really fix disconnect_if_idle for Redis cluster

Cluster's internal structure of Redis clients is quite different,
so we can't just throw disconnect_if_idle on there

fixes AE-751

Change-Id: Ie967460078061dbf3754210f40fa6bd189bf26da
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/340996
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Isaac Moore <isaac.moore@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>

gems/canvas_cache/lib/canvas_cache/redis.rb

@@ -49,6 +49,12 @@ module CanvasCache
       end
     end
 
+    module Cluster
+      def disconnect_if_idle(since_when)
+        @router.instance_variable_get(:@node).clients.each { |c| c.disconnect_if_idle(since_when) }
+      end
+    end
+
     module IgnorePipelinedKey
       def pipelined(_key = nil, **kwargs, &)
         # ignore key; only useful for distributed
@@ -159,7 +165,8 @@ module CanvasCache
         ::Redis::Scripting::Module.prepend(Scripting::Module) if defined?(::Redis::Scripting::Module)
         ::Redis.prepend(Redis)
         ::Redis.prepend(IgnorePipelinedKey)
-        ::RedisClient::Cluster.prepend(Client)
+        ::RedisClient.prepend(Client)
+        ::Redis::Cluster::Client.prepend(Cluster)
         ::RedisClient::Cluster.prepend(IgnorePipelinedKey)
         ::Redis::Client.prepend(Client)
         ::Redis::Distributed.prepend(Distributed)

gems/canvas_cache/spec/canvas_cache/redis_spec.rb

@@ -18,6 +18,7 @@
 # with this program. If not, see <http://www.gnu.org/licenses/>.
 #
 
+require "redis/cluster"
 require "spec_helper"
 require "timecop"
 
@@ -310,22 +311,49 @@ describe CanvasCache::Redis do
   describe "#disconnect_if_idle" do
     let(:redis) { CanvasCache::Redis.redis }
     let(:client) { redis._client }
+    let(:raw_client) { client }
 
-    it "closes the connection if no command was ever received" do
-      expect(client).to receive(:close)
-      client.disconnect_if_idle(Process.clock_gettime(Process::CLOCK_MONOTONIC))
+    shared_examples "disconnect_if_idle" do
+      it "closes the connection if no command was ever received" do
+        expect(raw_client).to receive(:close)
+        client.disconnect_if_idle(Process.clock_gettime(Process::CLOCK_MONOTONIC))
+      end
+
+      it "does not close the connection if a commmand was recently received" do
+        redis.get("key")
+        expect(raw_client).not_to receive(:close)
+        client.disconnect_if_idle(Process.clock_gettime(Process::CLOCK_MONOTONIC) - 10)
+      end
+
+      it "closes the connection if a commmand was received, but not recently" do
+        redis.get("key")
+        expect(raw_client).to receive(:close)
+        client.disconnect_if_idle(Process.clock_gettime(Process::CLOCK_MONOTONIC) + 10)
+      end
     end
 
-    it "does not close the connection if a commmand was recently received" do
-      redis.get("key")
-      expect(client).not_to receive(:close)
-      client.disconnect_if_idle(Process.clock_gettime(Process::CLOCK_MONOTONIC) - 10)
-    end
+    include_examples "disconnect_if_idle"
 
-    it "closes the connection if a commmand was received, but not recently" do
-      redis.get("key")
-      expect(client).to receive(:close)
-      client.disconnect_if_idle(Process.clock_gettime(Process::CLOCK_MONOTONIC) + 10)
+    context "with a cluster" do
+      let(:redis) do
+        allow_any_instance_of(RedisClient::Cluster::Node).to receive(:refetch_node_info_list).and_return(
+          [RedisClient::Cluster::Node::Info.new(
+            id: "id",
+            node_key: "#{CanvasCache::Redis.redis._client.host}:#{CanvasCache::Redis.redis._client.port}",
+            role: "master",
+            primary_id: "-",
+            slots: [[0, 16_383]]
+          )]
+        )
+        Redis::Cluster.new(nodes: [CanvasCache::Redis.redis.id], connect_with_original_config: true)
+      end
+
+      let(:raw_client) do
+        router = client.instance_variable_get(:@router)
+        router.find_node(router.find_node_key(""))
+      end
+
+      include_examples "disconnect_if_idle"
     end
   end
 end