An experimental Sidekiq middleware that validates the Sequel connection before each run.

sidekiq_sequel_validate_connection_middleware.rb

module SidekiqSequel
  module Middleware
    class Server
      attr_reader :db

      def initialize(options = nil)
        @db = options[:db]
        @max_retry = options.fetch(:max_retry, 5)
        @error_classes = @db.send(:database_error_classes).dup.freeze
      end

      def call(_worker, _job, _queue)
        validate_connection
        yield
      end

      def validate_connection
        # This forces the use of `acquire` which will raises a
        # DatabaseDisconnectError, but also cleaning this connection from
        # the connection pool correctly
        db.run(test_connection_sql)
      rescue ::Sequel::DatabaseDisconnectError, *@error_classes
        if (@max_retry -= 1) >= 0
          retry
        else
          raise $!
        end
      end

      def test_connection_sql
        @test_connection_sql ||= db.select(nil).sql
      end
    end
  end
end