As proposed in #8857, this adds a Logger subclass that writes structured
log messages via journald's native protocol by calling sd_journal_sendv.
The feature therefore depends on the systemd library. sd_journal_sendv is
available since the early days (systemd v38), so a version check is
probably superflous.
We add the following fields to each record:
- MESSAGE: The log message
- PRIORITY (aka severity): Numeric severity as in RFC5424 section 6.2.1
- SYSLOG_FACILITY: Numeric facility as in RFC5424 section 6.2.1
- SYSLOG_IDENTIFIER: If provided, use value from configuration.
Else use systemd's default behaior, which is to determine the field
by using libc's program_invocation_short_name, resulting in "icinga2".
- ICINGA2_FACILITY: Facility as in Log::Log(..., String facility, ...),
e.g. "ApiListener"
- some more fields are added automatically by systemd
Fields are stored indexed, so we can do fast queries for certain field
values. Example:
$ journalctl -t icinga2 ICINGA2_FACILITY=ApiListener -n 5
Syslog compatiblity is ratained because good old tag, severity and facility
is stored along, and systemd can forward to syslog daemons.
See also https://systemd.io/JOURNAL_NATIVE_PROTOCOL/.
Tobias Deiminger