Bug 488434

Summary:	Quite much "kf.kio.core: An error occurred during write" output in syslog
Product:	[Applications] dolphin	Reporter:	nttkde <watisthispoo>
Component:	general	Assignee:	Dolphin Bug Assignee <dolphin-bugs-null>
Status:	CONFIRMED ---
Severity:	normal	CC:	4wy78uwh, dolphin-bugs-null, meven29
Priority:	NOR
Version First Reported In:	24.05.0
Target Milestone:	---
Platform:	Other
OS:	Linux
See Also:	https://bugs.kde.org/show_bug.cgi?id=486697
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description nttkde 2024-06-12 23:04:48 UTC

Filing this bug initially to Dolphin as it seems to be triggering it (I haven't at least yet noticed other apps causing it but it's possible) but feel free to move to kio if it's definitely not a Dolphin bug.


kioworker[324665]: kf.kio.core: An error occurred during write. The worker terminates now.

At least opening a new tab or refreshing a folder rapidly may cause the line appear in syslog.
There aren't any other side effects that I'd have noticed.


I believe this regression started with Plasma 6 release, I didn't spot it in Plasma 5.

Operating System: KDE neon 6.0
KDE Plasma Version: 6.0.5
KDE Frameworks Version: 6.2.0
Qt Version: 6.7.0
Kernel Version: 5.15.0-112-generic (64-bit)
Graphics Platform: Wayland

As the error message is quite nondescript, let me know if I could somehow further debug its source.

Comment 1 nttkde 2024-08-23 19:11:35 UTC

Looks like the error is printed from from SlaveBase::send() in frameworks/kio/src/core/slavebase.cpp.
Printing cmd and arr when the error is printed seem to every time have values cmd: 102 and arr seems to contain string "Cannot create thumbnail for directory".

Comment 2 nttkde 2024-08-23 22:15:29 UTC

Looking a bit more carefully into the source of the error, SlaveBase::send seems to call 
-> Connection::send() [kio/src/core/connection.cpp] -> Connection::sendnow() -> ConnectionBackend::sendCommand() [kio/src/core/connectionbackend.cpp]
which then sometimes returns false with socket->state() being QLocalSocket::UnconnectedState.

And newer Dolphin/KIO now logs a PeerClosedError right before the 'write' error:
kioworker[329483]: kf.kio.core.connection: Socket not connected QLocalSocket::PeerClosedError
kioworker[329483]: kf.kio.core: An error occurred during write. The worker terminates now.

Comment 3 Méven Car 2025-02-12 08:28:57 UTC

This issue is most common with the thumbnail:/ kioworker.
Since it can be a slow worker, it has a tendency to be interrupted abruptly when refreshing a directory for instance.
Those warnings points out this could be handled gracefully instead of having outside of expectation result devs should be wary of (what warnings are for).

Comment 4 Roke Julian Lockhart Beedell 2025-10-24 18:25:50 UTC

(In reply to nttkde from comment #2)

> And newer Dolphin/KIO now logs a PeerClosedError right before the 'write'
> error:

If of any use, https://forum.qt.io/post/664235 provides some insight into the cause.

Comment 5 Bug Janitor Service 2025-10-25 09:32:47 UTC

A possibly relevant merge request was started @ https://invent.kde.org/frameworks/kio/-/merge_requests/2035