Re: RDAC path checker status change messages

[Benjamin Marzinski <bmarzins@redhat.com>]

On Thu, Jun 25, 2009 at 01:28:40PM -0400, Charlie Brady wrote:
>
> On Thu, 25 Jun 2009, Charlie Brady wrote:
>
>> On Thu, 25 Jun 2009, Charlie Brady wrote:
>>
>>>  I think I need to retract that. The messages appear to be printed when the
>>>  status is not changing, at least for the "path down" messages.
>>>
>>>  I've patched scsi_dh_rdac.c so that SUN/LCSM100_I is included in
>>>  rdac_dev_list[], and restarted iscsi and multipathd. I've now provoked a
>>>  path failure via iptables. Here are the logs I see (with unpatched
>>>  multipathd) - the duplicate message suppression from the rdac path checker
>>>  is not working:
>>
>> OTOH, on path recovery, the wrong message is displayed ("path down" 
>> instead of "path up") but the message is not repeated:
>
>> From multipathd/main.c, there are three conditions where the messages are 
> printed:
>
> ...
>                         if (newstate != pp->state) {
>                                 int oldstate = pp->state;
>                                 pp->state = newstate;
>                                 LOG_MSG(1, checker_message(&pp->checker));
> ...
>                         }
>                         else if (newstate == PATH_UP || newstate == PATH_GHOST) {
>                                 LOG_MSG(4, checker_message(&pp->checker));
> ...
>                         else if (newstate == PATH_DOWN)
>                                 LOG_MSG(2, checker_message(&pp->checker));
> ...
>
> I think only the first might be required, and only the first will be seen 
> if logging verbosity < 2 (default is 2).
>
> So there are two path checker problems I can see (in 
> multipath-tools-0.4.7.rhel5.13):
>
> - the rdac checker leaves the message set to "path down" when path
>   transitions back to up or ghost.

Any your patch fixes that.

> - multipathd prints the message on every PATH_DOWN except the first when
>   verbosity is >= 2, and on every PATH_UP or PATH_GHOST except the first
>   when verbosity is >= 4.

Why is this a problem? 

On verbosity = 1, you only get messages when you change states.
On verbosity = 2, you additionally get repeated messages for failed
paths, which are often something that the sysadmin should be doing
something about.
On verbosity = 4, you get a message whenever the path checker runs,
which is helpful for debugging, which is the only time you would ever
want verbosity = 4.

This seems sensible to me.  If you don't like the repeated path down
messages, you can change your verbosity level to 1.  Right now that
involves editting the init script, but in future releases, you can
change it in /etc/multipath.conf.

-Ben

>
> ---
> Charlie
>
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