marathon release

marathon-release allows you to manage multiple Marathon application definitions as a single release.

This utility allows you to define all the Marathon application definition that make up the release of your application landscape and handle environment specific variations.

You get to:

• keep the complete release under version control.
• deploy the same release to different environments.
• handle environment specific variations.
• detect configuration drift.
• keep your release in sync with the intended state.

marathon-release is a just a tiny bit of glue code between the Python:

• requests
• configparser
• jinja

Installation

If you want to install the utility natively, install Pipsi, then type:

git clone https://github.com/mvanholsteijn/marathon-release 
pipsi install marathon-release

Docker

If you want to run using the Docker image, just create an alias:

alias marathon-release='docker run -v $PWD:/release mvanholsteijn/marathon-release:latest'

directory layout

marathon-release expects the following directory layout:

.
├── cfg
|   ├── domain.cfg          # definition of different domains.
├── apps
|   ├── <app-id>.cfg        # environment specific configuration for <app-id>.
|   ├── <app-id>.json	    # Marathon application definition template for <app-id>.

The application definition files are Jinja templates which may refer to any properties that are defined in the configuration files (.cfg) which are standard Python configuration files.

Domain configuration

The domain configuration file in ./cfg/domain.cfg is required to define a property named marathon_url which points to Marathon application. For each environment there should be a separate section. The following example shows the definition for the domains dev, tst, acc and prd.

[DEFAULT]
marathon_url		=	http://marathon.%(external_domain_name)s:8080

[dev]
external_domain_name	=	dev.127.0.0.1.xip.io

[tst]
external_domain_name	=	test.127.0.0.1.xip.io

[acc]
external_domain_name	=	acc.127.0.0.1.xip.io

[prd]
external_domain_name	=	prd.127.0.0.1.xip.io

The domain configuration file can also be used to define any global variables which are applicable to all application definitions. In the above example, we have defined the global variable external_domain_name which is used in the definition of the required property marathon_url.

Application configuration

For each application you can define it Marathon application definition in ./apps/<app-id>.json. The app-id should match the marathon application id defined in the file.

Any environment specific properties can be defined in the file ./apps/<app-id>.json. The following example shows the configuration of the properties number_of_instances and release for the domains dev, tst, acc and prd.

[DEFAULT]
number_of_instances	=	1

[dev]
release			=	latest

[tst]
release			= 	1.6.9

[acc]
release			= 	1.6.8
number_of_instances	=	2

[prd]
release			= 	1.6.7
number_of_instances	=	4

As the application definition file is a Jinja you may refer to these and the properties defined in the domain configuration files, as show in the following snippet:

{
  "id": "/paas-monitor", 
  "mem": 16, 
  "cpus": 0.10, 
  "instances": {{number_of_instances}}, 
      ....
      "image": "mvanholsteijn/paas-monitor:{{release}}", 
   "labels" : {
     ...
     "HAPROXY_0_VHOST" : "paas-monitor.{{external_domain_name}}"
   }
}

Diffing a release

To determine what is going to happen, you can use the diff command:

$ marathon-release diff --domain-name dev 

INFO: loaded 1 applications from ./apps
INFO: deploying new application "/paas-monitor"

Deploying a release

To actually deploy, use:

$ marathon-release deploy --domain-name dev --all-applications
INFO: loaded 1 applications defined in ./apps
INFO: deploying new application "/paas-monitor"
INFO: deployment running for application "/paas-monitor"

Downloading current application definitions

If you are interested to keep the current application definitions of the domain, type:

$ marathon-release download --domain-name dev

The resulting files will be written to ./deployments/dev/

Removing undefined applications

Sometimes you will find that applications are deployed that are no longer defined. To remove these, type:

$ marathon-release delete --domain-name dev  --dry-run
INFO: deleting application "/mies-monitor"
INFO: deleting application "/aap-monitor"

If you like what you see, run it without the --dry-run.

Generating new application definitions

If you are interested to see the application definitions for a domain that result from your configuration, type:

$ marathon-release generate --domain-name dev

The resulting files will be written to ./deployments/dev/