How do I configure Apache2 to allow multiple simultaneous connections from same IP address?

Question

By default, Apache2 seems to allow only 1 connection per IP address.

How do I configure Apache2 to allow multiple simultaneous connections from the same IP address?

Here is my situation:

1. a web app being hosted on a server.
2. a remote client makes an request that may take 15 seconds to complete.
3. the same remote client makes another (independent) request.
4. at present, the 2nd request sits in a queue until the 1st request completes, since Apache2 seems to impose a limit of 1 connection per IP address.

How do I override this default behaviour and allow the 2nd request to be processed in parallel?

thanks in advance, David Jones

Solution

I discovered the answer to my problem. It turns out others have encountered this difficulty before:

Simultaneous Requests to PHP Script

The key detail is that file-based sessions in PHP cause all requests from the same client to be processed sequentially in a queue, rather than in parallel.

In order to solve this problem, it is necessary to make a call to session_write_close() in every PHP script as soon as session handling is finished.

-- David Jones