Contents

require "makara"
require "distribute_reads/appropriate_pool"
require "distribute_reads/cache_store"
require "distribute_reads/global_methods"
require "distribute_reads/version"

module DistributeReads
  class Error < StandardError; end
  class TooMuchLag < Error; end
  class NoReplicasAvailable < Error; end

  class << self
    attr_accessor :by_default
    attr_accessor :default_options
  end
  self.by_default = false
  self.default_options = {
    failover: true,
    lag_failover: false
  }

  def self.lag(connection: nil)
    raise DistributeReads::Error, "Don't use outside distribute_reads" unless Thread.current[:distribute_reads]

    connection ||= ActiveRecord::Base.connection
    if %w(PostgreSQL PostGIS).include?(connection.adapter_name)
      replica_pool = connection.instance_variable_get(:@slave_pool)
      if replica_pool && replica_pool.connections.size > 1
        warn "[distribute_reads] Multiple replicas available, lag only reported for one"
      end

      connection.execute(
        "SELECT CASE
          WHEN NOT pg_is_in_recovery() OR pg_last_xlog_receive_location() = pg_last_xlog_replay_location() THEN 0
          ELSE EXTRACT (EPOCH FROM NOW() - pg_last_xact_replay_timestamp())
        END AS lag"
      ).first["lag"].to_f
    else
      raise DistributeReads::Error, "Option not supported with this adapter"
    end
  end

  # legacy
  def self.default_to_primary
    !by_default
  end

  # legacy
  def self.default_to_primary=(value)
    self.by_default = !value
  end
end

Makara::Proxy.send :prepend, DistributeReads::AppropriatePool
Object.send :include, DistributeReads::GlobalMethods

ActiveSupport.on_load(:active_job) do
  require "distribute_reads/job_methods"
  include DistributeReads::JobMethods
end

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
distribute_reads-0.2.0	lib/distribute_reads.rb