Returns constant of subscription adapter specified in config/cable.yml. If
the adapter cannot be found, this will default to the Redis adapter. Also
makes sure proper dependencies are required.
# File actioncable/lib/action_cable/server/configuration.rb, line 37
def pubsub_adapter
adapter = (cable.fetch("adapter") { "redis" })
# Require the adapter itself and give useful feedback about
# 1. Missing adapter gems and
# 2. Adapter gems' missing dependencies.
path_to_adapter = "action_cable/subscription_adapter/#{adapter}"
begin
require path_to_adapter
rescue LoadError => e
# We couldn't require the adapter itself. Raise an exception that
# points out config typos and missing gems.
if e.path == path_to_adapter
# We can assume that a non-builtin adapter was specified, so it's
# either misspelled or missing from Gemfile.
raise e.class, "Could not load the '#{adapter}' Action Cable pubsub adapter. Ensure that the adapter is spelled correctly in config/cable.yml and that you've added the necessary adapter gem to your Gemfile.", e.backtrace
# Bubbled up from the adapter require. Prefix the exception message
# with some guidance about how to address it and reraise.
else
raise e.class, "Error loading the '#{adapter}' Action Cable pubsub adapter. Missing a gem it depends on? #{e.message}", e.backtrace
end
end
adapter = adapter.camelize
adapter = "PostgreSQL" if adapter == "Postgresql"
"ActionCable::SubscriptionAdapter::#{adapter}".constantize
end