[rrd-developers] Update ex post?

[Till Dörges]

Hi,

On 24.08.2010 12:44, Sebastian Harl wrote:

> What other real-world use-cases, other than removing spikes or undefined
> values, are out there? Those are the only ones I've encountered so far.

That's pretty much what we'd be after.

For our particular scenario we can even limit the time window for which we'll accept
an update ex post.

With that particular constraint the most favorite solution right now looks like a
combination of a normal RRDtool db and a MySQL db. The former works as always, except
that it doesn't store updates until t_now but until t_now - t_window. t_window is the
time window for which we'll accept updates ex post. All the data between t_now -
t_window and t_now ends up in MySQL. If any late updates arrive putting them in MySQL
shouldn't be a problem. Graphing the data requires two data sources rather than one
(normal rrdgraph + rrdgraph_libdbi), but that's not too difficult, either.
Periodically data has to be transferred from MySQL to the RRDtool db.

The downsides I can see is that an additional db adds extra complexity. And you have
a bit of effort to put into transferring the data. But you don't loose any of the
nice features of RRDtool and you have the ability to perform late updates (within a
reasonable time window).

Regards -- Till
-- 
Dipl.-Inform. Till Dörges                  doerges at pre-sense.de

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