Hi, On Mon, Feb 07, 2022 at 01:27:15PM +0100, Jiří Setnička via nginx-devel wrote: > Hello, > > > Thanks for sharing your work. Indeed, nginx currently lacks a good solution > > for serving a file that's being downloaded from upstream. We tried to > > address > > this issue a few years ago. Our solution was similar to yours, but instead > > of sharing the temp file between workers, we moved the temp file to its > > destination right after writing the header. A new bit was added to the > > header > > signalling that this file is being updated. > > > > The biggest issue with this kind of solutions is how we wait for updates in > > a file. We believe that polling a file with a given time interval is not a > > perfect approach, even though nginx does that for cache locks. > > polling is done only on the ngx_http_file_cache_tf_node_t struct in the > shared memory (see patch 09 of 15, where c->length is updated from > c->tf_node->length and then this length is compared with > c->body_sent_bytes), not on the file itself. Length in the tf_node is > updated with each write from the primary request (see patch 05 of 15). > > It is better than polling individual files, but I agree it is still polling, > which isn't great. > > > [...] > > Another approach would be to create an > > inter-worker messaging system for signalling file updates. > > We were thinking about creating something like that but we buried this idea > because it seems quite complex to do it right and reliable. And polling the > tf_node in the shared memory (with very low proxy_cache_tempfile_loop) works > sufficiently good. > > > > It's good to know the solution works for you. Please keep us posted about > > future improvements especially the ones which would avoid polling and > > decrease > > complexity. > > We would be happy to get this patch to the mainline nginx in the future, so > that all nginx users could benefit from it. > > We will be thinking about avoiding polling and implementing some > inter-worker messaging, but it may be some time, because it seems quite > complex. Could you share some hints about how do you thing it would be best > to implement it in the worker's event loop?
Even though I have some ideas, they need to be checked first. I can only say this should be a core nginx feature. > Jiří Setnička > CDN77 > > _______________________________________________ > nginx-devel mailing list -- nginx-devel@nginx.org > To unsubscribe send an email to nginx-devel-le...@nginx.org -- Roman Arutyunyan _______________________________________________ nginx-devel mailing list -- nginx-devel@nginx.org To unsubscribe send an email to nginx-devel-le...@nginx.org
