Class: MemCache::Server

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

Overview

This class represents a memcached server instance.

Constant Summary collapse

CONNECT_TIMEOUT =

The amount of time to wait to establish a connection with a memcached server. If a connection cannot be established within this time limit, the server will be marked as down.

0.25
SOCKET_TIMEOUT =

The amount of time to wait for a response from a memcached server. If a response isn’t received within this time limit, the server will be marked as down.

0.25
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 706

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?

  @memcache = memcache
  @host   = host
  @port   = port.to_i
  @weight = weight.to_i

  @multithread = @memcache.multithread
  @mutex = Mutex.new

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

Instance Attribute Details

#host ⇒ Object (readonly)

The host the memcached server is running on.



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# File 'lib/memcache.rb', line 680

def host
  @host
end

#port ⇒ Object (readonly)

The port the memcached server is listening on.



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# File 'lib/memcache.rb', line 685

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 695

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 700

def status
  @status
end

#weight ⇒ Object (readonly)

The weight given to the server.



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# File 'lib/memcache.rb', line 690

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 736

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 776

def close
  @mutex.lock if @multithread
  @sock.close if @sock && !@sock.closed?
  @sock   = nil
  @retry  = nil
  @status = "NOT CONNECTED"
ensure
  @mutex.unlock if @multithread
end

#inspect ⇒ Object

Return a string representation of the server object.



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# File 'lib/memcache.rb', line 726

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

#mark_dead(reason = "Unknown error") ⇒ Object

Mark the server as dead and close its socket.



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# File 'lib/memcache.rb', line 789

def mark_dead(reason = "Unknown error")
  @sock.close if @sock && !@sock.closed?
  @sock   = nil
  @retry  = Time.now + RETRY_DELAY

  @status = sprintf "%s:%s DEAD: %s, will retry at %s", @host, @port, reason, @retry
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 744

def socket
  @mutex.lock if @multithread
  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 = TCPTimeoutSocket.new @host, @port

    if Socket.constants.include? 'TCP_NODELAY' then
      @sock.setsockopt Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1
    end
    @retry  = nil
    @status = 'CONNECTED'
  rescue SocketError, SystemCallError, IOError, Timeout::Error => err
    mark_dead err.message
  end

  return @sock
ensure
  @mutex.unlock if @multithread
end