HTTPS PHP大型XML有效负载无法通过echo到达客户端

Our web service is experiencing a big issue with some clients. The web service is a PHP script under SSL which uses GET parameters to configure multiple heavy queries on a MySQL database and returns an XML payload. The payload is only 1 MB but processing is very complex and takes about 5-6 minutes to finish. Clients are iPad running a specific application. Sometimes, and on some networks, the client does not receive the payload and keep waiting until timeout. We started logging everything on our server. A normal response_ssl reports about 290 seconds to serve the payload, but when the issue occurs we can see 900 seconds for the same payload. However, even after 900 seconds the client does not receive the payload.Our web service is experiencing a big issue wit