背景：项目中需要在抓取纷享销客CRM图片上传到OSS,调用OssClient.php时，容易发生解析超时(多重试几次就ok)。

错误提示：

[2019-04-08 19:41:01] lumen.DEBUG: 出错文件：/home/zrj/www/admin/yundou-admin/vendor/aliyuncs/oss-sdk-php/src/OSS/OssClient.php  
[2019-04-08 19:41:01] lumen.DEBUG: 出错编码：0  
[2019-04-08 19:41:01] lumen.DEBUG: 出错行号：2187  
[2019-04-08 19:41:01] lumen.DEBUG: 出错信息：RequestCoreException: cURL resource: Resource id #371; cURL error: Resolving timed out after 10521 milliseconds (28) 

Resolving timed out after 10521 milliseconds (28)
解析超时

源码分析:

try {
            $ossClient = new OssClient(self::$accessKeyId, self::$accessKeySecret, self::$endpoint);
            $ossClient->uploadFile(self::$bucket, $ossFileName, $localhostFileName);//上传文件
            $ossClient->putBucketAcl(self::$bucket, OssClient::OSS_ACL_TYPE_PUBLIC_READ);
        } catch (OssException $e) {
            self::debugException($e);
            throw new \Exception("上传oss失败:" . $e->getMessage(), $e->getCode());
        }

1.实例化OssClient客户端后，调用uploadFile方法。
2.uploadFile调用了auth,验证并且执行请求，按照OSS Api协议，执行操作。

    /**
     * 上传本地文件
     *
     * @param string $bucket bucket名称
     * @param string $object object名称
     * @param string $file 本地文件路径
     * @param array $options
     * @return null
     * @throws OssException
     */
    public function uploadFile($bucket, $object, $file, $options = NULL)
    {
        ......
        $response = $this->auth($options);
        $result = new PutSetDeleteResult($response);
        return $result->getData();
    }

3.auth中调用RequestCore类创建请求

    /**
     * 验证并且执行请求，按照OSS Api协议，执行操作
     *
     * @param array $options
     * @return ResponseCore
     * @throws OssException
     * @throws RequestCore_Exception
     */
    private function auth($options)
    {
            ......
        //创建请求
        $request = new RequestCore($this->requestUrl, $this->requestProxy);
        $request->set_useragent($this->generateUserAgent());
                ......
                try {
            $request->send_request();
        } catch (RequestCore_Exception $e) {
            throw(new OssException('RequestCoreException: ' . $e->getMessage()));
        }
    }

4.OSS\Http\RequestCore类中send_request方法通过CURL发送请求(调用了prep_request准备请求方法)

 /**
     * Sends the request, calling necessary utility functions to update built-in properties.
     *
     * @param boolean $parse (Optional) Whether to parse the response with ResponseCore or not.
     * @return string The resulting unparsed data from the request.
     */
    public function send_request($parse = false)
    {
        set_time_limit(0);

        $curl_handle = $this->prep_request();
        $this->response = curl_exec($curl_handle);

        if ($this->response === false) {
            throw new RequestCore_Exception('cURL resource: ' . (string)$curl_handle . '; cURL error: ' . curl_error($curl_handle) . ' (' . curl_errno($curl_handle) . ')');
        }

        $parsed_response = $this->process_response($curl_handle, $this->response);

        curl_close($curl_handle);

        if ($parse) {
            return $parsed_response;
        }

        return $this->response;
    }

5.最终可以推导出问题出在RequestCore中的CURL。

解决方案：
curl有一个CURLOPT_IPRESOLVE选项，作用是指定使用那种IP协议(IPV4/IPV6)。

CURLOPT_IPRESOLVE - specify which IP protocol version to use

选项：
CURL_IPRESOLVE_WHATEVER

Default, resolves addresses to all IP versions that your system allows.

CURL_IPRESOLVE_V4

Resolve to IPv4 addresses.

CURL_IPRESOLVE_V6

Resolve to IPv6 addresses.

这里要注意：默认值（curl没有主动设置CURLOPT_IPRESOLVE选项时，则系统会使用默认值）。

Default, resolves addresses to all IP versions that your system allows.

含义为：默认使用服务器系统允许的所有IP版本来解析地址。
而服务器系统可能存在同时支持IPV4/IPV6,CURL会挨个去试。当本地网络不支持其中任何一种IP版本协议时，会出现超时。

所以，最终的解决方案为显式指定CURL的CURLOPT_IPRESOLVE选项。

curl_setopt($ch, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);

参考官方CURLOPT_IPRESOLVE