Semian

Inspired by the bulkhead resource isolation pattern used in Hystrix, Semian aims to provide a Ruby API that can be used to control access to external resources.

This can be used with a forking Ruby application server like Unicorn to prevent app server starvation when a resource is slow or not responding.

Usage

In a master process, register a resource with a specified number of tickets (number of concurrent clients):

require 'semian'

Semian.register(:mysql_master, tickets: 3, timeout: 0.5)

Then in your child processes, you can use the resource:

Semian[:mysql_master].acquire do
    # Query mysql and do things
end

If you have a process that does not fork, you can still use the same namespace to control access to a shared resource:

Semian.register(:mysql_master, timeout: 0.5)
Semian[:mysql_master].acquire do
    # Query mysql and do things
end