如何拥有线程安全的Rails初始化器？

Question

I am thinking about switching my Rails app to Sidekiq and Puma when my app gets some significant load. However, they require the app to be thread-safe.

One of the things that are typically considered not thread-safe are global variables. But my app uses a common pattern found in Rails apps and tutorials, where you define global variables in initializers like so:

# config/initializers/aws.rb
...
$s3_bucket = Aws::S3::Resource.new.bucket(ENV['AWS_S3_BUCKET'])

# config/initializers/mixpanel.rb
$mixpanel = Mixpanel::Tracker.new(ENV['MIXPANEL_TOKEN']) do |*message|
  ...
end

# config/initializers/redis.rb
$redis = Redis.new(host: ENV['REDIS_HOST'], port: ENV['REDIS_PORT'])

# config/initializers/twilio.rb
$twilio_client = Twilio::REST::Client.new(ENV['TWILIO_ACCOUNT_SID'], ENV['TWILIO_AUTH_TOKEN'])

I like this approach because the rest of the codebase can use these variables very easily, and it makes it is terser.

But are these global variables thread-safe? If not, what are my options? I would preferably use a solution that still keeps the codebase easy to read.

Answer 1

Initializers are run in the main thread before other threads are created. They can be thread-unsafe.

A better solution would be to either instantiate mixpanel/twilio_client/etc every time before using them, or use a connection pool.