resolution doesn't work with Rrd4j

[Maxim Kopeyka]

I'm working with migration from JRobin to Rrd4j and I'm stack with wrong data export from Rrd4j;

JRobin example

RrdExportDef expDef = new RrdExportDef(1420502400, 1422883200);

expDef.datasource(dsName, rrdFile.getAbsolutePath(), dsName, "AVERAGE");

RrdExport exp = new RrdExport(expDef);

ExportData data = exp.fetch(resolution);

data.exportXml(String.format("%s.old.xml", rrdName)); 

Values depend on resolution, I have different values with different resolution

Rrd4j example

 

FetchRequest request = rrddb.createFetchRequest(ARC_TYPE, 1420502400, 1422883200, resolution);

FetchData fetchData = request.fetchData();

fetchData.exportXml(format("d:/temp/%s.xml", path));

Values not depend on resolution, I see the same values with different resolution

Import JRobin to Rrd4j

File rrdXmlFile = File.createTempFile(fileDetails.getFile().getName(), ".xml");

RrdDb rrddb = new RrdDb(fileDetails.getFile().getAbsolutePath());

rrddb.dumpXml(rrdXmlFile.getAbsolutePath());

rrddb.close();

 

org.rrd4j.core.RrdDb mongoRrdDb = new org.rrd4j.core.RrdDb(fileDetails.getRelativePath(), rrdXmlFile.getCanonicalPath(), factory);

mongoRrdDb.close();

[Fabrice Bacchella]

You don't compare the same code. Why do you expect the same results ?

RrdExportDef is not any more in jrobin code :

https://github.com/OpenNMS/jrobin/tree/master/src/main/java/org/jrobin/graph

So what do you expect exactly ?

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[Maxim Kopeyka]

I expected parameter resolution works somehow, i.e. I should see different values in case I use different resolutions.

[Maxim Kopeyka]

I've tested the latest JRobin lib, it doesn't work properly with resolution too.

[Maxim Kopeyka]

So, I've tested 3 libraries

1. JRobin 1.4.0
2. JRobin 1.5.14
3. rrd4j

The method createFetchRequest ignores resolution in all these libraries, i.e. I have the same output from all of them.

But JRobin 1.4.0 has RrdExportDef and RrdExport classes and RrdExport doesn't ignore resolution and provides different values for different resolutions

The RrdExport provides correct values even I do this import/export of rrd file:

JRobin 1.4.0 --> rrd4j --> JRobin 1.5.14 --> JRobin 1.4.0

[Fabrice Bacchella]

It's explained in the javadoc :

     * Prepares fetch request to be executed on this RRD. Use returned

     * <code>FetchRequest</code> object and its {@link org.rrd4j.core.FetchRequest#fetchData() fetchData()}

     * method to actually fetch data from the RRD file.

     *

     * @param consolFun  Consolidation function to be used in fetch request.

     * @param fetchStart Starting timestamp for fetch request.

     * @param fetchEnd   Ending timestamp for fetch request.

     * @param resolution Fetch resolution (see RRDTool's

     *                   <a href="http://oss.oetiker.ch/rrdtool/doc/rrdfetch.en.html" target="man">rrdfetch man page</a> for an

     *                   explanation of this parameter.

     * @return Request object that should be used to actually fetch data from RRD

So please read http://oss.oetiker.ch/rrdtool/doc/rrdfetch.en.html.

[Maxim Kopeyka]

I've already checked it and create a for loop to see what steps will be returned

for (long resolution = 1; resolution < 1000000; resolution++){

    long endTime = new Long(1422883200/resolution)*resolution;

    long startTime = new Long(1420502400/resolution)*resolution;

    FetchRequest request = rrddb.createFetchRequest(ARC_TYPE, startTime, endTime, resolution);

}

So, I have got these unique steps

• 300
  
• 1800

What should be done on my side to have step=2400 for example?

[Fabrice Bacchella]

I'm not sure there is a way to do that.