journalctl --sync should guarantee all currently in flight logs are written to the journal about systemd

[poettering]

hmm what's wrong with the existing journalctl --sync? what am i missing?

[DaanDeMeyer]

@poettering AFAIK that doesn't seem to do anything with logs that haven't been read from the service's file descriptor(s) yet? If I call journalctl --sync before journald reads the logs from the unit's file descriptor (or /run/systemd/journal/socket), then journalctl --sync doesn't actually guarantee those logs will be written to the journal?

If I currently do something like this

systemctl start oneshot-unit-that-logs-to-journal
journalctl --sync
journalctl --grep "log-message-from-oneshot-unit-that-logs-to-journal"

The journalctl grep might return an entry, or it might not return any entries at all. What I want is a way to ensure that that call to journalctl --grep will contain the logs from the oneshot service.

[poettering]

hmm, the idea was that the --sync stuff does exactly what you are looking for here, i.e. it only returns once every stream was fully processed.

[yuwata]

Yeah, currently journalctl --sync does not check stream, and there may be some pending data.

[yuwata]

-> #32617.