I need to send large (300k) HTTP responses from my Mongoose OS/ESP32 based application. I don’t have 300k contiguous free heap available.
It appears that all the mg_send_* calls buffer into memory (when servicing the HTTP request, I get the E:M log messages indicating that along the line an attempt is being made to allocate > 83000 bytes).
Is there a way to get Mongoose to send the response in smaller pieces?
Yes, check the send_iobuf length before mg_send_, and if it is larger than some reasonable threshold, do not send but rather wait for another poll cycle. This is what default file handler does.
See https://github.com/cesanta/mongoose/blob/master/src/mg_http.c
Function mg_http_transfer_file_data()
ok, that makes perfect sense.
I see mg_http_transfer_file_data getting called at the beginning of the transfer (line 1549 on the current commit), and when EV_CLOSE is received (routine mg_http_handler, line 779). The latter surprises me; I would expect that call to mg_http_transfer_file_data to happen when EV_POLL or EV_SEND are received?
also, the http handler I registered with mgos_register_http_endpoint does not seem to get EV_POLL or EV_SEND events (or any events except the HTTP events). How do I detect the lower level events?
does anyone have any insight to lend here, especially around how to see EV_POLL and EV_SEND events?