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gradle-swarm-composer

Plugin that provides utilities for assembling Docker compose configurations for use with Docker Compose or as Stacks for Docker Swarm mode.

Goals of this plugin are:

  • Support independent configurations for multiple deployments / setups for the same stack
  • Allow distributing configuration for both setups and stacks across multiple files for better maintainability
  • Support storing deployment specific configuration encrypted
  • Ensure that required configuration variables are set
  • Allow to easily extend an existing deployment configuration

Usage

buildscript {
  repositories {
    mavenCentral()
    maven {
      url 'https://artifactory.wetransform.to/artifactory/local'
    }
    maven {
      url "https://plugins.gradle.org/m2/"
    }
  }
  dependencies {
    classpath 'to.wetransform:gradle-swarm-composer:2.0.0'
  }
}

apply plugin: 'to.wetransform.swarm-composer'

Default project layout

root
│
├──stacks
│  ├──stack1
│  │  ├─ stack.yml
│  │  ├──builds
│  │  │  └──mycustom
│  │  │     └─ Dockerfile
│  │  └──config
│  │     ├─ config1.yml
│  │     ├─ config2.vault.yml
│  │     └─ config3.env
│  │
│  └──stack2
│     ├─ swarm-composer.yml
│     └─ stack.yml
│
└──setups
   ├──setup1
   │  ├─ swarm-composer.yml
   │  ├─ config1.yml
   │  └─ config2.env
   │
   └──setup2
      └─ config1.yml

Configuration

Individual configuration for swarm-composer regarding each setup can be done via the swarm-compose.yml file. Here are the currently supported options explained with an example:

# Swarm composer configuration
description: |
  Optional description of the setup for documentation purposes

# a setup may extend other setups to avoid duplicate configuration
extends:
  - other-setup
  - another-setup

# States that this setup creates a configuration compatible to Docker Compose
docker-compose: true

# Custom target file in project root
target-file: docker-compose.yml

Template variables

Configuration variables to be used in templates can be defined in .yml and .env files. YAML configurations are accessible via their property path (segments separated separated by dots), variables defined in environment files are available with the env. prefix.

TODO: Example file, Example for variable replacement, where can config files be placed, ...

TODO: Configuration that controls swarm-composer behavior (e.g. which modes are enabled, if another setup should be extended, if a custom file name should be used, etc.)

Restrictions for variable evaluation in configuration files: Simple value insertions/replacements work, for conditions only boolean variables are supported right now.

Secret variables

Sensible information like passwords can be stored in encrypted configuration files. These files then also for instance can be added to version control.

For encrypted configuration files right now only the YAML format is supported, variables must be string values.

To create an encrypted configuration file, first create its plain counterpart in the setup folder. The file names of the plain configuration files should end with .secret.yml.

You also need to provide the password to use for the encryption. It can be provided as Gradle property, either for all setups (vault_password) or for individual setups (vault_password_<setup>).

To encrypt the configuration file, run the encryption task for the respective setup (e.g. ./gradlew encrypt-<setup>). Encrypted vault files have a file name that ends with .vault.yml.

Note that when accessing the setup configuration, the plain files are recreated. If you want to remove them after a task, also add the purgeSecrets task.

If you want to edit a vault file, you can either add encrpyted entries there, or simply decrypt the file with the task decrypt-<setup> and encrypt it after you completed your changes.

Reserved variable names

Some variables are provided by swarm-composer and will override any variables you define with the same name:

  • stack - The name of the stack
  • setup - The name of the setup
  • builds - Under this key information on Docker images built individually for a setup can be found, for example builds.mycustom.image_tag