Not buffering unix socket packets.

[cloudflare]

Not buffering unix socket packets.

[agentzh]

@robholland Unix domain sockets are not free of overhead. Writing to such sockets also involve an expensive send system call. If every request trigger such an expensive system call, it will have a big impact on the system's overall throughput. And you can always disable the buffering yourself by configuring flush_limit = 1 in your own Lua code anyway :)

[robholland]

The trouble is, certainly with syslog, it's not valid to write more than exactly one log message per packet. So saving up such calls doesn't gain you anything I don't think, you still need to make the same number of syscalls.

[agentzh]

@robholland Sorry, I was talking about the stream typed unix domain sockets. If you are using unix domain sockets of the datagram type, then you have to issue separate send system call to send each message in individual datagram. So this mode could be quite expensive. (Also, ngx_lua does not support datagram unix domain socket pooling, so it could also require an extra socket system call at least).

Even for datagram typed unix domain socket, message buffering can save a lot of ngx.timer.at calls and their associated light threads' overhead, and also approximate socket pooling.

[robholland]

Ok, so it should be left as it was in the patch buffering wise, and allow people to control it with flush limit = 1 as they like.

Unfortunately datagram based sockets are the only option for logging to /dev/log on some linux distributions.

Closing, thanks.