Grow Redis conn pool size with Puma thread count

config/application.rb

@@ -255,8 +255,8 @@ module Gitlab
     caching_config_hash[:compress] = false
     caching_config_hash[:namespace] = Gitlab::Redis::Cache::CACHE_NAMESPACE
     caching_config_hash[:expires_in] = 2.weeks # Cache should not grow forever
-    if Sidekiq.server? # threaded context
-      caching_config_hash[:pool_size] = Sidekiq.options[:concurrency] + 5
+    if Sidekiq.server? || defined?(::Puma) # threaded context
+      caching_config_hash[:pool_size] = Gitlab::Redis::Cache.pool_size
       caching_config_hash[:pool_timeout] = 1
     end
 

lib/gitlab/redis/wrapper.rb

@@ -25,6 +25,8 @@ module Gitlab
           if Sidekiq.server?
             # the pool will be used in a multi-threaded context
             size += Sidekiq.options[:concurrency]
+          elsif defined?(::Puma)
+            size += Puma.cli_config.options[:max_threads]
           end
 
           size