This fix tries to add an additional syslog-format of `rfc5424micro` which follows
the same as rfc5424 except that it use microsecond resolution for timestamp. The
purpose is to solve the issue raised in #21793 where log events might lose its
ordering if happens on the same second.
The timestamp field in rfc5424 is derived from rfc3339, though the maximium
resolution is limited to "TIME-SECFRAC" which is 6 (microsecond resolution).
The appropriate documentation (`docs/admin/logging/overview.md`) has been updated
to reflect the change in this fix.
This fix adds a unit test to cover the newly introduced format.
This fix fixes#21793.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
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