Hi,
On 24.08.2018 18:18, Uoti Urpala wrote:
On Fri, 2018-08-24 at 14:52 +0300, David Weinehall wrote:
The second time-related issue pertains to journalctl.
It seems that journalctl logs (or at least displays) events in date/clock
order, not in
sequence order. While this is definitely useful when trying to correlate
different logs
against each other, it also means that events that happen after a date
adjustment might
end up before already existing entries, thus breaking the sequentialness of the
log,
as follows:
Date incorrect set to 2023:
Log message 1
Log message 2
Date corrected to be 2018:
Log message 3
Log message 1
Log message 2
Typically this is not how we want our log to behave. Is there any way to
show the log in sequential order?
Within one journal file, entries are stored in the order they are
received, and the normal tools like journalctl will also display events
from within the file in that order. Output like the above shouldn't be
the typical consequence of changing time during a single boot, as the
later entries should usually keep being written in the same file as the
previous ones. (It can happen, but your "reproduction steps" above are
likely incomplete as to what is actually required to see such effects).
Where you can see issues is between entries stored in separate journal
files. Those may not contain information that would allow comparing two
entries stored in the different files by anything other than the
unreliable realtime timestamp.
Shouldn't globally sequential ordering be one of the first requirements
for any log system?
Note that the journal display code has some fairly serious breakage in
the area of handling messages that may have unreliable timestamps,
which may cause issues such as some messages not being shown at all.
The commit message of the proposed patch in the message linked below is
probably the best writeup (no fixes have been applied to this area
AFAIK):
https://lists.freedesktop.org/archives/systemd-devel/2017-December/039976.html
The log messages could have disappeared, it's hard to say with
journal containing info about dozens of reboots with the same time
stamps (this is from an embedded device without battery backed clock,
where systemd daemon doesn't get time synced early enough from network
that log messages would have correct time stamps).
At least the latest messages logged were not at the end of the
journalctl output where they should have.
Regards,
- Eero
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