FEATURE: Improve backup stats on admin dashboard

* Dashboard doesn't timeout anymore when Amazon S3 is used for backups
* Storage stats are now a proper report with the same caching rules
* Changing the backup_location, s3_backup_bucket or creating and deleting backups removes the report from the cache
* It shows the number of backups and the backup location
* It shows the used space for the correct backup location instead of always showing used space on local storage
* It shows the date of the last backup as relative date

spec/lib/backup_restore/s3_backup_store_spec.rb

@@ -81,11 +81,19 @@ describe BackupRestore::S3BackupStore do
     before { create_backups }
     after(:all) { remove_backups }
 
-    it "doesn't delete files when cleanup is disabled" do
-      SiteSetting.maximum_backups = 1
-      SiteSetting.s3_disable_cleanup = true
+    describe "#delete_old" do
+      it "doesn't delete files when cleanup is disabled" do
+        SiteSetting.maximum_backups = 1
+        SiteSetting.s3_disable_cleanup = true
 
-      expect { store.delete_old }.to_not change { store.files }
+        expect { store.delete_old }.to_not change { store.files }
+      end
+    end
+
+    describe "#stats" do
+      it "returns nil for 'free_bytes'" do
+        expect(store.stats[:free_bytes]).to be_nil
+      end
     end
   end
 

spec/lib/backup_restore/shared_examples_for_backup_store.rb

@@ -29,6 +29,17 @@ shared_examples "backup store" do
         expect(store.latest_file).to be_nil
       end
     end
+
+    describe "#stats" do
+      it "works when there are no files" do
+        stats = store.stats
+
+        expect(stats[:used_bytes]).to eq(0)
+        expect(stats).to have_key(:free_bytes)
+        expect(stats[:count]).to eq(0)
+        expect(stats[:last_backup_taken_at]).to be_nil
+      end
+    end
   end
 
   context "with backup files" do
@@ -69,6 +80,18 @@ shared_examples "backup store" do
       end
     end
 
+    describe "#reset_cache" do
+      it "resets the storage stats report" do
+        report_type = "storage_stats"
+        report = Report.find(report_type)
+        Report.cache(report, 35.minutes)
+        expect(Report.find_cached(report_type)).to be_present
+
+        store.reset_cache
+        expect(Report.find_cached(report_type)).to be_nil
+      end
+    end
+
     describe "#delete_old" do
       it "does nothing if the number of files is <= maximum_backups" do
         SiteSetting.maximum_backups = 3
@@ -166,6 +189,17 @@ shared_examples "backup store" do
         end
       end
     end
+
+    describe "#stats" do
+      it "returns the correct stats" do
+        stats = store.stats
+
+        expect(stats[:used_bytes]).to eq(57)
+        expect(stats).to have_key(:free_bytes)
+        expect(stats[:count]).to eq(3)
+        expect(stats[:last_backup_taken_at]).to eq(Time.parse("2018-09-13T15:10:00Z"))
+      end
+    end
   end
 end