Class: Sequel::ConnectionPool

Class | Sequel::ConnectionPool
In: | lib/sequel_core/connection_pool.rb
Parent: | Object

A ConnectionPool manages access to database connections by keeping multiple connections and giving threads exclusive access to each connection.

### Methods

allocated available_connections created_count disconnect hold new size

### Attributes

connection_proc | [RW] | The proc used to create a new database connection.
disconnection_proc | [RW] | The proc used to disconnect a database connection.
max_size | [R] | The maximum number of connections.
mutex | [R] | The mutex that protects access to the other internal vairables. You must use this if you want to manipulate the variables safely.

### Public Class methods

new(opts = {}, &block)

Constructs a new pool with a maximum size. If a block is supplied, it is used to create new connections as they are needed.

      pool = ConnectionPool.new(:max_connections=>10) {MyConnection.new(opts)}

The connection creation proc can be changed at any time by assigning a Proc to pool#connection_proc.

      pool = ConnectionPool.new(:max_connections=>10)
      pool.connection_proc = proc {MyConnection.new(opts)}

The connection pool takes the following options:

- :max_connections - The maximum number of connections the connection pool will open (default 4)
- :pool_convert_exceptions - Whether to convert non-StandardError based exceptions to RuntimeError exceptions (default true)
- :pool_sleep_time - The amount of time to sleep before attempting to acquire a connection again (default 0.001)
- :pool_timeout - The amount of seconds to wait to acquire a connection before raising a PoolTimeoutError (default 5)
- :servers - A hash of servers to use. Keys should be symbols. If not present, will use a single :default server. The server name symbol will be passed to the connection_proc.

[Source]

        # File lib/sequel_core/connection_pool.rb, line 42
    42:   def initialize(opts = {}, &block)
    43:     @max_size = opts[:max_connections] || 4
    44:     @mutex = Mutex.new
    45:     @connection_proc = block
    46:     @disconnection_proc = opts[:disconnection_proc]
    47:     @servers = [:default]
    48:     @servers += opts[:servers].keys - @servers if opts[:servers]
    49:     @available_connections = Hash.new{|h,k| h[:default]}
    50:     @allocated = Hash.new{|h,k| h[:default]}
    51:     @created_count = Hash.new{|h,k| h[:default]}
    52:     @servers.each do |s|
    53:       @available_connections[s] = []
    54:       @allocated[s] = {}
    55:       @created_count[s] = 0
    56:     end
    57:     @timeout = opts[:pool_timeout] || 5
    58:     @sleep_time = opts[:pool_sleep_time] || 0.001
    59:     @convert_exceptions = opts.include?(:pool_convert_exceptions) ? opts[:pool_convert_exceptions] : true
    60:   end

### Public Instance methods

allocated(server=:default)

A hash of connections currently being used for the given server, key is the Thread, value is the connection.

[Source]

        # File lib/sequel_core/connection_pool.rb, line 64
    64:   def allocated(server=:default)
    65:     @allocated[server]
    66:   end

available_connections(server=:default)

An array of connections opened but not currently used, for the given server.

[Source]

        # File lib/sequel_core/connection_pool.rb, line 70
    70:   def available_connections(server=:default)
    71:     @available_connections[server]
    72:   end

created_count(server=:default)

The total number of connections opened for the given server, should be equal to available_connections.length + allocated.length

[Source]

        # File lib/sequel_core/connection_pool.rb, line 76
    76:   def created_count(server=:default)
    77:     @created_count[server]
    78:   end

disconnect(&block)

Removes all connection currently available on all servers, optionally yielding each connection to the given block. This method has the effect of disconnecting from the database, assuming that no connections are currently being used. Once a connection is requested using hold, the connection pool creates new connections to the database.

[Source]

         # File lib/sequel_core/connection_pool.rb, line 126
    126:   def disconnect(&block)
    127:     block ||= @disconnection_proc
    128:     @mutex.synchronize do
    129:       @available_connections.each do |server, conns|
    130:         conns.each{|c| block.call(c)} if block
    131:         conns.clear
    132:         set_created_count(server, allocated(server).length)
    133:       end
    134:     end
    135:   end

hold(server=:default) {|conn| ...}

Chooses the first available connection to the given server, or if none are available, creates a new connection. Passes the connection to the supplied block:

      pool.hold {|conn| conn.execute('DROP TABLE posts')}

Pool#hold is re-entrant, meaning it can be called recursively in the same thread without blocking.

If no connection is immediately available and the pool is already using the maximum number of connections, Pool#hold will block until a connection is available or the timeout expires. If the timeout expires before a connection can be acquired, a Sequel::Error::PoolTimeoutError is raised.

[Source]

         # File lib/sequel_core/connection_pool.rb, line 95
     95:   def hold(server=:default)
     96:     begin
     97:       t = Thread.current
     98:       time = Time.new
     99:       timeout = time + @timeout
    100:       sleep_time = @sleep_time
    101:       if conn = owned_connection(t, server)
    102:         return yield(conn)
    103:       end
    104:       until conn = acquire(t, server)
    105:         raise(::Sequel::Error::PoolTimeoutError) if Time.new > timeout
    106:         sleep sleep_time
    107:       end
    108:       begin
    109:         yield conn
    110:       rescue Sequel::DatabaseDisconnectError => dde
    111:         remove(t, conn, server)
    112:         raise
    113:       ensure
    114:         release(t, conn, server) unless dde
    115:       end
    116:     rescue Exception => e
    117:       raise(@convert_exceptions && !e.is_a?(StandardError) ? RuntimeError.new(e.message) : e)
    118:     end
    119:   end

size(server=:default)

Alias for created_count

[Validate]