From df62407f3506f1000625bb91dfbf8fe81a44c91d Mon Sep 17 00:00:00 2001
From: Guo Xiang Tan <gxtan1990@gmail.com>
Date: Mon, 1 Jun 2020 11:20:20 +0800
Subject: [PATCH] DEV: Implement multiple keys support for
 `DiscourseRedis#exists`.

---
 lib/discourse.rb                        |  2 +-
 lib/discourse_redis.rb                  | 13 ++++++++++++-
 spec/components/discourse_redis_spec.rb | 26 +++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/lib/discourse.rb b/lib/discourse.rb
index aa417260daf..84175589723 100644
--- a/lib/discourse.rb
+++ b/lib/discourse.rb
@@ -489,7 +489,7 @@ module Discourse
   end
 
   def self.readonly_mode?(keys = READONLY_KEYS)
-    recently_readonly? || Discourse.redis.mget(*keys).compact.present?
+    recently_readonly? || Discourse.redis.exists(*keys)
   end
 
   def self.pg_readonly_mode?
diff --git a/lib/discourse_redis.rb b/lib/discourse_redis.rb
index 6b630b7b34d..5ef5de9ce9d 100644
--- a/lib/discourse_redis.rb
+++ b/lib/discourse_redis.rb
@@ -194,7 +194,7 @@ class DiscourseRedis
   end
 
   # Proxy key methods through, but prefix the keys with the namespace
-  [:append, :blpop, :brpop, :brpoplpush, :decr, :decrby, :exists, :expire, :expireat, :get, :getbit, :getrange, :getset,
+  [:append, :blpop, :brpop, :brpoplpush, :decr, :decrby, :expire, :expireat, :get, :getbit, :getrange, :getset,
    :hdel, :hexists, :hget, :hgetall, :hincrby, :hincrbyfloat, :hkeys, :hlen, :hmget, :hmset, :hset, :hsetnx, :hvals, :incr,
    :incrby, :incrbyfloat, :lindex, :linsert, :llen, :lpop, :lpush, :lpushx, :lrange, :lrem, :lset, :ltrim,
    :mapped_hmset, :mapped_hmget, :mapped_mget, :mapped_mset, :mapped_msetnx, :move, :mset,
@@ -208,6 +208,17 @@ class DiscourseRedis
     end
   end
 
+  # Remove when this has been upstreamed in https://github.com/redis/redis-rb/pull/911
+  def exists(*keys)
+    keys.map! { |a| "#{namespace}:#{a}" }  if @namespace
+
+    DiscourseRedis.ignore_readonly do
+      @redis._client.call([:exists, *keys]) do |value|
+        value > 0
+      end
+    end
+  end
+
   def mget(*args)
     args.map! { |a| "#{namespace}:#{a}" }  if @namespace
     DiscourseRedis.ignore_readonly { @redis.mget(*args) }
diff --git a/spec/components/discourse_redis_spec.rb b/spec/components/discourse_redis_spec.rb
index abc9a5917a8..059e1449628 100644
--- a/spec/components/discourse_redis_spec.rb
+++ b/spec/components/discourse_redis_spec.rb
@@ -87,6 +87,32 @@ describe DiscourseRedis do
         expect(Discourse.recently_readonly?).to eq(true)
       end
     end
+
+    # Remove when this has been upstreamed in https://github.com/redis/redis-rb/pull/911
+    describe '.exists' do
+      it 'should return false when key is not present' do
+        expect(Discourse.redis.exists('test')).to eq(false)
+      end
+
+      it 'should return false when keys are not present' do
+        expect(Discourse.redis.exists('test', 'test2')).to eq(false)
+      end
+
+      it 'should return true when key is present' do
+        Discourse.redis.set('test', 1)
+
+        expect(Discourse.redis.exists('test')).to eq(true)
+      end
+
+      it 'should return true when any key is present' do
+        Discourse.redis.set('test', 1)
+        Discourse.redis.set('test2', 1)
+
+        expect(Discourse.redis.exists('test')).to eq(true)
+        expect(Discourse.redis.exists('test', 'test2')).to eq(true)
+        expect(Discourse.redis.exists('test2', 'test3')).to eq(true)
+      end
+    end
   end
 
   context '.slave_host' do