Fix single Redis connection being used across all threads (#18135)

* Fix single Redis connection being used across all Sidekiq threads

* Fix tests

config/application.rb

@@ -35,6 +35,7 @@ require_relative '../lib/paperclip/response_with_limit_adapter'
 require_relative '../lib/terrapin/multi_pipe_extensions'
 require_relative '../lib/mastodon/snowflake'
 require_relative '../lib/mastodon/version'
+require_relative '../lib/mastodon/rack_middleware'
 require_relative '../lib/devise/two_factor_ldap_authenticatable'
 require_relative '../lib/devise/two_factor_pam_authenticatable'
 require_relative '../lib/chewy/strategy/custom_sidekiq'
@@ -164,6 +165,7 @@ module Mastodon
 
     config.middleware.use Rack::Attack
     config.middleware.use Rack::Deflater
+    config.middleware.use Mastodon::RackMiddleware
 
     config.to_prepare do
       Doorkeeper::AuthorizationsController.layout 'modal'

config/initializers/redis.rb

@@ -1,14 +0,0 @@
-# frozen_string_literal: true
-
-redis_connection = Redis.new(
-  url: ENV['REDIS_URL'],
-  driver: :hiredis
-)
-
-namespace = ENV.fetch('REDIS_NAMESPACE') { nil }
-
-if namespace
-  Redis.current = Redis::Namespace.new(namespace, redis: redis_connection)
-else
-  Redis.current = redis_connection
-end

config/initializers/sidekiq.rb

@@ -1,12 +1,12 @@
 # frozen_string_literal: true
 
-require_relative '../../lib/sidekiq_error_handler'
+require_relative '../../lib/mastodon/sidekiq_middleware'
 
 Sidekiq.configure_server do |config|
   config.redis = REDIS_SIDEKIQ_PARAMS
 
   config.server_middleware do |chain|
-    chain.add SidekiqErrorHandler
+    chain.add Mastodon::SidekiqMiddleware
   end
 
   config.server_middleware do |chain|