Amp\Mysql\ConnectionPool::addConnection PHP Method

    public function addConnection()
    {
        \Amp\immediately(function () {
            if (count($this->connections) >= $this->limit) {
                return;
            }
            $this->connections[] = $conn = new Connection($this->config);
            end($this->connections);
            $this->connectionMap[spl_object_hash($conn)] = key($this->connections);
            $this->connectionPromise = $conn->connect();
            $this->connectionPromise->when(function ($error) use($conn) {
                if ($error) {
                    $this->unmapConnection($conn);
                    if (empty($this->connections)) {
                        $this->virtualConnection->fail($error);
                    }
                    return;
                }
                if ($this->config->charset != "utf8mb4" || $this->config->collate != "" && $this->config->collate != "utf8mb4_general_ci") {
                    $conn->setCharset($this->config->charset, $this->config->collate);
                }
            });
        });
    }