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 variables. 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 = Integer(opts[:max_connections] || 4) 45: raise(Sequel::Error, ':max_connections must be positive') if @max_size < 1 46: @mutex = Mutex.new 47: @connection_proc = block 48: @disconnection_proc = opts[:disconnection_proc] 49: @servers = [:default] 50: @servers += opts[:servers].keys - @servers if opts[:servers] 51: @available_connections = Hash.new{|h,k| h[:default]} 52: @allocated = Hash.new{|h,k| h[:default]} 53: @servers.each do |s| 54: @available_connections[s] = [] 55: @allocated[s] = {} 56: end 57: @timeout = Integer(opts[:pool_timeout] || 5) 58: @sleep_time = Float(opts[:pool_sleep_time] || 0.001) 59: @convert_exceptions = opts.include?(:pool_convert_exceptions) ? opts[:pool_convert_exceptions] : true 60: 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 64 64: def allocated(server=:default) 65: @allocated[server] 66: end
An array of connections opened but not currently used, for the given server.
# File lib/sequel/connection_pool.rb, line 70 70: def available_connections(server=:default) 71: @available_connections[server] 72: 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 76 76: def created_count(server=:default) 77: @allocated[server].length + @available_connections[server].length 78: 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 131 131: def disconnect(&block) 132: block ||= @disconnection_proc 133: @mutex.synchronize do 134: @available_connections.each do |server, conns| 135: conns.each{|c| block.call(c)} if block 136: conns.clear 137: end 138: end 139: 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 95 95: def hold(server=:default) 96: begin 97: t = Thread.current 98: if conn = owned_connection(t, server) 99: return yield(conn) 100: end 101: begin 102: unless conn = acquire(t, server) 103: time = Time.new 104: timeout = time + @timeout 105: sleep_time = @sleep_time 106: sleep sleep_time 107: until conn = acquire(t, server) 108: raise(::Sequel::PoolTimeout) if Time.new > timeout 109: sleep sleep_time 110: end 111: end 112: yield conn 113: rescue Sequel::DatabaseDisconnectError => dde 114: remove(t, conn, server) if conn 115: raise 116: ensure 117: @mutex.synchronize{release(t, server)} if conn && !dde 118: end 119: rescue StandardError 120: raise 121: rescue Exception => e 122: raise(@convert_exceptions ? RuntimeError.new(e.message) : e) 123: end 124: end