Golang: syscall.WriteMsgUnix breaks large journal

[philips]

This is a tracking issue for the upstream Golang bug that keeps the large journal entry stuff from working right now. Large journal entries won't work until this is fixed upstream in Golang:

https://code.google.com/p/go/issues/detail?id=6476

[aletheia7]

According to the bug report, a patch was created and a test of sending 4MB was used to confirm the fix. Apparently this is a limitiation of the systemd-journald.socket interface.

Another way to write to the systemd journal is using sd_journal_sendv(). I created a go package entitled sd. I use the sd_journal_sendv() interface and had no problem sending 40MB. The sd.Journal.Send() method in journal.go provides an example of using send_journal_sendv(). Hope this helps.

Thanks for sharing the go-systemd package.

[bcwaldon]

upstream bug still not fixed, moved to golang/go#6476

[mildred]

Apparently this is going to be fixed in go 1.10 at worst : https://go-review.googlesource.com/c/go/+/45872

[mildred]

Is it possible to clarify which API are affected? Will using the sdjournal package, especially the functions on sdjournal.Journal can cause problems?

I am asking because I have an issue with journalbeat which uses go-systemd. Recently, logs got corrupted, and I was indeed having very large journal files that were being rotated by journald.

edit: I'm being silly, the sdjournal package is reading the journal from disk and is not using the unix datagram socket.

[lucab]

@mildred yes, I'm waiting for 1.9 to rebase and then cherry-pick to x/sys as well. But I don't think this bug is related in any way to what you are seeing, it only affects clients trying to send large entries (send will fail).

[lucab]

Good news is that my fix is now released as part of Go 1.10. Bad news is that after backporting to x/sys I realized we can't really start using it right now.

I will wait for the next Go release (1.11) before starting to use it, thus closing this ticket at that point. Until then, this still blocks #218 (comment).