DEV: s/\$redis/Discourse\.redis (#8431)

This commit also adds a rubocop rule to prevent global variables.

app/models/concerns/cached_counting.rb

@@ -19,13 +19,13 @@ module CachedCounting
 
   class_methods do
     def perform_increment!(key, opts = nil)
-      val = $redis.incr(key).to_i
+      val = Discourse.redis.incr(key).to_i
 
       # readonly mode it is going to be 0, skip
       return if val == 0
 
       # 3.days, see: https://github.com/rails/rails/issues/21296
-      $redis.expire(key, 259200)
+      Discourse.redis.expire(key, 259200)
 
       autoflush = (opts && opts[:autoflush]) || self.autoflush
       if autoflush > 0 && val >= autoflush
@@ -51,9 +51,9 @@ module CachedCounting
     # this may seem a bit fancy but in so it allows
     # for concurrent calls without double counting
     def get_and_reset(key)
-      namespaced_key = $redis.namespace_key(key)
-      val = $redis.without_namespace.eval(GET_AND_RESET, keys: [namespaced_key]).to_i
-      $redis.expire(key, 259200) # SET removes expiry, so set it again
+      namespaced_key = Discourse.redis.namespace_key(key)
+      val = Discourse.redis.without_namespace.eval(GET_AND_RESET, keys: [namespaced_key]).to_i
+      Discourse.redis.expire(key, 259200) # SET removes expiry, so set it again
       val
     end
 

app/models/concerns/stats_cacheable.rb

@@ -19,7 +19,7 @@ module StatsCacheable
 
     def fetch_cached_stats
       # The scheduled Stats job is responsible for generating and caching this.
-      stats = $redis.get(stats_cache_key)
+      stats = Discourse.redis.get(stats_cache_key)
       stats = refresh_stats if !stats
       JSON.parse(stats).with_indifferent_access
     end
@@ -35,7 +35,7 @@ module StatsCacheable
     def set_cache(stats)
       # Add some extra time to the expiry so that the next job run has plenty of time to
       # finish before previous cached value expires.
-      $redis.setex stats_cache_key, (recalculate_stats_interval + 5).minutes, stats
+      Discourse.redis.setex stats_cache_key, (recalculate_stats_interval + 5).minutes, stats
     end
   end
 end