On 10/04/2014 05:55 AM, Aleksei Besogonov wrote:
With all the recent noise about systemd abusing its position with the
way it takes over logging I’ve been thinking about a way to solve it.
As far as I understand the following holds:
- Systemd takes over /dev/log socket which is normally served by
rsyslog (or other syslog daemon).
- That’s really required to make journald-based logging transparent
and coherent for most use-cases.
However, it creates a problem for log-heavy applications, because of
additional roundtrips between processes. So far I’ve heard people
actually using LD_PRELOAD tricks to hack around applications opening
the /dev/log file inside the syslog(2). As far as I understand, it’s
also not really configurable - the '/dev/log’ string is hardcoded into
various libcs (e.g.:
http://git.musl-libc.org/cgit/musl/tree/src/misc/syslog.c). Recent
versions of rsyslog can directly read journald files. But that’s still
suboptimal solution, because it introduces an unnecessary layer.
Namespacing each daemon to provide its own /dev tree with custom
/dev/log sockets is possible, but impractical.
So I propose the following solution:
1) Add an option to systemd units to allow passing opened /dev/log
sockets to rsyslog (using the usual SOL_SOCKET mechanism).
2) Add the corresponding functionality to rsyslog. It should listen on
a special socket (perhaps /run/rsyslog/socket_server ?) and treat all
the incoming sockets as if they were accepted from /dev/log.
It would also solve the problems with rsyslog using its own
SCM_CREDENTIALS lookups.
Tying the solution to rsyslog or syslog-ng is not something that should
be done but rather fix the usability.
Based on what I have observed thus far people uses of sending journal
logs to centralized syslog server of any kind boils down to...
"journalctl -o <format> -f | ncat <protocol><host><port>"
"journalctl -o <format> -f | <own written python tool/filter who then
sends the logs> <protocol><host><port>"
As well as adding somekind of token in front of the log entries (
cloud/container specific ) as in
"ncat --ssl --ssl-verify <host> <port> < <(awk -v token=token_here '{
print token, $0; fflush(); }' < <(journalctl -o short -f))"
Embedded uses netconsole as in
systemd.log_target=kmsg
netconsole=[src-port]@[src-ip]/[],[tgt-port]@/[tgt-macaddr]
So the solution which combines these common denominators thus should
eventually make everyone happy is integrate something like netconsole...
Then add following lines to journald.conf
ForwardToHost=yes
ForwardToHostIP=<Destination IP>
ForwardToHostPort=<Destination Port>
ForwardToHostFormat=<short,json etc >
ForwardToHostLogToken=<insert token who get appended before each log
line here probably should default to machineid>
If someone does provide patches that does just that or similar I think
this outspoken shortcoming of journal can be finally put to rest and
people be happy.
JBG
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