A simple libcluster strategy for Google Instance Groups

Installation

If available in Hex, the package can be installed by adding libcluster_gig to your list of dependencies in mix.exs:

def deps do
  [
    {:libcluster_gig, "~> 0.3.0"}
  ]
end

Setup

This library is using the Google APIs to call various services, and you'll need to provide an access token. Excerpt from Google's API docs, in relation to obtaining an Access Token

Service Accounts

Authentication is typically done through Application Default Credentials which means you do not have to change the code to authenticate as long as your environment has credentials. Start by creating a Service Account key file. This file can be used to authenticate to Google Cloud Platform services from any environment. To use the file, set the GOOGLE_APPLICATION_CREDENTIALS environment variable to the path to the key file, for example:

export GOOGLE_APPLICATION_CREDENTIALS=/path/to/service_account.json

If you are deploying to App Engine, Compute Engine, or Container Engine, your credentials will be available by default.

Usage

In your application supervision tree, add this custom libcluster strategy.

defmodule MyApp.Application do
  use Application

  def start(_type, _args) do
    topologies = [
      myapp_release_name: [
        strategy: Cluster.Strategy.GoogleInstanceGroups,
        config: [
          project: "4thehorde",
          zone: "kekw",
          instance_group: "omegalul",
          adapter: Cluster.Strategy.Adapter.InstanceGroups
        ]
      ]
    ]

    children = [
      {Cluster.Supervisor, [topologies, [name: GoogleInstanceGroups.ClusterSupervisor]]}
    ]

    Supervisor.start_link(children, [name: MyApp.Supervisor, strategy: :one_for_one])
  end
end

But you can also use a libcluster specific configuration. For example:

config :libcluster,
  topologies: [
    myapp_release_name: [
      strategy: Cluster.Strategy.GoogleInstanceGroups,
      config: [
        project: "4thehorde",
        zone: "kekw",
        instance_group: "omegalul",
        adapter: Cluster.Strategy.Adapter.InstanceGroups
      ]
    ]
  ]

and then add the following to one of your app's supervision trees, as a child

  {Cluster.Supervisor,
    [Application.get_env(:libcluster, :topologies), [name: MyApp.ClusterSupervisor]]}

That's it™

:)

License

Copyright 2020-2021 Florin T.Patrascu

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.