redict/client-libraries/ruby/lib/server.rb

begin
  # Timeout code is courtesy of Ruby memcache-client
  #   http://github.com/mperham/memcache-client/tree
  # Try to use the SystemTimer gem instead of Ruby's timeout library
  # when running on something that looks like Ruby 1.8.x.  See:
  #   http://ph7spot.com/articles/system_timer
  # We don't want to bother trying to load SystemTimer on jruby and
  # ruby 1.9+.
  if defined?(JRUBY_VERSION) || (RUBY_VERSION >= '1.9')
    require 'timeout'
    RedisTimer = Timeout
  else
    require 'system_timer'
    RedisTimer = SystemTimer
  end
rescue LoadError => e
  puts "[redis-rb] Could not load SystemTimer gem, falling back to Ruby's slower/unsafe timeout library: #{e.message}"
  require 'timeout'
  RedisTimer = Timeout
end

##
# This class represents a redis server instance.

class Server

  ##
  # The amount of time to wait before attempting to re-establish a
  # connection with a server that is marked dead.

  RETRY_DELAY = 30.0

  ##
  # The host the redis server is running on.

  attr_reader :host

  ##
  # The port the redis server is listening on.

  attr_reader :port
  
  ##
  #
  
  attr_reader :replica

  ##
  # The time of next retry if the connection is dead.

  attr_reader :retry

  ##
  # A text status string describing the state of the server.

  attr_reader :status

  ##
  # Create a new Redis::Server object for the redis instance
  # listening on the given host and port.

  def initialize(host, port = DEFAULT_PORT, timeout = 10)
    raise ArgumentError, "No host specified" if host.nil? or host.empty?
    raise ArgumentError, "No port specified" if port.nil? or port.to_i.zero?

    @host   = host
    @port   = port.to_i

    @sock   = nil
    @retry  = nil
    @status = 'NOT CONNECTED'
    @timeout = timeout
  end

  ##
  # Return a string representation of the server object.
  def inspect
    "<Redis::Server: %s:%d (%s)>" % [@host, @port, @status]
  end

  ##
  # Try to connect to the redis server targeted by this object.
  # Returns the connected socket object on success or nil on failure.

  def socket
    return @sock if @sock and not @sock.closed?

    @sock = nil

    # If the host was dead, don't retry for a while.
    return if @retry and @retry > Time.now

    # Attempt to connect if not already connected.
    begin
      @sock = connect_to(@host, @port, @timeout)
      @sock.setsockopt Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1
      @retry  = nil
      @status = 'CONNECTED'
    rescue Errno::EPIPE, Errno::ECONNREFUSED => e
      puts "Socket died... socket: #{@sock.inspect}\n" if $debug
      @sock.close
      retry
    rescue SocketError, SystemCallError, IOError => err
      puts "Unable to open socket: #{err.class.name}, #{err.message}" if $debug
      mark_dead err
    end
    @sock
  end

  def connect_to(host, port, timeout=nil)
    socket = TCPSocket.new(host, port, 0)
    if timeout
      socket.instance_eval <<-EOR
        alias :blocking_gets :gets
        def gets(*args)
          RedisTimer.timeout(#{timeout}) do
            self.blocking_gets(*args)
          end
        end
        alias :blocking_read :read
        def read(*args)
          RedisTimer.timeout(#{timeout}) do
            self.blocking_read(*args)
          end
        end
        alias :blocking_write :write
        def write(*args)
          RedisTimer.timeout(#{timeout}) do
            self.blocking_write(*args)
          end
        end
      EOR
    end
    socket
  end

  ##
  # Close the connection to the redis server targeted by this
  # object.  The server is not considered dead.

  def close
    @sock.close if @sock && !@sock.closed?
    @sock   = nil
    @retry  = nil
    @status = "NOT CONNECTED"
  end

  ##
  # Mark the server as dead and close its socket.
  def mark_dead(error)
    @sock.close if @sock && !@sock.closed?
    @sock   = nil
    @retry  = Time.now #+ RETRY_DELAY

    reason = "#{error.class.name}: #{error.message}"
    @status = sprintf "%s:%s DEAD (%s), will retry at %s", @host, @port, reason, @retry
    puts @status
  end

end