Ruby Server: Multiple gRPC processes

[Andrew Lazarus]

I posted a reply to a python question but I think this deserves its own thread.

MRI's GIL limits each ruby process to a single core. To utilize multiple cores, you need to use multiple processes. To work around this limitation, a "standard" ruby server deploy uses multiple processes listening on a single port or domain socket. Using puma (a threaded HTTP/1.1 server) as an example, here is a standard setup:

nginx accepts external requests: it is configured as a reverse proxy that terminates SSL (SSL termination further helps reduce CPU load on the ruby processes). A puma master process listens on a domain socket or port and then spawns a set of worker processes that actually handle the requests.

There are a couple solutions I can think of for gRPC.

1) nginx as a reverse proxy with N gRPC server processes listening on N different ports. Nginx would terminate SSL in this case. This solution is very sub-optimal since it requires N ports for each service.

2) Same as #1, but use domain sockets. This would require changes to gRPC core so that it can listen on domain sockets in addition to ports. This is preferable to #1.

3) Add a process / socket management layer that listens on a socket then forks gRPC server subprocesses that inherit the parent socket. This seems like the best solution, but is probably the most work. It would require changes to gRPC core + writing the process management layer.

[Craig Tiller]

I've been thinking a little about this recently but haven't had the chance to write anything down. I think there's some big opportunities to support a fork/SO_REUSEPORT style concurrency for core wrapping languages (so #3).

gRPC core can already use UNIX domain sockets. When adding a port use unix:path_to_socket, and similarly when creating a client side channel.

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[Andrew Lazarus]

fork/SO_REUSEPORT support would be awesome. I think the domain sockets will work for now. Will report back after testing with nginx.

[Craig Tiller]

If anyone is looking for a starter project within core I'd be happy to work with them to get SO_REUSEPORT support done.

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[mon...@instacart.com]

I'd be interested in contributing on this front. Has there been any additional movement on this in the last 3 years?