DEV: Consolidate Redis evalsha logic into DiscourseRedis::EvalHelper (#15957)

lib/discourse_redis.rb

@@ -161,4 +161,20 @@ class DiscourseRedis
     key[(namespace.length + 1)..-1]
   end
 
+  class EvalHelper
+    def initialize(script)
+      @script = script
+      @sha1 = Digest::SHA1.hexdigest(script)
+    end
+
+    def eval(redis, *args, **kwargs)
+      redis.evalsha @sha1, *args, **kwargs
+    rescue ::Redis::CommandError => e
+      if e.to_s =~ /^NOSCRIPT/
+        redis.eval @script, *args, **kwargs
+      else
+        raise
+      end
+    end
+  end
 end

lib/middleware/anonymous_cache.rb

@@ -49,6 +49,12 @@ module Middleware
       ACCEPT_ENCODING  = "HTTP_ACCEPT_ENCODING"
       DISCOURSE_RENDER = "HTTP_DISCOURSE_RENDER"
 
+      REDIS_STORE_SCRIPT = DiscourseRedis::EvalHelper.new <<~LUA
+        local current = redis.call("incr", KEYS[1])
+        redis.call("expire",KEYS[1],ARGV[1])
+        return current
+      LUA
+
       def initialize(env, request = nil)
         @env = env
         @request = request || Rack::Request.new(@env)
@@ -259,11 +265,7 @@ module Middleware
         if status == 200 && cache_duration
 
           if GlobalSetting.anon_cache_store_threshold > 1
-            count = Discourse.redis.eval(<<~REDIS, [cache_key_count], [cache_duration])
-              local current = redis.call("incr", KEYS[1])
-              redis.call("expire",KEYS[1],ARGV[1])
-              return current
-            REDIS
+            count = REDIS_STORE_SCRIPT.eval(Discourse.redis, [cache_key_count], [cache_duration])
 
             # technically lua will cast for us, but might as well be
             # prudent here, hence the to_i

lib/presence_channel.rb

@@ -260,15 +260,7 @@ class PresenceChannel
   end
 
   def self.redis_eval(key, *args)
-    script_sha1 = LUA_SCRIPTS_SHA1[key]
-    raise ArgumentError.new("No script for #{key}") if script_sha1.nil?
-    redis.evalsha script_sha1, *args
-  rescue ::Redis::CommandError => e
-    if e.to_s =~ /^NOSCRIPT/
-      redis.eval LUA_SCRIPTS[key], *args
-    else
-      raise
-    end
+    LUA_SCRIPTS[key].eval(redis, *args)
   end
 
   # Register a callback to configure channels with a given prefix
@@ -473,7 +465,7 @@ class PresenceChannel
 
   LUA_SCRIPTS ||= {}
 
-  LUA_SCRIPTS[:present] = <<~LUA
+  LUA_SCRIPTS[:present] = DiscourseRedis::EvalHelper.new <<~LUA
     #{COMMON_PRESENT_LEAVE_LUA}
 
     if mutex_locked then
@@ -502,7 +494,7 @@ class PresenceChannel
     return added_users
   LUA
 
-  LUA_SCRIPTS[:leave] = <<~LUA
+  LUA_SCRIPTS[:leave] = DiscourseRedis::EvalHelper.new <<~LUA
     #{COMMON_PRESENT_LEAVE_LUA}
 
     if mutex_locked then
@@ -532,7 +524,7 @@ class PresenceChannel
     return removed_users
   LUA
 
-  LUA_SCRIPTS[:release_mutex] = <<~LUA
+  LUA_SCRIPTS[:release_mutex] = DiscourseRedis::EvalHelper.new <<~LUA
     local mutex_key = KEYS[1]
     local expected_value = ARGV[1]
 
@@ -541,7 +533,7 @@ class PresenceChannel
     end
   LUA
 
-  LUA_SCRIPTS[:user_ids] = <<~LUA
+  LUA_SCRIPTS[:user_ids] = DiscourseRedis::EvalHelper.new <<~LUA
     local zlist_key = KEYS[1]
     local hash_key = KEYS[2]
     local message_bus_id_key = KEYS[4]
@@ -562,7 +554,7 @@ class PresenceChannel
     return { message_bus_id, user_ids }
   LUA
 
-  LUA_SCRIPTS[:count] = <<~LUA
+  LUA_SCRIPTS[:count] = DiscourseRedis::EvalHelper.new <<~LUA
     local zlist_key = KEYS[1]
     local hash_key = KEYS[2]
     local message_bus_id_key = KEYS[4]
@@ -582,7 +574,7 @@ class PresenceChannel
     return { message_bus_id, count }
   LUA
 
-  LUA_SCRIPTS[:auto_leave] = <<~LUA
+  LUA_SCRIPTS[:auto_leave] = DiscourseRedis::EvalHelper.new <<~LUA
     local zlist_key = KEYS[1]
     local hash_key = KEYS[2]
     local channels_key = KEYS[3]
@@ -626,9 +618,4 @@ class PresenceChannel
 
     return expired_user_ids
   LUA
-  LUA_SCRIPTS.freeze
-
-  LUA_SCRIPTS_SHA1 = LUA_SCRIPTS.transform_values do |script|
-    Digest::SHA1.hexdigest(script)
-  end.freeze
 end

lib/rate_limiter.rb

@@ -70,7 +70,7 @@ class RateLimiter
 
   # reloader friendly
   unless defined? PERFORM_LUA
-    PERFORM_LUA = <<~LUA
+    PERFORM_LUA = DiscourseRedis::EvalHelper.new <<~LUA
       local now = tonumber(ARGV[1])
       local secs = tonumber(ARGV[2])
       local max = tonumber(ARGV[3])
@@ -89,12 +89,10 @@ class RateLimiter
         return 0
       end
     LUA
-
-    PERFORM_LUA_SHA = Digest::SHA1.hexdigest(PERFORM_LUA)
   end
 
   unless defined? PERFORM_LUA_AGGRESSIVE
-    PERFORM_LUA_AGGRESSIVE = <<~LUA
+    PERFORM_LUA_AGGRESSIVE = DiscourseRedis::EvalHelper.new <<~LUA
       local now = tonumber(ARGV[1])
       local secs = tonumber(ARGV[2])
       local max = tonumber(ARGV[3])
@@ -116,8 +114,6 @@ class RateLimiter
 
       return return_val
     LUA
-
-    PERFORM_LUA_AGGRESSIVE_SHA = Digest::SHA1.hexdigest(PERFORM_LUA_AGGRESSIVE)
   end
 
   def performed!(raise_error: true)
@@ -161,15 +157,9 @@ class RateLimiter
 
   def rate_limiter_allowed?(now)
     lua, lua_sha = nil
-    if @aggressive
-      lua = PERFORM_LUA_AGGRESSIVE
-      lua_sha = PERFORM_LUA_AGGRESSIVE_SHA
-    else
-      lua = PERFORM_LUA
-      lua_sha = PERFORM_LUA_SHA
-    end
+    eval_helper = @aggressive ? PERFORM_LUA_AGGRESSIVE : PERFORM_LUA
 
-    eval_lua(lua, lua_sha, [prefixed_key], [now, @secs, @max]) == 0
+    eval_helper.eval(redis, [prefixed_key], [now, @secs, @max]) == 0
   end
 
   def prefixed_key
@@ -201,14 +191,4 @@ class RateLimiter
   def rate_unlimited?
     !!(RateLimiter.disabled? || (@user&.staff? && !@apply_limit_to_staff && @staff_limit[:max].nil?))
   end
-
-  def eval_lua(lua, sha, keys, args)
-    redis.evalsha(sha, keys, args)
-  rescue Redis::CommandError => e
-    if e.to_s =~ /^NOSCRIPT/
-      redis.eval(lua, keys, args)
-    else
-      raise
-    end
-  end
 end

spec/components/discourse_redis_spec.rb

@@ -132,4 +132,49 @@ describe DiscourseRedis do
       end
     end
   end
+
+  describe DiscourseRedis::EvalHelper do
+    it "works" do
+      helper = DiscourseRedis::EvalHelper.new <<~LUA
+        return 'hello world'
+      LUA
+      expect(helper.eval(Discourse.redis)).to eq('hello world')
+    end
+
+    it "works with arguments" do
+      helper = DiscourseRedis::EvalHelper.new <<~LUA
+        return ARGV[1]..ARGV[2]..KEYS[1]..KEYS[2]
+      LUA
+      expect(helper.eval(Discourse.redis, ['key1', 'key2'], ['arg1', 'arg2'])).to eq("arg1arg2key1key2")
+    end
+
+    it "works with arguments" do
+      helper = DiscourseRedis::EvalHelper.new <<~LUA
+        return ARGV[1]..ARGV[2]..KEYS[1]..KEYS[2]
+      LUA
+      expect(helper.eval(Discourse.redis, ['key1', 'key2'], ['arg1', 'arg2'])).to eq("arg1arg2key1key2")
+    end
+
+    it "uses evalsha correctly" do
+      redis_proxy = Class.new do
+        attr_reader :calls
+        def method_missing(meth, *args, **kwargs, &block)
+          @calls ||= []
+          @calls.push(meth)
+          Discourse.redis.public_send(meth, *args, **kwargs, &block)
+        end
+      end.new
+
+      Discourse.redis.call("SCRIPT", "FLUSH", "SYNC")
+
+      helper = DiscourseRedis::EvalHelper.new <<~LUA
+        return 'hello world'
+      LUA
+      expect(helper.eval(redis_proxy)).to eq("hello world")
+      expect(helper.eval(redis_proxy)).to eq("hello world")
+      expect(helper.eval(redis_proxy)).to eq("hello world")
+
+      expect(redis_proxy.calls).to eq([:evalsha, :eval, :evalsha, :evalsha])
+    end
+  end
 end