Server error 502 causes conflicts (reproducible) #3008

[64kramsystem]

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Expected behaviour

If the server sends a 502 (Bad gateway) because of issues, while the user is changing some files content, the desktop client should not generate any conflict when the client successfully connects again to the server.

Actual behaviour

What happens (I've reproduced this problem several times) is that when the client connects back to the server (say, because the server is online again), a conflict is generated, between the current version of the file, and the previous one.

I suppose that what's happening is that (speculation on my part):

• the client sends the file content
• the server receives it, but sends a 502 for any reason
• the client sends the updated file content, thinking it's the previous version
• now the server is online; now it will have two versions, and notifies the client of a conflict

Steps to reproduce

1. make the server send 502s to the client (I guess via overload)
2. edit the file
3. wait for the server to come back online
4. conflict!

Client configuration

Client version: 3.1.3 Operating system: Ubuntu OS language: Eglish Qt version used by client package (Linux only, see also Settings dialog): I can't find it in the settings, but the dependent package libqt5gui5 has version 5.12.8+dfsg-0ubuntu1. Client package (From Nextcloud or distro) (Linux only): nextcloud-desktop 3.1.3-20210218.151938.3842d306f-1.0~focal1. Installation path of client: /usr/bin/nextcloud

Server configuration

Nextcloud version:

Storage backend (external storage):

Logs

Logs extraction, anonymized: wrong_conflict_on_504.anon.zip

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[64kramsystem]

All the details provided are above.

[n-e-y-s]

Maybe the root cause is related to https://github.com/nextcloud/desktop/issues/2483

The client might take the 502 answer for the new content of the file and then the conflict while editing the file is justified. (The client should always check for any errors in server answers and prevent file corruption in any case.)

[64kramsystem]

Maybe the root cause is related to #2483

The client might take the 502 answer for the new content of the file and then the conflict while editing the file is justified. (The client should always check for any errors in server answers and prevent file corruption in any case.)

Thanks for following up, but I've long dumped Nextcloud. Maestral+Dropbox doesn't have such (serious) bugs. Autoclosing this issue has also been an extremely questionable practice.