This hook runs against each node in serial.
  • If a task needs to run against a different host, said task will need to use delegate_to or local_action.