1331124 - Syncing large amount of bookmarks takes forever

Status: NEW

(Firefox :: Sync, defect, P3)

Description

[Kanchan Kumari QA]

STR:
1.Create a fresh profile and add large number of bookmarks to it (i.e. 10000 bookmarks)
2.Create a Firefox account and sign-in to Sync
3.Wait for sync to be done
4.In About Sync, verify that there are no validation errors
5.Sign in to second device with same Fx account

Expected: All bookmarks sync to second device 

Actual: Sync icon keeps spinning and sync doesn't happen(waited ~2h on my system)
In about:sync, Validation section just show message "The server records appear on the server but not on the client", but there are no records to show, just empty section

Comment 1

[Kanchan Kumari QA]

Attachment: ValidationError.json

Comment 2

[Kanchan Kumari QA]

Attachment: error-sync-1484349141806.txt

Comment 3

[Kanchan Kumari QA]

I retested this issue with several variations on two different hardware specs. Following are my observations: 

Please note that the bookmarks were initially synced to the server using latest nightly Fx 53.

1. This defect was seen on a laptop with following specs, while syncing bookmarks from server onto Fx nightly 52:
Intel Core i3-4005U CPU @ 1.70GHz 
RAM: 8GB (Win 10 x64)

2. It takes approx 1.5 hrs to 2.0 hrs for syncing ~10 k bookmarks to client from server on Fx nightly 53 with about sync add-on installed (trace enabled) with above specs. No validation errors seen.

3. Without about sync add-on it takes approx 25-30 minutes for syncing to complete with above specs on Fx 53 nightly.

4. On higher end machine with following specs it takes 6-10 minutes with about sync add-on (trace enabled) on Fx 53 Nightly. No validation errors seen.
   Intel Core i7-4810MQ CPU @ 2.80GHz
   RAM: 16 GB (Win 7 x64)

Comment 4

[Lina Butler (ex-Mozilla)]

That JSON export is all sorts of fun...it takes about 10-15 seconds for About Sync to process it on my machine, and I see a ton of records under "The following server records appear on the server but not on the client". I guess that's not surprising, if the sync didn't finish, but it's still unfortunate.

Bug 1305563 might help. It won't make downloading and decrypting any faster, but at least the bookmarks won't show up in the UI until they're all downloaded. That will make it less likely for folks to confuse Sync by moving those partially downloaded bookmarks around.

Comment 5

[Lina Butler (ex-Mozilla)]

A good first step is to profile this code, and see if there are any obvious improvements. It's also possible the add-on is slowing this down, per comment 3, step 3.