[rrd-users] Time Shift on Trend Graph

[Ryan Kubica]

Chris,

You're probably talking to yourself; but I'll reply anyway. :-)

In order to get the 'first' you have to read all the data in ... there's no function for it.  Think of it this way, it's a round robin database, so let's pretend you have a 3 month RRA.  What's the first record?  If you've been writing for 4 months; the oldest is 3 months ago, if you've been writing for 1 month it would be 1 month ago.  RRD doesn't keep track of that, it keeps track of offsets into the RRA for efficient updates/reads.  It's not a useful feature for it to keep track of a 'first' since most RRDs will exist longer than a true first.

I've never heard of anyone wanting a view like you describe, most data views are expected to be fixed time-spans so each is visually(or xported) comparable to  


Since it would be inefficient even on your part to scan the set for the 'supposed first' my suggestion is you have a database ( or simple flat file ) keep track of when you created the datafile and always use that.  It'll look weird (blank) on your graphs as the RRA ages past the point of it rolling over ( round robin ) but you would get your feature.

HTH,
-Ryan


________________________________
 From: Chris Mason <chris at netnix.org>
To: "rrd-users at lists.oetiker.ch" <rrd-users at lists.oetiker.ch> 
Sent: Monday, July 1, 2013 3:27 AM
Subject: Re: [rrd-users] Time Shift on Trend Graph
 


Hi,

I am assuming "rrdtool last" returns the actual last time because when you add new data to the RRD, it rotates the RRD and the stuff that was previously at the beginning interval is pushed out - to always maintain the same length and size of an RRD - you are always adding to the end?

I am starting to conclude, after getting the feeling that I am talking to myself, that I can't obtain the point in my RRD when I first entered data? Would it not be the first non-unknown value in the data source and can I obtain this easily to use this to determine the start time of my graph?

Thanks,
Chris






On 28 June 2013 14:45, Chris Mason <chris at netnix.org> wrote:

Hi,
>
>
>I have been through the documentation and I can't seem to find a way for the graph to grow from the left instead of the right.
>So, I thought I might try and do it manually by fetching the "first" entry from the rrd - similar to the "last" function.
>
>
>However, as I should have expected, although last returns the last input into the rrd, first is returning the first entry for the RRA, not the first time that I inserted data.
>
>
>Is there any way to determine the first time I inserted data into the RRA as opposed to the start of the RRA period?
>
>
>Thanks,
>Chris
>
>
>
>On 25 June 2013 16:05, Chris Mason <chris at netnix.org> wrote:
>
>Hi,
>>
>>
>>I suppose the other option, if I am unable to achieve what I wanted, is to only draw the trend line from the start of the actual data.
>>I use the following logic to draw a trend line for data source "DS1":
>>
>>
>>VDEF:DS1Slope=DS1,LSLSLOPE
>>VDEF:DS1Int=DS1,LSLINT
>>CDEF:DS1Trend=DS1,POP,COUNT,DS1Slope,*,DS1Int,+,0,INF,LIMIT
>>
>>LINE1:DS1Trend#808080::dashes';
>>
>>
>>
>>Is it possible to restrict the trend line to start when my data started instead of at the beginning of the graph?
>>I would assume that any value within DS1 that was before my data would be classified as unknown - is my DS1Trend CDEF removing the unknowns?
>>
>>
>>Thanks,
>>Chris
>>
>>
>>
>>On 23 June 2013 13:17, Chris Mason <chris at netnix.org> wrote:
>>
>>Hi,
>>>
>>>
>>>I have the following graph which displays daily maximums over a period of a year:
>>>
>>>
>>>http://netnix.org/graph.png
>>>
>>>
>>>
>>>I have added a trend line to the graph using the Least Square Lines method. I am currently shifting the graph by 3 months using the following method:
>>>
>>>
>>>-s -1y+3months -e now+3months
>>>
>>>
>>>This works fine, but I wanted to try and shift the graph so the start of the graph is at the left most point and the graph is only ever displayed in the first 9 month period. It is easy if I only ever had more than 9 months worth of data, but if I only had 3 months worth of data, then I am looking for the graph to still start from the left with only the left 3 months being used?
>>>
>>>
>>>I am looking to try and do something similar to the "Filesystem Utilization and Predicted Trends" graph in the RRDTOOL gallery where in the picture, the graph is using the left hand side and the trends go into the right hand side.
>>>
>>>
>>>Any pointers?
>>>
>>>
>>>Thanks,
>>>Chris
>>
>

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