On 7/29/25 20:23, Leonid. wrote:
Hello GNU libmicrohttpd developers,
I want to implement the following using this excellent library:
The application maintains a fixed-size thread pool. Each thread executes
asynchronous non-blocking code. Request processing should NEVER block.
For example (the following explanation describes a single thread's
behavior, but this should apply to all threads):
1. An HTTP request arrives, and MHD invokes the handler callback.
2. Inside this callback, I need to query a database.
3. A synchronous DB query would be slow and inefficient—the
application should process other requests while waiting for the DB response.
4. Instead, I want to make a non-blocking DB request with a
callback: "Dear DB client library, when you receive a response from the
DB, invoke this callback (containing further application logic). For
now, send the SQL query and return immediately."
What I expect from MHD:
- MHD should not wait inside the HTTP handler for a response.
- MHD should remember that this request is pending until the DB
callback (or subsequent logic) triggers an MHD response callback with
the finalized data.
Could you please demonstrate how to implement this with MHD? The
documentation lacks such an example and doesn’t clearly explain how to
achieve this workflow. It would be fantastic if you could add this
example to the documentation.
You should just "suspend" the request while your async DB handler is
running and call "resume" on the request once your DB has provided the
result. Just look for suspend/resume in the manual and see
suspend_resume_epoll.c for an example.
Happy hacking!
Christian
