mirror of
https://github.com/ceph/ceph
synced 2024-12-15 16:07:00 +00:00
107 lines
4.7 KiB
ReStructuredText
107 lines
4.7 KiB
ReStructuredText
|
|
Use of the cluster log
|
|
======================
|
|
|
|
(Note: none of this applies to the local "dout" logging. This is about
|
|
the cluster log that we send through the mon daemons)
|
|
|
|
Severity
|
|
--------
|
|
|
|
Use ERR for situations where the cluster cannot do its job for some reason.
|
|
For example: we tried to do a write, but it returned an error, or we tried
|
|
to read something, but it's corrupt so we can't, or we scrubbed a PG but
|
|
the data was inconsistent so we can't recover.
|
|
|
|
Use WRN for incidents that the cluster can handle, but have some abnormal/negative
|
|
aspect, such as a temporary degredation of service, or an unexpected internal
|
|
value. For example, a metadata error that can be auto-fixed, or a slow operation.
|
|
|
|
Use INFO for ordinary cluster operations that do not indicate a fault in
|
|
Ceph. It is especially important that INFO level messages are clearly
|
|
worded and do not cause confusion or alarm.
|
|
|
|
Frequency
|
|
---------
|
|
|
|
It is important that messages of all severities are not excessively
|
|
frequent. Consumers may be using a rotating log buffer that contains
|
|
messages of all severities, so even DEBUG messages could interfere
|
|
with proper display of the latest INFO messages if the DEBUG messages
|
|
are too frequent.
|
|
|
|
Remember that if you have a bad state (as opposed to event), that is
|
|
what health checks are for -- do not spam the cluster log to indicate
|
|
a continuing unhealthy state.
|
|
|
|
Do not emit cluster log messages for events that scale with
|
|
the number of clients or level of activity on the system, or for
|
|
events that occur regularly in normal operation. For example, it
|
|
would be inappropriate to emit a INFO message about every
|
|
new client that connects (scales with #clients), or to emit and INFO
|
|
message about every CephFS subtree migration (occurs regularly).
|
|
|
|
Language and formatting
|
|
-----------------------
|
|
|
|
(Note: these guidelines matter much less for DEBUG-level messages than
|
|
for INFO and above. Concentrate your efforts on making INFO/WRN/ERR
|
|
messages as readable as possible.)
|
|
|
|
Use the passive voice. For example, use "Object xyz could not be read", rather
|
|
than "I could not read the object xyz".
|
|
|
|
Print long/big identifiers, such as inode numbers, as hex, prefixed
|
|
with an 0x so that the user can tell it is hex. We do this because
|
|
the 0x makes it unambiguous (no equivalent for decimal), and because
|
|
the hex form is more likely to fit on the screen.
|
|
|
|
Print size quantities as a human readable MB/GB/etc, including the unit
|
|
at the end of the number. Exception: if you are specifying an offset,
|
|
where precision is essential to the meaning, then you can specify
|
|
the value in bytes (but print it as hex).
|
|
|
|
Make a good faith effort to fit your message on a single line. It does
|
|
not have to be guaranteed, but it should at least usually be
|
|
the case. That means, generally, no printing of lists unless there
|
|
are only a few items in the list.
|
|
|
|
Use nouns that are meaningful to the user, and defined in the
|
|
documentation. Common acronyms are OK -- don't waste screen space
|
|
typing "Rados Object Gateway" instead of RGW. Do not use internal
|
|
class names like "MDCache" or "Objecter". It is okay to mention
|
|
internal structures if they are the direct subject of the message,
|
|
for example in a corruption, but use plain english.
|
|
Example: instead of "Objecter requests" say "OSD client requests"
|
|
Example: it is okay to mention internal structure in the context
|
|
of "Corrupt session table" (but don't say "Corrupt SessionTable")
|
|
|
|
Where possible, describe the consequence for system availability, rather
|
|
than only describing the underlying state. For example, rather than
|
|
saying "MDS myfs.0 is replaying", say that "myfs is degraded, waiting
|
|
for myfs.0 to finish starting".
|
|
|
|
While common acronyms are fine, don't randomly truncate words. It's not
|
|
"dir ino", it's "directory inode".
|
|
|
|
If you're logging something that "should never happen", i.e. a situation
|
|
where it would be an assertion, but we're helpfully not crashing, then
|
|
make that clear in the language -- this is probably not a situation
|
|
that the user can remediate themselves.
|
|
|
|
Avoid UNIX/programmer jargon. Instead of "errno", just say "error" (or
|
|
preferably give something more descriptive than the number!)
|
|
|
|
Do not mention cluster map epochs unless they are essential to
|
|
the meaning of the message. For example, "OSDMap epoch 123 is corrupt"
|
|
would be okay (the epoch is the point of the message), but saying "OSD
|
|
123 is down in OSDMap epoch 456" would not be (the osdmap and epoch
|
|
concepts are an implementation detail, the down-ness of the OSD
|
|
is the real message). Feel free to send additional detail to
|
|
the daemon's local log (via `dout`/`derr`).
|
|
|
|
If you log a problem that may go away in the future, make sure you
|
|
also log when it goes away. Whatever priority you logged the original
|
|
message at, log the "going away" message at INFO.
|
|
|