bradford <[email protected]> wrote: > I'm using unicorn w/ a rails app. I have the following in my > environment.rb $redis = MyApplication::Application.config.redis and in > production.rb I have config.redis = Redis.new(host: "localhost"). > > I've read I'm supposed to $redis = Redis.new(host: "localhost") in > after_fork when preload_app is true. > > When I don't do this, each worker/pid seems to have their own redis > instance. So, why is this needed? Here's the logs of me printing out > $redis.client.inspect when both $redis = Redis.new in the after_fork > and just $redis = Redis.new in the environment.rb.
(Disclaimer: I still haven't used Redis, but similar knowledge applies to every TCP-based service) If a Redis client opens a TCP (or any stream) socket connection before forking, all the children that are forked will share that _same_ local TCP socket. Sharing stream sockets across processes/threads is nearly always a bad idea: data streams become interleaved and impossible to separate in either direction. > No after fork > https://gist.github.com/bc2c2a3bda01c35730e2 > > After fork > https://gist.github.com/0c96550660d3926ffe16 > > The only thing different I notice is Connection::TCPSocket:fd is > always 13 w/ the after fork. FD shouldn't really matter. FDs get recycled ASAP once they're closed (and GC can automatically close them). What you want is a different local port for the TCPSocket on every worker process, and the after_fork hook will give you that. Btw, you can demonstrate FD recycling with: require 'socket' loop do c = TCPSocket.new("example.com", 80) p [ :fileno, c.fileno ] p [ :addr, c.addr ] # (local address) c.close sleep 1 # be nice to the remote server end You'll see the same FD recycled over and over, but c.addr will have a different local port. You can see if after_fork is working correctly by checking the output of tools like `ss' or `netstat': (something like: ss -tan | grep -F :$PORT_OF_REDIS) You can also check connections on the Redis server/process itself using "lsof -p $PID_OF_REDIS_DAEMON" _______________________________________________ Unicorn mailing list - [email protected] http://rubyforge.org/mailman/listinfo/mongrel-unicorn Do not quote signatures (like this one) or top post when replying
