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Safe `host` update

Decidim is a multi-tenant system, and you can natively define the host of a tenant. decidim-rest_full will add some extra validation on the update of the host, to be sure the host is correctly binded before making the change. This will enable to expose safe endpoint to update the organizaiton through API without falling in a bad state.

General Infrastructure​

Infrastructure
The expected infrastructure used with this module include the following component:

  • A DNS service, like the ones provided by Gandi.net, infomaniak.com namecheap.org etc
  • A LoadBalancer (nginx, traefik, haproxy) that will redirect the host to the right decidim server adress
  • A decidim instance
  • An active-job runner, like sidekiq, good_queue or solid_queue

host validation​

When updating the host from the /system form, we will save the unconfirmed_host, and check periodically the DNS resolution of this unconfirmed host.
Once the unconfirmed host IP resolution match all your Loadbalancer ips (meaning: DNS are propagated and ready to user), then we do indeed the host updates.

These changes are represented through callout in the system administration:

  1. If there is no operation pending, display information
  2. If there is an operation pending, display again the information, but with a warning System administration panel to update host
    The general process is quiet simple, and needed little updates to the decidim code: Update host process

To make this work, we needed two thing:

  • Be able to save additional data to an organization.
  • Be able to know what are the IP of the loadbalancer.

Save additional data to an organization: extended_data​

We copy the logic from Decidim::User and applied it to Decidim::Organization, in order to save extra metadata (we need only unconfirmed_host here). This additional resource is created in a jointed table, and is exposed in the Rest API under the system scope.

The Extended Data unconfirmed_host behaves like this:

  1. If nil: we have nothing to update
  2. Else: we need to check if the DNS lookup of the unconfirmed host match the IPs of the loadbalancer.

related endpoints

Register IPs for the loadbalancer​

A configuration for the Decidim::Restfull module is available under Decidim::Restfull.config.loadbalancer_ips. This configuration variable is defined by default by an environnement variable DECIDIM_REST_LOADBALANCER_IPS. So you can configure loadbalancer ips using two technique:

  1. DECIDIM_REST_LOADBALANCER_IPS (recommended)
    CSV of IPv4 or IPV6 separated by comma. Example: 127.0.0.1, ::1.

  2. Initializer file

Decidim::Restfull.configure do |config|
  config.loadbalancer_ips = ["127.0.0.1", "::1"]
end