Sync client gets into loop with RECONFIGURATION or NEWLY_SUPPORTED_DATATYPE

[urbenlegend]

Description

I tried adding a new device to my sync chain. It managed to sync my bookmarks, but when I enable the option to "Sync everything", it now no longer works properly. My extensions are never synced and brave://sync-internals is spamming a bunch of RECONFIGURATION messages:

The sync chain is also relatively new (2 weeks old). It isn't some old sync chain from back in the day that had sync issues.

Steps to Reproduce

1. Add a new device to an existing sync chain
2. Go into sync settings and enable "Sync everything"
3. Notice that nothing else is properly synced and that brave://sync-internals is spamming the same RECONFIGURATION messages over and over again

Actual result:

Nothing except bookmarks can be synced. Enabling "Sync everything" makes sync go into an infinite loop of RECONFIGURATION messages

Expected result:

Everything is properly synced.

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

1.65.126 Chromium: 124.0.6367.118 (Official Build) (64-bit)

Version/Channel Information:

• Can you reproduce this issue with the current release? Yes
• Can you reproduce this issue with the beta channel? Not tested
• Can you reproduce this issue with the nightly channel? Not tested

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? No
• Does the issue resolve itself when disabling Brave Rewards? No
• Is the issue reproducible on the latest version of Chrome? N/A

Miscellaneous Information:

[urbenlegend]

Turning off history sync and then restarting the entire browser seems to stop the infinite loop and allow syncing of the other categories. Re-enabling it again immediately causes the issue.

Seems like something borked with history sync.

My existing devices that were paired before are able to sync history though. It is only with newly paired devices that this issue occurs.

[urbenlegend]

I ended up deleting the entire sync chain and just recreating a brand new one. Not sure what was borked with the previous one but this should be fixed to prevent confusion for other users.

[rebron]

cc: @AlexeyBarabash

[AlexeyBarabash]

@urbenlegend thank you for report

we are working on the sync server fix , the best for now to disable history sync, till we not deploy the fix.

[bsclifton]

I ran into this one myself - @AlexeyBarabash tried to reproduce, but wasn't able to.

Here are the steps I did:

1. Got myself into a broken state (basically same symptoms as Sync chain randomly ceases working #35042)
2. Turned off history sync
3. Continued to use the product for a while (2 hours?)
4. Turn back ON history sync
5. Waited ~10 minutes - new sync happened (saw it happen on brave://sync-internals)
6. Went to brave://sync-internals and saw traffic logs exploding with RECONFIGURATION
7. Closed browser, waited a few mins
8. Opened browser
9. Went to brave://sync-internals and saw traffic logs exploding with NEWLY_SUPPORTED_DATATYPE

Here is some screenshots from when I hit the first error. You can see how fast it's going.

And here's a static screenshot of the second one. It was spamming the server with transactions too- I just didn't get an animated pic.