[HTTPD] support for multiple simultaneous requests (try 3) (IDFGH-9868)

[chipweinberger]

Related Issue: #10594

Previous PR: #10669

Add basic support for supporting multiple simultaneous requests in HTTPD server.

This is the 3rd try of this PR:

• 1st: worked well
• 2nd: tried to simplified the user api, but made things too complicated for the server code
• 3rd: went back to the first approach, with slightly cleaner api

Note: This PR does not add automatic support for simultaneous requests, but instead makes it more ergonomic for users to move a request to a thread that they must create themselves.

Advantages over raw sockets

• easier reply: Users can use all the existing httpd functions (i.e. httpd_resp_sendstr) to send their response instead of raw socket send()
• LRU safety: A long running async socket will not get closed from underneath us if we run out of sockets

Implementation:

• an request handler will first call httpd_req_async_handler_begin()
  • this gives the user exclusive use of a new request object (to not interfere with the http server's request)
  • this will mark the socket as "in use" to guarentee the socket to not be LRU purged
• async handler must call httpd_req_async_handler_complete() when done
  • this frees our request object.
  • this will mark the socket as "no longer in use" to allow it to be closed (LRU purged)

Example

• add an example to ESP-IDF, showing usage.

[chipweinberger]

@hmalpani

[hmalpani]

Hello @chipweinberger
This approach looks simpler to me.
Although when I tried these changes, I got into some errors. The program crashed when calling long handler. Can you please check and update the PR accordingly?
Thanks!

[chipweinberger]

Pushed! It works now.

If youre curious the fix, I had introduced a small bug right before pushing. 🤦

in httpd_req_async_handler_begin I was calling a memcpy out of order, overwriting a previous assignment.

[hmalpani]

sha=1289d69870dc5faee84756e168dbacdb59f62a4a

[CLAassistant]

All committers have signed the CLA.

[hmalpani]

Hello @chipweinberger
Can you please sign the CLA agreement. Thanks!

[chipweinberger]

signed

[chipweinberger]

any updates? thanks

[hmalpani]

Hello @chipweinberger
I have created an internal MR which is under review. It will get reflected on GitHub once it gets merged.
Thanks!

[chipweinberger]

perhaps I can split the PR up into 2 to make it reviewed faster? Let me know if that would be better.

1. core changes (which is only a small diff in 4 files)
2. new example

[hmalpani]

perhaps I can split the PR up into 2 to make it reviewed faster? Let me know if that would be better.

1. core changes (which is only a small diff in 4 files)

2. new example

Hello @chipweinberger
The PR is already in review and should not take long before getting merged. So no need to update the PR.
Thanks!

[hmalpani]

PR has been merged into master via commit: 3824eba

Closing this PR.