Class | Sequel::ConnectionPool |
In: |
lib/sequel/connection_pool.rb
|
Parent: | Object |
A ConnectionPool manages access to database connections by keeping multiple connections and giving threads exclusive access to each connection.
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. |
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:
# File lib/sequel/connection_pool.rb, line 43 43: def initialize(opts = {}, &block) 44: @max_size = opts[:max_connections] || 4 45: @mutex = Mutex.new 46: @connection_proc = block 47: @disconnection_proc = opts[:disconnection_proc] 48: @servers = [:default] 49: @servers += opts[:servers].keys - @servers if opts[:servers] 50: @available_connections = Hash.new{|h,k| h[:default]} 51: @allocated = Hash.new{|h,k| h[:default]} 52: @created_count = Hash.new{|h,k| h[:default]} 53: @servers.each do |s| 54: @available_connections[s] = [] 55: @allocated[s] = {} 56: @created_count[s] = 0 57: end 58: @timeout = opts[:pool_timeout] || 5 59: @sleep_time = opts[:pool_sleep_time] || 0.001 60: @convert_exceptions = opts.include?(:pool_convert_exceptions) ? opts[:pool_convert_exceptions] : true 61: end
A hash of connections currently being used for the given server, key is the Thread, value is the connection.
# File lib/sequel/connection_pool.rb, line 65 65: def allocated(server=:default) 66: @allocated[server] 67: end
An array of connections opened but not currently used, for the given server.
# File lib/sequel/connection_pool.rb, line 71 71: def available_connections(server=:default) 72: @available_connections[server] 73: end
The total number of connections opened for the given server, should be equal to available_connections.length + allocated.length
# File lib/sequel/connection_pool.rb, line 77 77: def created_count(server=:default) 78: @created_count[server] 79: end
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.
# File lib/sequel/connection_pool.rb, line 127 127: def disconnect(&block) 128: block ||= @disconnection_proc 129: @mutex.synchronize do 130: @available_connections.each do |server, conns| 131: conns.each{|c| block.call(c)} if block 132: conns.clear 133: set_created_count(server, allocated(server).length) 134: end 135: end 136: end
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::PoolTimeout is raised.
# File lib/sequel/connection_pool.rb, line 96 96: def hold(server=:default) 97: begin 98: t = Thread.current 99: time = Time.new 100: timeout = time + @timeout 101: sleep_time = @sleep_time 102: if conn = owned_connection(t, server) 103: return yield(conn) 104: end 105: until conn = acquire(t, server) 106: raise(::Sequel::PoolTimeout) if Time.new > timeout 107: sleep sleep_time 108: end 109: begin 110: yield conn 111: rescue Sequel::DatabaseDisconnectError => dde 112: remove(t, conn, server) 113: raise 114: ensure 115: release(t, conn, server) unless dde 116: end 117: rescue Exception => e 118: raise(@convert_exceptions && !e.is_a?(StandardError) ? RuntimeError.new(e.message) : e) 119: end 120: end