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Re: [pcp] qa/986 and the dmcache pmda

To: Ken McDonell <kenj@xxxxxxxxxxxxxxxx>
Subject: Re: [pcp] qa/986 and the dmcache pmda
From: Nathan Scott <nathans@xxxxxxxxxx>
Date: Sun, 10 Aug 2014 20:24:42 -0400 (EDT)
Cc: pcp@xxxxxxxxxxx
Delivered-to: pcp@xxxxxxxxxxx
In-reply-to: <094701cfb4e4$d4ca61d0$7e5f2570$@internode.on.net>
References: <094701cfb4e4$d4ca61d0$7e5f2570$@internode.on.net>
Reply-to: Nathan Scott <nathans@xxxxxxxxxx>
Thread-index: Ac+04sjZna9RuA/WRmupvwbH0NniFxYNwMr7
Thread-topic: qa/986 and the dmcache pmda
Hi Ken,

----- Original Message -----
> All metrics from the dmcache pmda are returning Resource temporarily
> unavailable.
> 
> And the pmda's log file contains ...
> 
> Traceback (most recent call last):
>   File "/var/lib/pcp/pmdas/dmcache/pmdadmcache.python", line 208, in
> dmcache_refresh
>     self.caches[name] = DmCacheStats(line)  # extract stats values
>   File "/var/lib/pcp/pmdas/dmcache/pmdadmcache.python", line 48, in __init__
>     self.parse(text)
>   File "/var/lib/pcp/pmdas/dmcache/pmdadmcache.python", line 61, in parse
>     mbsize = long(data[4]) * 512      # metadata block size (from sectors)
> IndexError: list index out of range

This looks like it may be a genuine bug...

> This is on a Debian 3.2.0 kernel, where dm-cache does not appear to be an
> available kernel module
> 
> $ sudo modprobe dm-cache
> FATAL: Module dm-cache not found.
> 
> and there is no "notrun" guard in this QA test and the test does not set
> $DM_STATUS.

That's all OK, and as expected.  (qa/985 is the test that sets DM_STATUS)

This test (986) is just prodding the running kernel, whether it supports
dm-cache or not, and seeing that we get sensible behaviour when asking
for values.  The actual verification of values is left to qa/985 - so
no values is an expected & valid scenario here.

What is on stdout from "dmsetup status --target=cache" (as root) on the
test machine?  I think we're getting something back, when we expect not
to get anything, and the parser doesn't handle whatever it gets...

thanks!

--
Nathan

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