Class: Dalli::Client

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

Instance Method Summary collapse

Constructor Details

#initialize(servers = nil, options = {}) ⇒ Client

Dalli::Client is the main class which developers will use to interact with the memcached server. Usage:

Dalli::Client.new(['localhost:11211:10', 'cache-2.example.com:11211:5', '192.168.0.1:22122:5'],
                :threadsafe => true, :failover => true, :expires_in => 300)

servers is an Array of “host:port:weight” where weight allows you to distribute cache unevenly. Both weight and port are optional. If you pass in nil, Dalli will use the MEMCACHE_SERVERS environment variable or default to 'localhost:11211' if it is not present.

Options:

  • :namespace - prepend each key with this value to provide simple namespacing.

  • :failover - if a server is down, look for and store values on another server in the ring. Default: true.

  • :threadsafe - ensure that only one thread is actively using a socket at a time. Default: true.

  • :expires_in - default TTL in seconds if you do not pass TTL as a parameter to an individual operation, defaults to 0 or forever

  • :compress - defaults to false, if true Dalli will compress values larger than 1024 bytes before sending them to memcached.

  • :serializer - defaults to Marshal

  • :compressor - defaults to zlib


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# File 'lib/dalli/client.rb', line 28

def initialize(servers=nil, options={})
  @servers = normalize_servers(servers || ENV["MEMCACHE_SERVERS"] || '127.0.0.1:11211')
  @options = normalize_options(options)
  @ring = nil
end

Instance Method Details

#add(key, value, ttl = nil, options = nil) ⇒ Object

Conditionally add a key/value pair, if the key does not already exist on the server. Returns true if the operation succeeded.


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# File 'lib/dalli/client.rb', line 205

def add(key, value, ttl=nil, options=nil)
  ttl ||= @options[:expires_in].to_i
  perform(:add, key, value, ttl, options)
end

#append(key, value) ⇒ Object

Append value to the value already stored on the server for 'key'. Appending only works for values stored with :raw => true.


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# File 'lib/dalli/client.rb', line 225

def append(key, value)
  perform(:append, key, value.to_s)
end

#cas(key, ttl = nil, options = nil, &block) ⇒ Object

compare and swap values using optimistic locking. Fetch the existing value for key. If it exists, yield the value to the block. Add the block's return value as the new value for the key. Add will fail if someone else changed the value.

Returns:

  • nil if the key did not exist.

  • false if the value was changed by someone else.

  • true if the value was successfully updated.


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# File 'lib/dalli/client.rb', line 187

def cas(key, ttl=nil, options=nil, &block)
  ttl ||= @options[:expires_in].to_i
  (value, cas) = perform(:cas, key)
  value = (!value || value == 'Not found') ? nil : value
  if value
    newvalue = block.call(value)
    perform(:set, key, newvalue, ttl, cas, options)
  end
end

#closeObject Also known as: reset

Close our connection to each server. If you perform another operation after this, the connections will be re-established.


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# File 'lib/dalli/client.rb', line 314

def close
  if @ring
    @ring.servers.each { |s| s.close }
    @ring = nil
  end
end

#decr(key, amt = 1, ttl = nil, default = nil) ⇒ Object

Decr subtracts the given amount from the counter on the memcached server. Amt must be a positive integer value.

memcached counters are unsigned and cannot hold negative values. Calling decr on a counter which is 0 will just return 0.

If default is nil, the counter must already exist or the operation will fail and will return nil. Otherwise this method will return the new value for the counter.

Note that the ttl will only apply if the counter does not already exist. To decrease an existing counter and update its TTL, use #cas.

Raises:

  • (ArgumentError)

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# File 'lib/dalli/client.rb', line 274

def decr(key, amt=1, ttl=nil, default=nil)
  raise ArgumentError, "Positive values only: #{amt}" if amt < 0
  ttl ||= @options[:expires_in].to_i
  perform(:decr, key, amt.to_i, ttl, default)
end

#delete(key) ⇒ Object


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# File 'lib/dalli/client.rb', line 218

def delete(key)
  perform(:delete, key)
end

#fetch(key, ttl = nil, options = nil) ⇒ Object


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# File 'lib/dalli/client.rb', line 166

def fetch(key, ttl=nil, options=nil)
  ttl ||= @options[:expires_in].to_i
  val = get(key, options)
  if val.nil? && block_given?
    val = yield
    add(key, val, ttl, options)
  end
  val
end

#flush(delay = 0) ⇒ Object Also known as: flush_all


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# File 'lib/dalli/client.rb', line 236

def flush(delay=0)
  time = -delay
  ring.servers.map { |s| s.request(:flush, time += delay) }
end

#get(key, options = nil) ⇒ Object


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# File 'lib/dalli/client.rb', line 61

def get(key, options=nil)
  resp = perform(:get, key)
  resp.nil? || 'Not found' == resp ? nil : resp
end

#get_multi(*keys) ⇒ Object

Fetch multiple keys efficiently. Returns a hash of { 'key' => 'value', 'key2' => 'value1' }


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# File 'lib/dalli/client.rb', line 69

def get_multi(*keys)
  perform do
    return {} if keys.empty?
    options = nil
    options = keys.pop if keys.last.is_a?(Hash) || keys.last.nil?
    ring.lock do
      begin
        mapped_keys = keys.flatten.map {|a| validate_key(a.to_s)}
        groups = mapped_keys.flatten.group_by do |key|
          begin
            ring.server_for_key(key)
          rescue Dalli::RingError
            Dalli.logger.debug { "unable to get key #{key}" }
            nil
          end
        end
        if unfound_keys = groups.delete(nil)
          Dalli.logger.debug { "unable to get keys for #{unfound_keys.length} keys because no matching server was found" }
        end

        groups.each do |server, keys_for_server|
          begin
            # TODO: do this with the perform chokepoint?
            # But given the fact that fetching the response doesn't take place
            # in that slot it's misleading anyway. Need to move all of this method
            # into perform to be meaningful
            server.request(:send_multiget, keys_for_server)
          rescue DalliError, NetworkError => e
            Dalli.logger.debug { e.inspect }
            Dalli.logger.debug { "unable to get keys for server #{server.hostname}:#{server.port}" }
          end
        end

        servers = groups.keys
        values = {}
        return values if servers.empty?

        servers.each do |server|
          next unless server.alive?
          begin
            server.multi_response_start
          rescue DalliError, NetworkError => e
            Dalli.logger.debug { e.inspect }
            Dalli.logger.debug { "results from this server will be missing" }
            servers.delete(server)
          end
        end

        start = Time.now
        loop do
          # remove any dead servers
          servers.delete_if { |s| s.sock.nil? }
          break if servers.empty?

          # calculate remaining timeout
          elapsed = Time.now - start
          timeout = servers.first.options[:socket_timeout]
          if elapsed > timeout
            readable = nil
          else
            sockets = servers.map(&:sock)
            readable, _ = IO.select(sockets, nil, nil, timeout - elapsed)
          end

          if readable.nil?
            # no response within timeout; abort pending connections
            servers.each do |server|
              Dalli.logger.debug { "memcached at #{server.name} did not response within timeout" }
              server.multi_response_abort
            end
            break

          else
            readable.each do |sock|
              server = sock.server

              begin
                server.multi_response_nonblock.each do |key, value|
                  values[key_without_namespace(key)] = value
                end

                if server.multi_response_completed?
                  servers.delete(server)
                end
              rescue NetworkError
                servers.delete(server)
              end
            end
          end
        end

        values
      end
    end
  end
end

#incr(key, amt = 1, ttl = nil, default = nil) ⇒ Object

Incr adds the given amount to the counter on the memcached server. Amt must be a positive integer value.

If default is nil, the counter must already exist or the operation will fail and will return nil. Otherwise this method will return the new value for the counter.

Note that the ttl will only apply if the counter does not already exist. To increase an existing counter and update its TTL, use #cas.

Raises:

  • (ArgumentError)

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# File 'lib/dalli/client.rb', line 254

def incr(key, amt=1, ttl=nil, default=nil)
  raise ArgumentError, "Positive values only: #{amt}" if amt < 0
  ttl ||= @options[:expires_in].to_i
  perform(:incr, key, amt.to_i, ttl, default)
end

#multiObject

Turn on quiet aka noreply support. All relevant operations within this block will be effectively pipelined as Dalli will use 'quiet' operations where possible. Currently supports the set, add, replace and delete operations.


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# File 'lib/dalli/client.rb', line 54

def multi
  old, Thread.current[:dalli_multi] = Thread.current[:dalli_multi], true
  yield
ensure
  Thread.current[:dalli_multi] = old
end

#normalize_servers(servers) ⇒ Object

Normalizes the argument into an array of servers. If the argument is a string, it's expected to be of the format “memcache1.example.com:11211[,memcache2.example.com:11211[,memcache3.example.com:11211]]


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# File 'lib/dalli/client.rb', line 37

def normalize_servers(servers)
  if servers.is_a? String
    return servers.split(",")
  else
    return servers
  end
end

#prepend(key, value) ⇒ Object

Prepend value to the value already stored on the server for 'key'. Prepending only works for values stored with :raw => true.


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# File 'lib/dalli/client.rb', line 232

def prepend(key, value)
  perform(:prepend, key, value.to_s)
end

#replace(key, value, ttl = nil, options = nil) ⇒ Object

Conditionally add a key/value pair, only if the key already exists on the server. Returns true if the operation succeeded.


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# File 'lib/dalli/client.rb', line 213

def replace(key, value, ttl=nil, options=nil)
  ttl ||= @options[:expires_in].to_i
  perform(:replace, key, value, ttl, options)
end

#reset_statsObject

Reset stats for each server.


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# File 'lib/dalli/client.rb', line 305

def reset_stats
  ring.servers.map do |server|
    server.alive? ? server.request(:reset_stats) : nil
  end
end

#set(key, value, ttl = nil, options = nil) ⇒ Object


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# File 'lib/dalli/client.rb', line 197

def set(key, value, ttl=nil, options=nil)
  ttl ||= @options[:expires_in].to_i
  perform(:set, key, value, ttl, 0, options)
end

#stats(type = nil) ⇒ Object

Collect the stats for each server. You can optionally pass a type including :items or :slabs to get specific stats Returns a hash like { 'hostname:port' => { 'stat1' => 'value1', … }, 'hostname2:port' => { … } }


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# File 'lib/dalli/client.rb', line 294

def stats(type=nil)
  type = nil if ![nil, :items,:slabs].include? type
  values = {}
  ring.servers.each do |server|
    values["#{server.hostname}:#{server.port}"] = server.alive? ? server.request(:stats,type.to_s) : nil
  end
  values
end

#touch(key, ttl = nil) ⇒ Object

Touch updates expiration time for a given key.

Returns true if key exists, otherwise nil.


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# File 'lib/dalli/client.rb', line 284

def touch(key, ttl=nil)
  ttl ||= @options[:expires_in].to_i
  resp = perform(:touch, key, ttl)
  resp.nil? ? nil : true
end