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List:       collectd
Subject:    Re: [collectd] Version 5.0.0.beta0 available
From:       Florian Forster <octo () collectd ! org>
Date:       2010-12-08 17:17:02
Message-ID: 20101208171702.GE2398 () verplant ! org
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Hi Thorsten,

On Wed, Dec 08, 2010 at 09:04:55AM -0800, Thorsten von Eicken wrote:
> Has the network protocol changed?

a little. v5 uses a much higher accuracy to specify time. This is
represented in an addition to the protocol, which v4 servers don't
understand.

> Can a v5 client send to a v4 server?

No, because without a timestamp the data is invalid. Or maybe just
erroneous and you'll receive tons of error. I didn't try.

> Any issues when a v4 client sends to v5?

In theory, this should work. Finding out if this works as expected is
what I hope to achieve with the beta version.

> You don't state these things explicitly anywhere.

I'll try to improve the wiki page and possibly other accompanying
documentation.

> The situation we're gonna be in is that we'll have a mix of v4 and v5
> clients sending data to the same servers. I'm wondering whether there's
> any easy way to flag the resulting rrds.

The RRD layout, for example whether the "cpu" type uses COUNTER or
DERIVE, depends on the version of the server -- the client version has
no influence on that. Again, for front-ends this is negligible.

> I know I can open the rrd and list the ds names, but right now I have
> a config table that maps rrd > filename to ds names (and associated
> config).

Same for the DS names. So you could use the CTIME to determine whether a
file was created before or after the server was updated to 5.0. But I'd
strongly recommend to convert the RRD files with the migration script.
Both, v4 and v5 servers could update those RRD files. If a v4 server
creates a new file it will have a "wrong" DS name, though, and you may
need to re-run the migration script.

> Another thought: would it be possible to insert a "shim" into the v5
> server's stack (perhaps close to the network input) that converts v4
> data to v5 data? It would have to use some heuristics, but it might
> not be that bad.

This is *exactly* what the "v5upgrade" target does. It'd be great if you
could share any experience you may have with this tool. Its wiki page is
at <http://collectd.org/wiki/index.php/Target:v5_upgrade>

Thanks for your questions, it really does help to pinpoint where more
documentation is necessary!

Regards,
--octo
--=20
Florian octo Forster
Hacker in training
GnuPG: 0x0C705A15
http://octo.it/

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