Threshold with CDEF'd graphs, i.e. Disk space by percentage

benhanson · Post by **benhanson** » Tue Mar 22, 2005 2:47 pm

Would there be any way to have the threshold module alert on a CDEF value? I've just figured out how to graph my drive space based on percentage rather than bytes free, only to realize that now I can't alert on the percent value since it is not an actual data source in the RRD. If you could do this, you would gain all of the flexibility of CDEF's in alerting as well.

Example:

Disk bytes free has 2 Data Sources: hdd_total and hdd_used
I can set a threshold on these. I've changed my graphs by adding a new graph item with no source, but a CDEF - a,b,/,100,*

ABX · Post by **ABX** » Mon Nov 12, 2007 8:38 am

I'd like to see this too.

Cacti 0.8.7

ejensen · Post by **ejensen** » Mon Nov 12, 2007 9:15 am

can you share with us how to setup a CDEF to calculate the percentage?

an idea i have (forgive me if its stupid, i am kinda new to cacti)... could you just setup a new datasource that stores the percentage from the disk?

benhanson · Post by **benhanson** » Tue Nov 13, 2007 12:48 pm

The CDEF formula is there in my first message, a,b,/,100,*

I was never able to set a threshold on this, but I haven't tried in quite a few versions.

looc · Post by **looc** » Fri Nov 16, 2007 4:53 am

benhanson wrote:The CDEF formula is there in my first message, a,b,/,100,*

I was never able to set a threshold on this, but I haven't tried in quite a few versions.

how defined a&b?
and how calculate this formula?
a/b*100?!

looc · Post by **looc** » Fri Nov 16, 2007 5:09 am

you want to used these?
DEF:a="E\:/www/rra/localhost_hdd_used_9.rrd":hdd_total:AVERAGE \
DEF:b="E\:/www/rra/localhost_hdd_used_9.rrd":hdd_used:AVERAGE \
DEF:a&DEF:b?
custom string can define These two variables?

llow · Post by **llow** » Tue Dec 04, 2007 4:59 pm

Here is a patch that will allow you to use the ALL_DATA_SOURCES_DUPS and ALL_DATA_SOURCES_NODUPS (they will perform the same since this is based on the data soruce and not the graph.

Example use:

Data source with mem_used and mem_free.
Create threshold on mem_used and use a CDEF of CURRENT_DATA_SOURCE,100,*,ALL_DATA_SOURCES_NODUPS,/ and you will get a percentage of mem_used.

There should only be a performance impact if this DS is used and it only pertains to an extra sql query.

llow · Post by **llow** » Wed Dec 05, 2007 12:59 pm

Here is a better patch, will only perform one lookup of the data source. There is some problem I am having an odd problem with no data being returned from rrdtool_function_fetch on the hdd rrds.

Howie · Post by **Howie** » Tue Jan 29, 2008 1:58 pm

llow wrote:Here is a better patch, will only perform one lookup of the data source. There is some problem I am having an odd problem with no data being returned from rrdtool_function_fetch on the hdd rrds.

llow, did you solve your hdd problem? I have just tried your patch, and I'm seeing an issue too. Unfortunately, hdd's are all I care about at the moment

llow · Post by **llow** » Tue Jan 29, 2008 3:30 pm

It will only work "properly" if the rras used are updated at the same time. I have about 600 routers where I pull % of memory and have no issue. I use the UCD-SNMP mib for all my Linux servers and have no issue.

The only problem is when I use the HOST-MIB with a script server that returns hdd_free and hdd_used and since the script server is called multiple times there is a problem with having the hdd_free and hdd_used updated by the time the thold poll is taken. This is especially more difficult in my setup where my HDD data is polled at 5 minutes but my poller runs every minute. The two data sources may not even be polled in the same poller interval.

I haven't come up with a good idea to solve this yet as I would like to have the script server be able to handle data like data input methods can.

I think this is more of something that needs to be solved in the base code instead of directly within Threshold.

Howie · Post by **Howie** » Sun Feb 03, 2008 12:05 pm

OK. I think I have this working now.

First of all, I'm using a different query than llow for the CDEF part - I don't really understand the one they used - $ds is a field name - when would it ever be in the id field? I skipped the changes to get_current_value(), but I would say that I was getting type-related errors from your patch, one of which I fixed with:

Code: Select all

// NOT THIS ->   if (!is_array($ds)) $ds[0] = $ds;
       if (!is_array($ds)) { 
         $ds_tmp = $ds;
         $ds = array();
         $ds[0] = $ds_tmp;
      }

I then ended up rewriting the RPN code in thold to actually do RPN properly with a stack, since my valid CDEF had two operators in a row, which threw off thold.

So here's a different patch against the original thold_functions.php, with improved RPN handling and ALL_DATA_SOURCES implemented.

I don't use 1 minute polling on this particular install, so I doubt anything has changed there.

llow · Post by **llow** » Tue Feb 05, 2008 2:48 pm

I'll have to check out your ideas. Any chance you could post a patch in unified format as it is much easier to read changes

Howie · Post by **Howie** » Tue Feb 05, 2008 5:40 pm

llow wrote:I'll have to check out your ideas. Any chance you could post a patch in unified format as it is much easier to read changes

Sure here you go. It has a little more than it needs to have, because I cleaned up the indenting inside the case statement

mcutting · Post by **mcutting** » Wed Feb 06, 2008 1:39 am

Howie - do you have a patched php file for us windows uers ?

Thanks

cyrill · Post by **cyrill** » Wed Feb 06, 2008 11:39 am

Hello !

I'm a newbie with cacti and my english is bad. Can you help me ? A new CDEF should be created ???

Can you explain me how can I created it and how it work ?

thanks for your help

Cacti

Threshold with CDEF'd graphs, i.e. Disk space by percentage

Threshold with CDEF'd graphs, i.e. Disk space by percentage

CDEF

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