Class: MemCache::Server

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

Overview

This class represents a memcached server instance.

Constant Summary collapse

RETRY_DELAY =

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

30.0

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(memcache, host, port = DEFAULT_PORT, weight = DEFAULT_WEIGHT) ⇒ Server

Create a new MemCache::Server object for the memcached instance listening on the given host and port, weighted by the given weight.

Raises:

  • (ArgumentError) 


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# File 'lib/memcache.rb', line 964

def initialize(memcache, host, port = DEFAULT_PORT, weight = DEFAULT_WEIGHT)
  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
  @weight = weight.to_i

  @sock   = nil
  @retry  = nil
  @status = 'NOT CONNECTED'
  @timeout = memcache.timeout
  @logger = memcache.logger
end

Instance Attribute Details

#host ⇒ Object (readonly)

The host the memcached server is running on.



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# File 'lib/memcache.rb', line 936

def host
  @host
end

#logger ⇒ Object (readonly)

Returns the value of attribute logger.



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# File 'lib/memcache.rb', line 958

def logger
  @logger
end

#port ⇒ Object (readonly)

The port the memcached server is listening on.



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# File 'lib/memcache.rb', line 941

def port
  @port
end

#retry ⇒ Object (readonly)

The time of next retry if the connection is dead.



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# File 'lib/memcache.rb', line 951

def retry
  @retry
end

#status ⇒ Object (readonly)

A text status string describing the state of the server.



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# File 'lib/memcache.rb', line 956

def status
  @status
end

#weight ⇒ Object (readonly)

The weight given to the server.



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# File 'lib/memcache.rb', line 946

def weight
  @weight
end

Instance Method Details

#alive? ⇒ Boolean

Check whether the server connection is alive. This will cause the socket to attempt to connect if it isn’t already connected and or if the server was previously marked as down and the retry time has been exceeded.

Returns:

  • (Boolean) 


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# File 'lib/memcache.rb', line 992

def alive?
  !!socket
end

#close ⇒ Object

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



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# File 'lib/memcache.rb', line 1053

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

#connect_to(host, port, timeout = nil) ⇒ Object 



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# File 'lib/memcache.rb', line 1022

def connect_to(host, port, timeout=nil)
  addr = Socket.getaddrinfo(host, nil)
  sock = Socket.new(Socket.const_get(addr[0][0]), Socket::SOCK_STREAM, 0)

  if timeout
    secs = Integer(timeout)
    usecs = Integer((timeout - secs) * 1_000_000)
    optval = [secs, usecs].pack("l_2")
    sock.setsockopt Socket::SOL_SOCKET, Socket::SO_RCVTIMEO, optval
    sock.setsockopt Socket::SOL_SOCKET, Socket::SO_SNDTIMEO, optval

    # Socket timeouts don't work for more complex IO operations
    # like gets which lay on top of read.  We need to fall back to
    # the standard Timeout mechanism.
    sock.instance_eval <<-EOR
      alias :blocking_gets :gets
      def gets
        MemCacheTimer.timeout(#{timeout}) do
          self.blocking_gets
        end
      end
    EOR
  end
  sock.connect(Socket.pack_sockaddr_in(port, addr[0][3]))
  sock
end

#inspect ⇒ Object

Return a string representation of the server object.



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# File 'lib/memcache.rb', line 982

def inspect
  "<MemCache::Server: %s:%d [%d] (%s)>" % [@host, @port, @weight, @status]
end

#mark_dead(error) ⇒ Object

Mark the server as dead and close its socket.



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# File 'lib/memcache.rb', line 1063

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
  @logger.info { @status } if @logger
end

#socket ⇒ Object

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



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# File 'lib/memcache.rb', line 1000

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 SocketError, SystemCallError, IOError => err
    logger.warn { "Unable to open socket: #{err.class.name}, #{err.message}" } if logger
    mark_dead err
  end

  return @sock
end