Silence errors when Azure objects have aleady been deleted

In an normal upload flow, GitLab Rails will move a file to its final
destination and remove the temporary file. Workhorse issues a DELETE a
request to ensure this is cleaned up. Previously this was generating log
noise with every upload. Now only log an error message if there were
some error other than a 404.

changelogs/unreleased/sh-silence-gocloud-404-deletions.yml

+---
+title: Silence errors when Azure objects have aleady been deleted
+merge_request: 585
+author:
+type: fixed

internal/objectstore/gocloud_object.go

@@ -7,6 +7,7 @@ import (
 
 	"gitlab.com/gitlab-org/labkit/log"
 	"gocloud.dev/blob"
+	"gocloud.dev/gcerrors"
 )
 
 type GoCloudObject struct {
@@ -95,6 +96,8 @@ func (o *GoCloudObject) Delete() {
 	}
 
 	if err := bucket.Delete(deleteCtx, o.objectName); err != nil {
-		log.WithError(err).Error("error deleting object", err)
+		if gcerrors.Code(err) != gcerrors.NotFound {
+			log.WithError(err).Error("error deleting object")
+		}
 	}
 }

internal/objectstore/gocloud_object_test.go

@@ -12,9 +12,12 @@ import (
 
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/objectstore"
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/objectstore/test"
+	"gitlab.com/gitlab-org/gitlab-workhorse/internal/testhelper"
 )
 
 func TestGoCloudObjectUpload(t *testing.T) {
+	logHook := testhelper.SetupLogger()
+
 	mux, _, cleanup := test.SetupGoCloudFileBucket(t, "azuretest")
 	defer cleanup()
 
@@ -61,4 +64,9 @@ func TestGoCloudObjectUpload(t *testing.T) {
 	})
 
 	require.True(t, deleted)
+
+	// Verify no log noise when deleting a file that already is gone
+	object.Delete()
+	entries := logHook.AllEntries()
+	require.Equal(t, 0, len(entries))
 }