File IO isn’t epoll-able. The operations are always blocking. Those could however be offloaded onto a threadpool, to avoid the blocking to affect any other req

File IO isn’t epoll-able. The operations are always blocking. Those could however be offloaded onto a threadpool, to avoid the blocking to affect any other requests that are processed by the same Nginx worker. Nginx however only partially does that - whole file read and write operations are offloaded a whole bunch of other IO (stat, open, close) are executed on the main thread. I guess due to implementation challenges - one can’t just make one operation async but also needs to make each operation that utilizes those methods async.