GraphQL Connections With ActiveRecord Connection Switching

ar-connections-test.rb

require "bundler/inline"

gemfile do
  gem "graphql", "1.12.20"
  gem "graphql-pro", "1.20.2"
  gem "rails"
  gem "sqlite3"
end

require "active_record"

ActiveRecord::Base.legacy_connection_handling = false
ActiveRecord::Base.configurations = {
  primary: { adapter: "sqlite3", database: "ar_test.db" },
  replica: { adapter: "sqlite3", database: "ar_test.db", replica: true },
}
ActiveRecord::Base.establish_connection(:primary)

ActiveRecord::Schema.define do
  self.verbose = false
  create_table :things, force: true do |t|
    t.column :name, :string
  end
end


class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true
  connects_to database: { writing: :primary, reading: :replica }
end


class Thing < ApplicationRecord
end

Thing.create!(name: "Hat")
Thing.create!(name: "Lamp")
Thing.create!(name: "Tree")

class SqliteReadConnection < GraphQL::Pro::SqliteStableRelationConnection
  def load_nodes
    puts "Connecting to Reading"
    ActiveRecord::Base.connected_to(role: :reading) { super }
  ensure
    puts "Disconnecting from Reading"
  end
end

class Schema < GraphQL::Schema
  class Thing < GraphQL::Schema::Object
    field :name, String, null: false
  end

  class Query < GraphQL::Schema::Object
    field :things, Thing.connection_type, null: false

    def things
      SqliteReadConnection.new(::Thing.all)
    end
  end

  query(Query)

  connections.add(ActiveRecord::Relation, GraphQL::Pro::SqliteStableRelationConnection)
end

ActiveRecord::Base.logger = Logger.new(STDOUT)

pp Schema.execute("{ things(first: 5) { nodes { name } } }").to_h

# After: it runs just one database query for the GraphQL query:
#
# ~/code/graphql-ruby $ ruby ar-connections-test.rb
# Connecting to Reading
# D, [2021-11-23T09:19:50.011583 #56567] DEBUG -- :    (0.0ms)  SELECT sqlite_version(*)
# D, [2021-11-23T09:19:50.011926 #56567] DEBUG -- :   Thing Load (0.1ms)  SELECT things.*, things.id AS cursor_0 FROM "things" ORDER BY things.id asc LIMIT ?  [["LIMIT", 6]]
# Disconnecting from Reading
# {"data"=>
#   {"things"=>{"nodes"=>[{"name"=>"Hat"}, {"name"=>"Lamp"}, {"name"=>"Tree"}]}}}