I am analyzing what is the slimmest configuration in an Ubuntu Server to run my Rails 3.2.6 application with the lowest memory footprint with the Nginx + Unicorn configuration. And using a local postgres database.
After removing many services like whoopsie and apparmor in ubuntu, and let only the very basic processes I can instantiate my workers in both sides, nginx and unicorn for a total of 500MB.
This is purely the vanilla launch of the app. with a single database connection.
This is the result of the commands executed to baseline with the first user:
$ free -mt
total used free shared buffers cached
Mem: 3001 550 2450 0 16 178
-/+ buffers/cache: 355 2646
Swap: 952 0 952
Total: 3954 550 3403
$ ps -ef | grep nginx
root 1232 1 0 12:54 ? 00:00:00 nginx: master process /usr/sbin/nginx
www-data 1233 1232 0 12:54 ? 00:00:00 nginx: worker process
www-data 1234 1232 0 12:54 ? 00:00:00 nginx: worker process
www-data 1235 1232 0 12:54 ? 00:00:00 nginx: worker process
www-data 1236 1232 0 12:54 ? 00:00:00 nginx: worker process
herminio 5292 1078 0 13:24 pts/1 00:00:00 grep nginx
$ ps -ef | grep unicorn
herminio 4863 1 0 13:01 ? 00:00:00 unicorn_rails master -c unicorn.rb -D -E production
herminio 4866 4863 2 13:01 ? 00:00:34 unicorn_rails worker[0] -c unicorn.rb -D -E production
herminio 5296 1078 0 13:24 pts/1 00:00:00 grep unicorn
$ ps -ef | grep postg
postgres 935 1 0 12:54 ? 00:00:00 /usr/lib/postgresql/9.1/bin/postgres -D /var/lib/postgresql/9.1/main -c config_file=/etc/postgresql/9.1/main/postgresql.conf
postgres 940 935 0 12:54 ? 00:00:00 postgres: writer process
postgres 941 935 0 12:54 ? 00:00:00 postgres: wal writer process
postgres 942 935 0 12:54 ? 00:00:00 postgres: autovacuum launcher process
postgres 943 935 0 12:54 ? 00:00:00 postgres: stats collector process
postgres 5215 935 0 13:12 ? 00:00:00 postgres: user_db pto_db_prod 127.0.0.1(47118) idle
herminio 5300 1078 0 13:24 pts/1 00:00:00 grep postg
With this information I can determine that my OS uses 92 processes to host my application with 1 connection, as more processes are spawn from Nginx and Unicorn the number of processes increase +1 and also the connections to the database.
Looking into the memory usage per process can also help to determine the amount of memory consumption of your application.
I am using an old laptop to baseline my app, and it only has 3GB of memory.
In the future I am planning to release this app, in a distributed environment with low spec servers, therefore I want to know specifically the footprint of everything in my rails app.
Some of the things I learn along the way are:
bundle install --without development test # To make sure your app uses and loads Gems that are only used in the production environment and not more.
Make sure you only load the ActiveRecord models that your request needs and not more.
