On Mon, 06.02.17 11:12, Florian Weimer (fwei...@redhat.com) wrote: > The manual page I've got does not say it is, but the implementation does not > wait for acknowledgment from the journal. The implementation does not block > explicitly, but I think the sendmsg call can block until the receiver queue > is empty. > > The background for this question is that we have a feature request for a > non-blocking logging interface. I wonder if the journal fits this > requirement. > > I assume that with “non-blocking”, the feature request submitter means that > the function does not block indefinitely, say due to a service process > outage. Memory allocations can take a fairly long time as well (due to > paging), but I think that doesn't count here.
The socket we use is blocking, but we try to increase the socket buffer to 8M, to move the point where we start to block out late. But that only works with sufficient privileges. So yes, we are always blocking, we don't throw data away. I'd be willing to take a patch however, that adds a call sd_journal_set_block_timeout() or so, that takes a time value we pass to SO_SNDTIMEO for the logging socket. This would permit clients to precisely control how long they want us to wait before we give up. And in the case where a zero timeout is set we'd instead set O_NONBLOCK, thus making logging entirely non-blocking. But of course, you can't have it both. Pick one of "don't lose messages" and "never block". Right now we always opt for the former, with such a function call you could give that up and opt for the latter. Lennart -- Lennart Poettering, Red Hat _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
