[Bug]: Linux desktop after v3.14.1 taking 100% CPU on multiple clients

[cpence]

⚠️ Before submitting, please verify the following: ⚠️

• This is a bug, not a question or a configuration issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server and Desktop Client are up to date. See Server Maintenance and Release Schedule and Desktop Releases for supported versions.
• I agree to follow Nextcloud's Code of Conduct

Bug description

Recent versions of the Linux desktop, later than 3.14.1, peg my CPU at 100% while syncing. The only thing that I could think of that makes my configuration special is that I have several group folders (using the extension).

Steps to reproduce

1. Update to any version >3.14.1 (I've tried on several 3.15s as Arch Linux has deployed the updates).
2. Synchronize, which completes just fine (green checkmark in the notification icon, etc.).
3. Observe nextcloud pegged at 100% CPU usage.

Expected behavior

The sync should take less than 100% CPU.

Which files are affected by this bug

unknown

Operating system

Linux

Which version of the operating system you are running.

Arch latest

Package

Distro package manager

Nextcloud Server version

30.0.4

Nextcloud Desktop Client version

3.15.3 (most recent tested w/ bug)

Is this bug present after an update or on a fresh install?

Updated to a major version (ex. 3.3.6 to 3.4.0)

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

Are you using an external user-backend?

• Default internal user-backend
• LDAP/ Active Directory
• SSO - SAML
• Other

Nextcloud Server logs

Additional info

No response

[cpence]

The debug log is 800+MB, is there a way for me to trim it before uploading, or should I just send the whole thing?

A few other things that might be worth noting:

• I see the same behavior on two identically configured computers
• The synced folder contains ~222,000 files
• With every sync, the client seems to write around 15MB of logs; my log directory is now up to 952M (i.e., in 10 minutes it's created ~100MB of logs)

[jothelander]

I am experiencing the same issue on Ubuntu 22.04 LTS with the latest AppImage version of the Nextcloud client (version 3.15.3).

Details:

• System specs: 32 GB RAM, Intel i7 CPU, 8 GB swap file.
• Additional setup: I am using Group Folders in my Nextcloud environment.

Issue description:

• The problem occurs immediately upon startup, with the AppRun process using 100% CPU.
• The client becomes unresponsive ("Nextcloud is not responding") for an extended period. After some time, it seems to recover, but interacting with the client (e.g., opening the UI) causes it to freeze again.

Server information:

• Provider: Managed Nextcloud from IONOS.
• Operating system: Linux 5.15.0-122-generic x86_64.
• Server CPU: Intel Xeon Processor (Skylake, IBRS) with 8 cores.
• Server memory: 62.76 GB RAM.

What I’ve tried:

• Tested both the AppImage version and the version installed via apt; the issue persists in both cases.
• Cleared configuration files (~/.config/Nextcloud, ~/.local/share/Nextcloud) and cache (~/.cache/Nextcloud).
• Adjusted system settings, including reducing swappiness to 20.
• Updated all system packages to the latest versions.

Additional context:

• I have been experiencing this issue for several client versions, but I am unsure exactly when it began.
• Logs do not show any unusual errors, and the server connection seems stable.
• The problem appears to involve periods of heavy resource usage (100% CPU) and UI responsiveness issues during synchronization or other interactions.

Please let me know if I can provide any additional logs, debugging output, or other details to assist in resolving this issue!

[cpence]

I get exactly the same UI unresponsiveness problems when the bug occurs as @jothelander, and I've also tried wiping configuration and caches, which didn't change anything.

[alraban]

I'm seeing the exact same issue (100% CPU after sync and unresponsive UI) on every client version after 3.14.1 on Arch Linux as well.