new features in RRDtool: add/delete DSs and RRAs in existing RRD base

[Bigunyak Dmitry]

Hello!

I have tried to find solution how to add/remove data sources or RRA in  
existing RRD base in mailing list archive and saw many questions on this  
theme. With respect to data sources some peoples suggest to use script  
founded in the contrib directory as solution. This script works in next  
sequence: dumps RRD base in XML-file, then edits this file and finely  
restores new RRD base from it. I use this solution too, but I can?t say  
that this is a good approach, first of all because of its low performance.  
In my opinion RRDtool needs to have its internal mechanism to solve this  
issue. But I havn?t found anything similar in plans for RRDtool 1.4. Why?  
Maybe you think that such mechanism in RRDtool this is not a good idea, or  
not useful feature? All the same about working with RRA. I think this  
features will make RRDtool much more flexible. What do say about this?

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[Alex van den Bogaerdt]

On Fri, May 09, 2008 at 03:41:59PM +0400, Bigunyak Dmitry wrote:
> Hello!
>
> I have tried to find solution how to add/remove data sources or RRA in  
> existing RRD base in mailing list archive and saw many questions on this  
> theme. With respect to data sources some peoples suggest to use script  
> founded in the contrib directory as solution. This script works in next  
> sequence: dumps RRD base in XML-file, then edits this file and finely  
> restores new RRD base from it. I use this solution too, but I can?t say  
> that this is a good approach, first of all because of its low performance.  

If you're going to use the script only once, performance is not really
an issue in most cases.

If you need to use such a feature many times, chances are something's
wrong in other places, such as research&development, when designing
the database.

> In my opinion RRDtool needs to have its internal mechanism to solve this  
> issue. But I havn?t found anything similar in plans for RRDtool 1.4. Why?  

I can only guess: because you can create another database with the
same RRAs and such, containing the new DS.


--
Alex van den Bogaerdt
http://www.vandenbogaerdt.nl/rrdtool/

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[Tobias Oetiker-3]

Hi Bigunyak,

the 'problem' is that the on-disk data format of rrdtool does not
lend it sels to adding and removing data sources ... all that can
be done sensibly is to reqrite the file in its new structure ...

if you are planning to work on something like this, you are most
welcome ...

another thing people often ask is to changeing the step size of an
archive ... it would be an interesting task to write a rrdtool
re-sampling mechanism which is able to alter the step size of an
existing archive while keeping the data as intact as possible ...

cheers
tobi



Today Bigunyak Dmitry wrote:

> Hello!
>
> I have tried to find solution how to add/remove data sources or RRA in
> existing RRD base in mailing list archive and saw many questions on this
> theme. With respect to data sources some peoples suggest to use script
> founded in the contrib directory as solution. This script works in next
> sequence: dumps RRD base in XML-file, then edits this file and finely
> restores new RRD base from it. I use this solution too, but I can?t say
> that this is a good approach, first of all because of its low performance.
> In my opinion RRDtool needs to have its internal mechanism to solve this
> issue. But I havn?t found anything similar in plans for RRDtool 1.4. Why?
> Maybe you think that such mechanism in RRDtool this is not a good idea, or
> not useful feature? All the same about working with RRA. I think this
> features will make RRDtool much more flexible. What do say about this?
>
>

--
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten
http://it.oetiker.ch tobi@... ++41 62 213 9902

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[Alex van den Bogaerdt]

On Fri, May 09, 2008 at 07:25:45PM +0200, Tobias Oetiker wrote:
> Hi Bigunyak,
>
> the 'problem' is that the on-disk data format of rrdtool does not
> lend it sels to adding and removing data sources ... all that can
> be done sensibly is to reqrite the file in its new structure ...

Which will be faster than the dump-edit-restore procedure.
But who really needs that?

> another thing people often ask is to changeing the step size of an
> archive ... it would be an interesting task to write a rrdtool
> re-sampling mechanism which is able to alter the step size of an
> existing archive while keeping the data as intact as possible ...

Averages won't be a problem, but how to deal with minimum,maximum and last?
One thing's for sure: without the original input, any change will be
guesswork except for the special case where the new step size is a
whole integer times the old step size.

E.g. LAST:

Consider 300 seconds per interval, being changed into 200 seconds
per interval. Each time the rate was 0 for the larger part of the
interval, except at the end (0,0...0,1,1},{0,0...0,1,1} -> 1,1.
Result: 600 seconds rate 1, in two intervals.  The sensible thing
to do would to change this into 3 intervals of 200 seconds, also
with rate 1: 1,1 -> 1,1,1.

But, with the original input available, the sensible thing to do
would be to change this into two intervals with rate 0 and one
with rate 1: {0,..,0},{0,..,1,1,0,0...,0},{0,..,0,1,1} -> 0,0,1


E.g. MAX:

The same input as above would result in 1,1 being changed into 1,1,1
but with the original input available the result would be 0,1,1.

(0,0...0,1,1},{0,0...0,1,1} -> 1,1 -> 1,1,1.
{0,..,0},{0,..,1,1,0,0...,0},{0,..,0,1,1} -> 0,1,1



I think you would be opening a can of worms.
Alex

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[Bigunyak Dmitry]

On Fri, 09 May 2008 21:25:45 +0400, Tobias Oetiker <tobi@...> wrote:

> Hi Bigunyak,
>
> the 'problem' is that the on-disk data format of rrdtool does not
> lend it sels to adding and removing data sources ... all that can
> be done sensibly is to reqrite the file in its new structure ...
>
> if you are planning to work on something like this, you are most
> welcome ...
>
> another thing people often ask is to changeing the step size of an
> archive ... it would be an interesting task to write a rrdtool
> re-sampling mechanism which is able to alter the step size of an
> existing archive while keeping the data as intact as possible ...
>
> cheers
> tobi
>

Hello, thanks for reply!

Now I understand why it's so hard to make. But it's very useful feature  
not only for me and if someone will make it this will be great! Today  
nothing stay to do except to use procedure dump-edit-restore.

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e-mail: icestar@...

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[Sebastian Harl]

Hi,

On Fri, May 09, 2008 at 03:41:59PM +0400, Bigunyak Dmitry wrote:
> I have tried to find solution how to add/remove data sources or RRA in  
> existing RRD base in mailing list archive and saw many questions on this  
> theme. With respect to data sources some peoples suggest to use script  
> founded in the contrib directory as solution. This script works in next  
> sequence: dumps RRD base in XML-file, then edits this file and finely  
> restores new RRD base from it.

Just a short pointer:

The RRD::Simple perl module ([1]) includes a function to add new DS's.
It uses the dump, modify, restore mechanism as well, so the main benefit
is that you don't have to do that by hand.

Cheers,
Sebastian

[1] http://search.cpan.org/~nicolaw/RRD-Simple-1.44/lib/RRD/Simple.pm

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Those who would give up Essential Liberty to purchase a little Temporary
Safety, deserve neither Liberty nor Safety.         -- Benjamin Franklin



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