Hacktoberfest 2026: the issues maintainers tagged for October, open and beginner-friendly. Browse Hacktoberfest issues

lmLog: "Server error occured" when log contains non-ASCII chars (offset counted in chars, seek in bytes)

Open
  • Is something wrong?
#294 0 comments 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
78/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
javascript, python
Domain
backend, frontend

Research direction

Start in lmn_common/views.py at handle_api_log, which seeks by offset, and in lmn_common/resources/js/directives/lmlog.coffee, which sends offset=$scope.content.length. Decide on byte offsets end-to-end (binary read plus a response header the CoffeeScript client uses for the next offset) or the fallback errors='replace'. Reproduce with the two-line Python snippet from the issue, then verify the log view polls past an umlaut-heavy file without a 500.

Written by the indexing model from the issue text.

Description

Description

While users are applied in List Management, the live log view polls
GET /api/lmn/log/tmp/sophomorix.log?offset=<n> every second. Sporadically
the WebUI shows "Server error occured. This is likely a bug." for this request.
The sophomorix run itself completes; only the log view breaks.

Cause

Frontend and backend use different units for offset:

  • lmn_common/resources/js/directives/lmlog.coffee sends
    offset=#{$scope.content.length}, which is the length in characters (JS string).
  • lmn_common/views.py → handle_api_log opens the file in text mode and calls
    f.seek(offset), which positions by bytes.

Each non-ASCII character (ä, ö, ü, ß in user names, ...) is 1 char but 2 bytes in
UTF-8, so the offset drifts by one byte per umlaut. When it lands inside a
multibyte sequence, f.read() raises UnicodeDecodeError and the endpoint returns 500.

Minimal reproduction:

open('t.log','w').write('Benutzer Müller angelegt\n')
f = open('t.log'); f.seek(11); f.read()
# UnicodeDecodeError: 'utf-8' codec can't decode byte 0xbc in position 0

With multi-school setups the log easily grows to >1 MB with many umlauts
(we saw offset=1682314), so the error shows up on almost every run.

Environment

linuxmuster-webui7 7.3.40; code is unchanged on master / 7.3.46.

Possible fix

Use byte offsets consistently, e.g. read the file in binary mode and let the
frontend track the received byte length (e.g. via a response header), or at least
open(path, errors='replace') so a misaligned offset no longer causes a 500.

Dominant language
HTML
Stars
14
Forks
9
No merged PRs in 30d

Getting set up

This project ships no dev container, Dockerfile or contributing guide, so setting up is up to you: start from its README, and see our first-contribution guide for the general steps.

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from linuxmuster/linuxmuster-webui7

All issues in linuxmuster/linuxmuster-webui7

Similar issues

More Backend & API Design issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.