Kubectl Hooks

Hook Generator

To generator a starter hook:

$ kubes new hook kubectl
      create  .kubes/config/hooks/kubectl.rb

You can use hooks to run scripts at any part of the kubectl commands. Here’s an example of running a script before and after the kubectl apply command for the web/deployment resource.

.kubes/config/hooks/kubectl.rb

before("apply",
  on: "web/deployment",
  execute: "echo 'before apply hook test'",
)

after("delete",
  on: "web/deployment",
  execute: "echo 'after delete hook test'",
)

on option

The on option is important. If it is not set, then the hook script will run on every kubectl command. So given this hook definition:

before("apply",
  # Note how the on option is not set
  execute: "echo 'before apply hook test'",
)

With these resource definition files:

.kubes/resources/shared/namespace.yaml
.kubes/resources/web/deployment.yaml
.kubes/resources/web/web.yaml

The hook script will run 3 times.

$ kubes apply
# before apply hook test <= HERE 1
=> kubectl apply -f .kubes/output/shared/namespace.yaml
# before apply hook test <= HERE 2
=> kubectl apply -f .kubes/output/web/service.yaml
# before apply hook test <= HERE 3
=> kubectl apply -f .kubes/output/web/deployment.yaml
$

This is probably not what you want. So it is important to use the on option to scope when to run your hook like so:

before("apply",
  on: "web/deployment",
  execute: "echo 'before apply hook test'",
)

The hook script will run 1 time for the .kubes/resources/web/deployment.yaml:

$ kubes apply
=> kubectl apply -f .kubes/output/shared/namespace.yaml
=> kubectl apply -f .kubes/output/web/service.yaml
# before apply hook test <= HERE
=> kubectl apply -f .kubes/output/web/deployment.yaml
$

The on option is used to match the path the gets applied: .kubes/resources/web/deployment.yaml

exit on fail

By default, if the hook commands fail, then kubes will exit with the original hook error code. You can change this behavior with the exit_on_fail option.

before("apply"
  on: "web/deployment",
  execute: "/command/will/fail/but/will/continue",
  exit_on_fail: false,
)

General Form

before(COMMAND_NAME, OPTIONS)

The command name corresponds to the kubectl commands: apply, delete, etc.

Hook Options

Name	Description
label	A human-friendly label so you can see what hooks is being run.
execute	The script or command to run. IE: path/to/some/script.sh
exit_on_fail	Whether or not to continue process if the script returns an failed exit code.
on	What resource to run the hook on. IE: shared/namespace, web/deployment, web/service. Note: This option is only used by kubectl hooks.

Ruby Hooks

Instead of using a script for the hook execute option, you can also use a Ruby object. This provides some more control over the current process. See: Ruby Hooks

Getting Started

Docs