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Everything this process writes to stdout reaches the journal as PRIORITY=6,
whatever the Python level was, because journald has nothing else to go on.
Measured on a live rig over 24 hours:
lines containing " - ERROR - " 55
lines containing " - WARNING - " 13
journald PRIORITY recorded 6, for every one of them
So `journalctl -p err -u ledmatrix` returns nothing while errors are being
logged, and `-p warning` likewise. Triage falls back to grepping message text,
which is slower and unreliable: during this audit a search for "oom" matched
the radar logging "zoom=9" twenty-four times and briefly looked like the OOM
killer had been firing.
systemd reads a leading "<N>" on each stdout line and takes it as the priority
(sd-daemon(3)), so a formatter that prefixes one costs no dependency. Every
line of a multi-line record is tagged, not just the first -- the journal splits
them, and an untagged continuation reverts to the default, which would leave
the body of a traceback filed as informational while its first line was an
error.
Applied only when JOURNAL_STREAM is set, which systemd sets for services whose
output it captures. Run from a terminal, in the emulator or under pytest the
prefixes would be literal noise, and the file handler keeps the plain
formatter for the same reason.
Mutation-checked three ways: prefixing unconditionally fails the
outside-systemd test, prefixing only the first line fails the multi-line test,
and mapping ERROR to 6 fails the level mapping. 39 tests pass across the
logging suites.
(cherry picked from commit 780fca6365)
102 lines
3.8 KiB
Python
102 lines
3.8 KiB
Python
"""Log lines must reach the journal with their real severity.
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Everything this process writes to stdout lands in the journal as PRIORITY=6,
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whatever the Python level was, because journald has no other signal. Measured
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on a live rig over 24 hours: 55 lines containing " - ERROR - " and 13
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containing " - WARNING - ", every one of them recorded as informational. So
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journalctl -p err -u ledmatrix
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returned nothing while errors were being logged, and anyone triaging has to
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grep the message text instead. That is slower and it is wrong: a search for
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"oom" also matches the radar logging "zoom=9", which is exactly the false
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positive it produced during this audit.
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systemd reads a leading "<N>" on each stdout line and uses it as the priority
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(sd-daemon(3)), so this needs no extra dependency -- and it must only be
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applied when systemd is actually reading, or the prefixes become literal noise
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in a terminal, the emulator, and test output.
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"""
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import logging
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import os
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from unittest.mock import patch
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import pytest
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from src.logging_config import JournalPriorityFormatter, _SYSLOG_PRIORITY, _under_systemd
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class _Plain(logging.Formatter):
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def format(self, record):
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return record.getMessage()
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def _record(level, msg="hello"):
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return logging.LogRecord("t", level, "f.py", 1, msg, None, None)
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@pytest.mark.parametrize("level,expected", [
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(logging.CRITICAL, 2),
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(logging.ERROR, 3),
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(logging.WARNING, 4),
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(logging.INFO, 6),
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(logging.DEBUG, 7),
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])
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def test_each_level_maps_to_its_syslog_priority(level, expected):
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out = JournalPriorityFormatter(_Plain()).format(_record(level))
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assert out.startswith(f"<{expected}>"), out
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assert _SYSLOG_PRIORITY[level] == expected
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def test_error_and_info_are_distinguishable():
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"""The whole point: journalctl -p err must be able to tell them apart."""
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fmt = JournalPriorityFormatter(_Plain())
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assert fmt.format(_record(logging.ERROR))[:3] != fmt.format(_record(logging.INFO))[:3]
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def test_every_line_of_a_multiline_record_is_tagged():
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"""The journal splits them, and an untagged continuation loses its level.
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A traceback is the case that matters -- it is the most important thing in
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the log and the longest.
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"""
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out = JournalPriorityFormatter(_Plain()).format(
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_record(logging.ERROR, "Traceback:\nline one\nline two"))
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lines = out.split("\n")
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assert len(lines) == 3
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assert all(line.startswith("<3>") for line in lines), lines
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def test_the_message_survives_intact():
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out = JournalPriorityFormatter(_Plain()).format(_record(logging.WARNING, "disk full"))
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assert out == "<4>disk full"
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def test_an_unknown_level_falls_back_to_info():
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out = JournalPriorityFormatter(_Plain()).format(_record(25))
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assert out.startswith("<6>")
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def test_prefixing_is_off_outside_systemd():
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"""Otherwise a terminal run, the emulator and pytest all show `<6>`."""
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with patch.dict(os.environ, {}, clear=True):
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assert not _under_systemd()
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with patch.dict(os.environ, {"JOURNAL_STREAM": "8:12345"}):
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assert _under_systemd()
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def test_setup_uses_the_wrapper_only_under_systemd():
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from src.logging_config import setup_logging
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for env, expect_wrapped in (({}, False), ({"JOURNAL_STREAM": "8:1"}, True)):
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with patch.dict(os.environ, env, clear=True):
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setup_logging()
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handlers = [h for h in logging.getLogger().handlers
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if isinstance(h, logging.StreamHandler)]
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assert handlers, "no stream handler installed"
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wrapped = any(isinstance(h.formatter, JournalPriorityFormatter)
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for h in handlers)
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assert wrapped is expect_wrapped, (
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f"JOURNAL_STREAM={env}: wrapped={wrapped}, expected {expect_wrapped}")
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logging.getLogger().handlers.clear()
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