Class: GlobalUid::Base

Inherits:
Object
  • Object
show all
Defined in:
lib/global_uid/base.rb

Constant Summary collapse

GLOBAL_UID_DEFAULTS = 
{
  :connection_timeout   => 3,
  :connection_retry     => 10.minutes,
  :notifier             => Proc.new { |exception, message| ActiveRecord::Base.logger.error("GlobalUID error:  #{exception} #{message}") },
  :query_timeout        => 10,
  :increment_by         => 5,  # This will define the maximum number of servers that you can have
  :disabled             => false,
  :per_process_affinity => true,
  :dry_run              => false
}
GlobalUidTimer = 
Timeout

Class Method Summary collapse

Class Method Details

.create_uid_tables(id_table_name, options = {}) ⇒ Object 



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# File 'lib/global_uid/base.rb', line 35

def self.create_uid_tables(id_table_name, options={})
  type     = options[:uid_type] || "bigint(21) UNSIGNED"
  start_id = options[:start_id] || 1

  engine_stmt = "ENGINE=#{global_uid_options[:storage_engine] || "MyISAM"}"

  # TODO it would be nice to be able to set the engine or something to not be MySQL specific
  with_connections do |connection|
    connection.execute("CREATE TABLE IF NOT EXISTS `#{id_table_name}` (
    `id` #{type} NOT NULL AUTO_INCREMENT,
    `stub` char(1) NOT NULL DEFAULT '',
    PRIMARY KEY (`id`),
    UNIQUE KEY `stub` (`stub`)
    ) #{engine_stmt}")

    # prime the pump on each server
    connection.execute("INSERT IGNORE INTO `#{id_table_name}` VALUES(#{start_id}, 'a')")
  end
end

.disconnect! ⇒ Object 



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# File 'lib/global_uid/base.rb', line 116

def self.disconnect!
  self.servers = nil
end

.drop_uid_tables(id_table_name, options = {}) ⇒ Object 



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# File 'lib/global_uid/base.rb', line 55

def self.drop_uid_tables(id_table_name, options={})
  with_connections do |connection|
    connection.execute("DROP TABLE IF EXISTS `#{id_table_name}`")
  end
end

.get_connections(options = {}) ⇒ Object 



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# File 'lib/global_uid/base.rb', line 184

def self.get_connections(options = {})
  with_connections {}
end

.get_many_uids_for_class(klass, count, options = {}) ⇒ Object

Raises:



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# File 'lib/global_uid/base.rb', line 198

def self.get_many_uids_for_class(klass, count, options = {})
  return [] unless count > 0
  with_connections do |connection|
    GlobalUidTimer.timeout(self.global_uid_options[:query_timeout], TimeoutException) do
      increment_by = connection.select_value("SELECT @@auto_increment_increment")
      start_id = connection.insert("REPLACE INTO #{klass.global_uid_table} (stub) VALUES " + (["('a')"] * count).join(','))
      return start_id.step(start_id + (count-1) * increment_by, increment_by).to_a
    end
  end
  raise NoServersAvailableException, "All global UID servers are gone!"
end

.get_uid_for_class(klass, options = {}) ⇒ Object

Raises:



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# File 'lib/global_uid/base.rb', line 188

def self.get_uid_for_class(klass, options = {})
  with_connections do |connection|
    GlobalUidTimer.timeout(self.global_uid_options[:query_timeout], TimeoutException) do
      id = connection.insert("REPLACE INTO #{klass.global_uid_table} (stub) VALUES ('a')")
      return id
    end
  end
  raise NoServersAvailableException, "All global UID servers are gone!"
end

.global_uid_options ⇒ Object 



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# File 'lib/global_uid/base.rb', line 214

def self.global_uid_options
  @global_uid_options
end

.global_uid_options=(options) ⇒ Object 



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# File 'lib/global_uid/base.rb', line 210

def self.global_uid_options=(options)
  @global_uid_options = GLOBAL_UID_DEFAULTS.merge(options.symbolize_keys)
end

.global_uid_servers ⇒ Object 



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# File 'lib/global_uid/base.rb', line 218

def self.global_uid_servers
  self.global_uid_options[:id_servers]
end

.id_table_from_name(name) ⇒ Object 



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# File 'lib/global_uid/base.rb', line 222

def self.id_table_from_name(name)
  "#{name}_ids".to_sym
end

.init_server_info(options) ⇒ Object 



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# File 'lib/global_uid/base.rb', line 95

def self.init_server_info(options)
  id_servers = self.global_uid_servers

  raise "You haven't configured any id servers" if id_servers.nil? or id_servers.empty?
  raise "More servers configured than increment_by: #{id_servers.size} > #{options[:increment_by]} -- this will create duplicate IDs." if id_servers.size > options[:increment_by]

  offset = 1

  id_servers.map do |name, i|
    info = {}
    info[:cx]       = nil
    info[:name]     = name
    info[:retry_at] = nil
    info[:offset]   = offset
    info[:rand]     = rand
    info[:new?]     = true
    offset +=1
    info
  end
end

.new_connection(name, connection_timeout, offset, increment_by) ⇒ Object 



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# File 'lib/global_uid/base.rb', line 72

def self.new_connection(name, connection_timeout, offset, increment_by)
  raise "No id server '#{name}' configured in database.yml" unless ActiveRecord::Base.configurations.has_key?(name)
  config = ActiveRecord::Base.configurations[name]
  c = config.symbolize_keys

  raise "No global_uid support for adapter #{c[:adapter]}" if c[:adapter] != 'mysql2'

  con = nil
  begin
    GlobalUidTimer.timeout(connection_timeout, ConnectionTimeoutException) do
      con = ActiveRecord::Base.send("#{c[:adapter]}_connection", config)
    end
  rescue ConnectionTimeoutException => e
    notify e, "Timed out establishing a connection to #{name}"
    return nil
  rescue Exception => e
    notify e, "establishing a connection to #{name}: #{e.message}"
    return nil
  end

  con
end

.notify(exception, message) ⇒ Object 



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# File 'lib/global_uid/base.rb', line 178

def self.notify(exception, message)
  if self.global_uid_options[:notifier]
    self.global_uid_options[:notifier].call(exception, message)
  end
end

.servers ⇒ Object 



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# File 'lib/global_uid/base.rb', line 26

def self.servers
  # Thread local storage is inheritted on `fork`, include the pid
  Thread.current["global_uid_servers_#{$$}"]
end

.servers=(s) ⇒ Object 



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# File 'lib/global_uid/base.rb', line 31

def self.servers=(s)
  Thread.current["global_uid_servers_#{$$}"] = s
end

.setup_connections!(options) ⇒ Object 



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# File 'lib/global_uid/base.rb', line 120

def self.setup_connections!(options)
  connection_timeout = options[:connection_timeout]
  increment_by       = options[:increment_by]

  if self.servers.nil?
    self.servers = init_server_info(options)
    # sorting here sets up each process to have affinity to a particular server.
    self.servers = self.servers.sort_by { |s| s[:rand] }
  end

  self.servers.each do |info|
    next if info[:cx]

    if info[:new?] || ( info[:retry_at] && Time.now > info[:retry_at] )
      info[:new?] = false

      connection = new_connection(info[:name], connection_timeout, info[:offset], increment_by)
      info[:cx]  = connection
      info[:retry_at] = Time.now + options[:connection_retry] if connection.nil?
    end
  end

  self.servers
end

.with_connections(options = {}) ⇒ Object

Raises:



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# File 'lib/global_uid/base.rb', line 145

def self.with_connections(options = {})
  options = self.global_uid_options.merge(options)
  servers = setup_connections!(options)

  if !options[:per_process_affinity]
    servers = servers.sort_by { rand } #yes, I know it's not true random.
  end

  raise NoServersAvailableException if servers.empty?

  errors = []
  servers.each do |s|
    begin
      yield s[:cx] if s[:cx]
    rescue TimeoutException, Exception => e
      notify e, "#{e.message}"
      errors << e
      s[:cx] = nil
      s[:retry_at] = Time.now + 1.minute
    end
  end

  # in the case where all servers are gone, put everyone back in.
  if servers.all? { |info| info[:cx].nil? }
    servers.each do |info|
      info[:retry_at] = Time.now - 5.minutes
    end
    raise NoServersAvailableException, "Errors hit: #{errors.map(&:to_s).join(',')}"
  end

  servers.map { |s| s[:cx] }.compact
end