Class ConnectionPool
In: lib/assistance/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

disconnect   hold   new   size  

Attributes

allocated  [R] 
available_connections  [R] 
connection_proc  [RW]  The proc used to create a new connection.
created_count  [R] 
max_size  [R]  The maximum number of connections.
mutex  [R] 

Public Class methods

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(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(10)
  pool.connection_proc = proc {MyConnection.new(opts)}

[Source]

    # File lib/assistance/connection_pool.rb, line 27
27:   def initialize(max_size = 4, &block)
28:     @max_size = max_size
29:     @mutex = Mutex.new
30:     @connection_proc = block
31: 
32:     @available_connections = []
33:     @allocated = {}
34:     @created_count = 0
35:   end

Public Instance methods

Removes all connection currently available, optionally yielding each connection to the given block. This method has the effect of disconnecting from the database. Once a connection is requested using hold, the connection pool creates new connections to the database.

[Source]

    # File lib/assistance/connection_pool.rb, line 74
74:   def disconnect(&block)
75:     @mutex.synchronize do
76:       @available_connections.each {|c| block[c]} if block
77:       @available_connections = []
78:       @created_count = @allocated.size
79:     end
80:   end

Assigns a connection to the current thread, yielding 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 available, Pool#hold will block until a connection is available.

[Source]

    # File lib/assistance/connection_pool.rb, line 52
52:   def hold
53:     t = Thread.current
54:     if (conn = owned_connection(t))
55:       return yield(conn)
56:     end
57:     while !(conn = acquire(t))
58:       sleep 0.001
59:     end
60:     begin
61:       yield conn
62:     ensure
63:       release(t)
64:     end
65:   rescue Exception => e
66:     # if the error is not a StandardError it is converted into RuntimeError.
67:     raise e.is_a?(StandardError) ? e : e.message
68:   end

Returns the number of created connections.

[Source]

    # File lib/assistance/connection_pool.rb, line 38
38:   def size
39:     @created_count
40:   end

[Validate]