martin at meltin.net
Mon Dec 5 20:14:21 UTC 2016
On Mon, 28 Nov 2016 10:47:27 +0100, Andreas Schneider <asn at samba.org>
> On Monday, 28 November 2016 15:08:50 CET Martin Schwenke wrote:
> > Amitay and I are in the process of moving to (more directly) use
> > Samba's debug support. At the moment we are doing file and syslog
> > logging using CTDB's own backends, which are hooked into debug.[ch]
> > using the DEBUG_CALLBACK support.
> Hey Martin,
> thanks for looking into this mess!
> > We have come across (at least!) a couple of idiosyncrasies in
> > debug.[ch]... :-)
> > * Headers and messages can be interleaved in file logging
> > Header and message are written using 2 separate write() calls (via
> > dbghdrclass(), dbgtext()). So, if 2 processes are writing to the same
> > log file, then you can get <header1>, <header2>, <message1>,
> > <message2>... or other variations.
> > This could be improved if the above 2 functions added to the buffer
> > and a single write() was then used.
> > * When logging to syslog, header information is duplicated
> > That is the date and time (and maybe PID, progname), are present in
> > the output of dbghdrclass() and syslog adds them as well.
> > All the backends other than file (syslog, systemd, lttng,
> > GPFS) probably add their own timestamps.
> > This could be improved by having dbghdrclass() omit these items and
> > have the file backend add those that are configured.
> > For CTDB logging we only really want single-line messages, with an
> > appropriate non-redundant header. For file we want a header
> > (date, time, progname, pid). For syslog we want to send just a bare
> > message and have syslog do the rest.
> > Suggestions? Ideas? :-)
> Please take a look into the options:
> debug prefix timestamp
> timestamp logs
> They are related and are totally broken.
Well, I don't think they're totally broken. If you read the
documentation very carefully then "debug prefix timestamp" does what it
However, there should really be 3 options:
debug location = Add the file location
debug function = Add the function name
debug header prefix = Don't add a newline after header
This is all somewhat broken for non-file output, since the header and
text are logged via separate calls to the backend. I have a branch
that could fix this, since I've pushed logging of the header into the
backend. However, at the moment I still use a separate call for
the header. This essentially makes DEBUG_ADD() useless, since it
prints the last header that was produced - however, at least no time is
taken to generate the extra header right now.
> The suggestion I have is that we need tests for the debug system. We have
> features which do not work and nobody notices.
> Testing debug is possible using the Mock object  support in cmocka .
I agree and will look into it. However, I don't have an endless bucket
of time for this. One problem is that I doubt testing would have
caught either of the issues I listed above! ;-)
peace & happiness,
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