self.global_max.acquire() #semaphore
try:
    self.lock.acquire()
    local = self.ids[identifier]
    self.lock.release()
    
    if not local.max.acquire(false): # acquire local lock, releasing global lock when waiting
        self.global_max.release()
        local.max.acquire()
        self.global_max.acquire()
    try:
        # we have permission to use a connection
        # check if a connection exists
        local.lock.acquire()
        try:
            if len(local.conns > 0):
                connection = local.conns.pop()
            else:
                # find out if we need to close a connection
                self.lock.acquire()
                try:
                    if total.conns >= max_conns: #we need to close a connection
                        #find oldest connection, close it
                finally:
                    self.lock.release()
                #create new connection
        finally:
            local.lock.release()               
    except:
        local.max.release()            
        raise
except:
    self.global_max.release()
    raise