Backend-switching based blue-green deployements.

This role will let you swap haproxy backends depending on the deployed color.

When used, it will create two backends: blue and green. You call this role with blue_green_color set to blue or green, and it will set the current color to blue_green_color.

It works by setting the inactive color backend to disabled.

The blue-green deployement process roughly follows this pattern:

• check which color is the oldest (and thus, can be deployed)
• deploy application to the corresponding color target (a directory for instance)
• point loadbalancers to the new color

Any pre-requisites that may not be covered by the ansible itself or the role should be mentioned here. For instance, if the role uses the EC2 module, it may be a good idea to mention in this section that the boto package is required.

• haproxy_blue_green_front_name: HAproxy frontend entry name to create
• haproxy_blue_green_loadbalancers: Group name of loadbalancers to configure
• haproxy_blue_green_backend_group: Group name of backend to add in the backend

The role is supposed to be used this way from a playbook:

- { role: leucos.haproxy-blue-green,
    haproxy_blue_green_front_name: 'myfront',
    haproxy_blue_green_loadbalancers: 'lb',
    haproxy_blue_green_backend_group: 'www',
    when: blue_green_color is defined }

blue_green_color can be set earlier in the playbook using leucos.blue-green role, which tries to guess which color is the oldest (and thus, can be redeployed).

This role depends on:

• leucos.haproxy-multi for HAProxy configuration (using multiple configuration file)
• leucos.blue-green for blue-green color guessing

MIT

@leucos