PERF: Disable Sidekiq only during database restore (#10857)

It pauses Sidekiq, clears Redis (namespaced to the current site), clears Sidekiq jobs for the current site, restores the database and unpauses Sidekiq. Previously it stayed paused until the end of the restore.

Redis is cleared because we don't want any old data lying around (e.g. old Sidekiq jobs). Most data in Redis is prefixed with the name of the multisite, but Sidekiq jobs in a multisite are all stored in the same keys. So, deleting those jobs requires a little bit more logic.

spec/lib/backup_restore/system_interface_spec.rb

@@ -10,7 +10,7 @@ describe BackupRestore::SystemInterface do
 
   context "readonly mode" do
     after do
-      Discourse::READONLY_KEYS.each { |key| $redis.del(key) }
+      Discourse::READONLY_KEYS.each { |key| Discourse.redis.del(key) }
     end
 
     describe "#enable_readonly_mode" do
@@ -81,16 +81,23 @@ describe BackupRestore::SystemInterface do
   end
 
   describe "#pause_sidekiq" do
+    after { Sidekiq.unpause! }
+
     it "calls pause!" do
-      Sidekiq.expects(:pause!).once
-      subject.pause_sidekiq
+      expect(Sidekiq.paused?).to eq(false)
+      subject.pause_sidekiq("my reason")
+      expect(Sidekiq.paused?).to eq(true)
+      expect(Discourse.redis.get(SidekiqPauser::PAUSED_KEY)).to eq("my reason")
     end
   end
 
   describe "#unpause_sidekiq" do
     it "calls unpause!" do
-      Sidekiq.expects(:unpause!).once
+      Sidekiq.pause!
+      expect(Sidekiq.paused?).to eq(true)
+
       subject.unpause_sidekiq
+      expect(Sidekiq.paused?).to eq(false)
     end
   end
 
@@ -101,12 +108,16 @@ describe BackupRestore::SystemInterface do
     end
 
     context "with Sidekiq workers" do
-      before { $redis.flushall }
-      after { $redis.flushall }
+      before { flush_sidekiq_redis_namespace }
+      after { flush_sidekiq_redis_namespace }
+
+      def flush_sidekiq_redis_namespace
+        Sidekiq.redis do |redis|
+          redis.scan_each { |key| Discourse.redis.del(key) }
+        end
+      end
 
       def create_workers(site_id: nil, all_sites: false)
-        $redis.flushall
-
         payload = Sidekiq::Testing.fake! do
           data = { post_id: 1 }
 
@@ -157,5 +168,46 @@ describe BackupRestore::SystemInterface do
         subject.wait_for_sidekiq
       end
     end
+
+    describe "flush_redis" do
+      context "Sidekiq" do
+        after { Sidekiq.unpause! }
+
+        it "doesn't unpause Sidekiq" do
+          Sidekiq.pause!
+          subject.flush_redis
+
+          expect(Sidekiq.paused?).to eq(true)
+        end
+      end
+
+      it "removes only keys from the current site in a multisite", type: :multisite do
+        test_multisite_connection("default") do
+          Discourse.redis.set("foo", "default-foo")
+          Discourse.redis.set("bar", "default-bar")
+
+          expect(Discourse.redis.get("foo")).to eq("default-foo")
+          expect(Discourse.redis.get("bar")).to eq("default-bar")
+        end
+
+        test_multisite_connection("second") do
+          Discourse.redis.set("foo", "second-foo")
+          Discourse.redis.set("bar", "second-bar")
+
+          expect(Discourse.redis.get("foo")).to eq("second-foo")
+          expect(Discourse.redis.get("bar")).to eq("second-bar")
+
+          subject.flush_redis
+
+          expect(Discourse.redis.get("foo")).to be_nil
+          expect(Discourse.redis.get("bar")).to be_nil
+        end
+
+        test_multisite_connection("default") do
+          expect(Discourse.redis.get("foo")).to eq("default-foo")
+          expect(Discourse.redis.get("bar")).to eq("default-bar")
+        end
+      end
+    end
   end
 end