Openshift/K8 templating and deployment engine

Super simple python templating and deployment engine for openshift/k8 yml files. Detects changes made and only applies the required objects.

Use case

This tool was born in the need to a very simple templating system which can track changes (similar to terraform). It was build for my requirements but should fit others as well.

Requirements

• Python 3.8 or later
• oc (or kubectl) binary in path

Usage

Deploy all changes

Deploys all enabled app

python deploy.py deploy-all

Deploy single app

Deploys all object of the app with the give name

python deploy.py deploy nginx

Reload config

This command executes the on-config-change trigger

python deploy.py reload prometheus

Configuration

In OK8Deploy you define apps, each app can contain multiple yml files. Additionally, there is a project configuration which describes the openshift project.

All yml files will be pre-processed before they will be imported. This includes replacing any known ${KEY} variables with their associate values and merging referenced templates.

Config structure

configs
|- _root.yml <- Project config
|- my-app <- App
    |- _index.yml <- App config
    |- dc.yml <- Openshift yml file(s)
    |- secrets.yml

Project config

Here is a sample _root.yml file

project: 'my-oc-project'

# OPTIONAL STUFF
# Global variables
vars:
  DOMAIN: "dev-core.org"

App config

An app is represented by a folder containing an _index.yml file and any additional openshift yml files. The following shows all available parameters. Only the first 3 are required.

# The type defines how the app will be used.
# Can be "app" (default) or "template"
type: 'app'

# Indicates if this app should be deployed or ignored
enabled: true 

# Deployment config parameters
dc:
    # Name of the deployment config, available as variable, see below
    name: 'my-app'

# Template which should be applied, none by default
applyTemplates: []

# Templates which should be applied AFTER processing the other templates and base yml files
postApplyTemplates: []

# Action which should be executed if a configmap has been changed
on-config-change:
# Available options: 
# deploy (re-deploys the deployment config)
  - deploy

# exec (Executes a command inside the running container)
  - exec: 
      command: /bin/sh
      args: 
        - "-c"
        - "kill -HUP $(ps a | grep prometheus | grep -v grep | awk '{print $1}')"

# Additional variables which are used for replacements
vars:
  NSQ_NAME: 'nsq-core'

# Required parameters which must be passed to this app.
# This can be done via the CLI or if this app is a template the referring app can define it in "vars" 
params:
  - PASSWORD

# File based configmaps
configmaps:
  - name: nginx-config
    files:
      - file: "nginx.conf"

Configmaps

In addition to the regular configmaps you can also define configmaps with a file source. This is done in the _index.yml file:

configmaps:
  - name: nginx-config
    files:
      - file: "nginx.conf"

This will create a new configmap from the file nginx.conf with the name nginx-config. Any changes made to the file will be automatically deployed.

Variables

You can refer to variables in yml files by using ${VAR-NAME}. Variables can also be loaded from files.

# _index.yml
vars:
  # Regular key/value assignment
  key: value

  # This will load the public/private and intermediate certs
  # from a pem file and store it in *_KEY, *_PUBLIC, *_CACERT
  # where * is the key of the value (CERT in this example)
  CERT:
    loader: pem
    file: my-cert.pem

It is also possible to decorate objects using variables:

# _index.yml
vars:
  someMerging:
    hello: world
    replicas: 2

# dc.yml
spec:
  replicas: 1
  _ok8merge: ${someMerging}

Results in:

spec:
  replicas: 2
  hello: world

Global variables

The following variables are available anywhere inside the yml files by default

Key	Value
DC_NAME	Name of the deployment-config in the _index.yml
OC_PROJECT	Name of the openshift project in _root.yml

Templates

You can use templates to reuse and generate yml files. To do so you create a new app with the type field set to template. Other apps can now refer to this template via the applyTemplates or postApplyTemplates field. Templates can refer to other templates (recursively). Any vars defined are passed to the next template.

Example:

|- some-template
    |- _index.yml
    |- dc.yml

|- my-app
    |- _index.yml <-- Referes to "some-template"
    |- others.yml

Will result in

|- my-app
    |- _index.yml
    |- others.yml
    |- dc.yml

Object merging

The template engine support content aware object merging. This allows you to decorate existing templates or enhance apps with features. A common example would be a template which adds a monitoring sidecar container. In the examples you can find the nsq-template which defines a sidecar container.

Here is a minimal example:

# examples/nsq-template/dc.yml
kind: DeploymentConfig
apiVersion: v1
spec:
    template:
        spec:
        containers:
            - name: "nsqd"
            image: "nsqio/nsq"

# examples/my-app/dc.yml
kind: DeploymentConfig
apiVersion: v1
metadata:
  name: "${DC_NAME}"

spec:
  replicas: 1
  selector:
    name: "${DC_NAME}"
  strategy:
    type: Rolling

  template:
    metadata:
      labels:
        name: "${DC_NAME}"

    spec:
      containers:
        - name: "${DC_NAME}"
          image: "docker-registry.default.svc:5000/oc-project/my-app:prod"

If we now apply the nsq-template to our app using postApplyTemplates: [nsq-template] the DeploymentConfig object gets automatically merged:

# Merged result after applying template
kind: DeploymentConfig
apiVersion: v1
metadata:
  name: "${DC_NAME}"

spec:
  replicas: 1
  selector:
    name: "${DC_NAME}"
  strategy:
    type: Rolling

  template:
    metadata:
      labels:
        name: "${DC_NAME}"

    spec:
      containers:
        - name: "${DC_NAME}"
          image: "docker-registry.default.svc:5000/oc-project/my-app:prod"
        # This is the part of the template
        - name: "nsqd"
            image: "nsqio/nsq"

Loops

Loops allow you to apply the same template with different parameters. This is useful when deploying microservices which all have the same openshift config.

# _index.yml
enabled: true
applyTemplates: [ api-template ]
forEach: 
    # DC_NAME is required for each instance that should be created
  - DC_NAME: entity-compare-api
    # You can define other vars as well
    PORT: 8080

  - DC_NAME: favorite-api
    PORT: 8081

Library

It's possible to define whole project as a library. This allows all apps and templates to be reused by another project. An example would be the same setup for multiple systems which are separated by projects (e.g. dev/test/prod).

# testLib/_root.yml
type: library

# Required parameters
params:
  - domain
  - dockerDomain
  - imageStreamTag

# prod/_root.yml
project: 'prod-project'
inherit: testLib

# Required parameters
vars:
  domain: my-prod.dev-core.org
  dockerDomain: prod-docker.com
  imageStreamTag: prod

When you now deploy the prod project it will inherit all apps inside testLib.

Change tracking

Changes are detected by storing a md5 sum in the label of the object. If this hash has changed the whole object will be applied. If no label has been found in openshift the object is assumed to be equal, and the label is added.

Examples

All examples can be found in the examples folder.

Grafana

The grafana folder contains a basic grafana setup.

NSQ

This example adds an NSQ sidecar container to a deployment config.

my-app/_index.yml

enabled: true
postApplyTemplates: [nsq-template]
vars:
  NSQ_NAME: 'app-nsq'

dc:
  name: my-app

Contribute

The code should be mostly commented. If you found a bug or want to improve something feel free to open an issue and discuss your ideas.