ConnectionPool

The proc used to create a new connection.

The maximum number of connections.

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 poolconnection_proc.

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

# File lib/assistance/connection_pool.rb, line 27
def initialize(max_size = 4, &block)
  @max_size = max_size
  @mutex = Mutex.new
  @connection_proc = block

  @available_connections = []
  @allocated = {}
  @created_count = 0
end

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.

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

# File lib/assistance/connection_pool.rb, line 52
def hold
  t = Thread.current
  if (conn = owned_connection(t))
    return yield(conn)
  end
  while !(conn = acquire(t))
    sleep 0.001
  end
  begin
    yield conn
  ensure
    release(t)
  end
rescue Exception => e
  # if the error is not a StandardError it is converted into RuntimeError.
  raise e.is_a?(StandardError) ? e : e.message
end

Returns the number of created connections.

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