List of yielding API calls

rpaprocki · 2016-06-29T08:46:21+00:00

You haven't told us anything about your existing load-balanced setup or how you expect your Nginx server to receive that data, so it's doubtful we...

List of yielding API calls

rpaprocki

Hey folks,

We all know about the perils/joy of sharing data via the module-level variables (https://github.com/openresty/lua-nginx-module#data-sharing-within-an-nginx-worker). And as such, writeable data can be -carefully- shared via this method, provided that the light thread doesn't give back control to the scheduler. My question is, is there a solid list of APi calls that would give control back to the scheduler? The docs for thread.spawn allude to this, but seems incomplete. I can think of:

location.capture

socket operations (duh)

thread.spawn/thread.yield (also duh)

redirect

send_headers

say

flush

exit

exec

req.set_uri

sleep

update_time (maybe?)

coroutine

semaphore

Anyone spot anything I'm missing?

agentzh

Hello!

On Tue, Jun 28, 2016 at 5:46 PM, Robert Paprocki wrote:
> We all know about the perils/joy of sharing data via the module-level
> variables
> (https://github.com/openresty/lua-nginx-module#data-sharing-within-an-nginx-worker).
> And as such, writeable data can be -carefully- shared via this method,
> provided that the light thread doesn't give back control to the scheduler.
> My question is, is there a solid list of APi calls that would give control
> back to the scheduler? The docs for thread.spawn allude to this, but seems
> incomplete. I can think of:

Yeah, this is a good idea to add a "May yield" tag to the API docs for
each API function.

Patches welcome :)

>
> send_headers
> print
> say

These do not yield.

> flush

Only when the true argument is specified.

> req.set_uri

Only when the jump argument is true.

> update_time (maybe?)

This never yields.

The best way to be sure is to search for the "yield" word in the API's
implementation source code :)

Best regards,
-agentzh