Re: Cache

Hi Estani:

yes we are caching catalogs, and we know its inefficient. we have been 
trying to refactor this for a while.

meanwhile, for servers with many static catalogs, you should turn off 
caching:

http://www.unidata.ucar.edu/projects/THREDDS/tech/tds4.2/reference/ThreddsConfigXMLFile.html#CatalogCaching

good to see you in livermore, hope to run into you soon!

john

On 12/8/2011 6:56 AM, Estanislao Gonzalez wrote:
> Hi John,
>
> I haven't got the time to test the new TDS, although I'm eager to :-)
>
> But debugging some other problems (and playing around with new tools 
> from the JDK 1.6) I got this dump of a working TDS:
> Object Histogram:
>
> num       #instances    #bytes  Class description
> -------------------------------------------------------------------------- 
>
> 1:              16076618    1062825760      char[]
> 2:              9141380     524291112       java.lang.Object[]
> 3:              13688352    438027264       java.lang.String
> 4:              8749808 209995392       java.util.ArrayList
> 5:              5077955 162494560       org.jdom.Attribute
> 6:              2093916 150761952       
> org.apache.xerces.impl.xs.opti.ElementImpl
> 7:              3009594 120383760       
> org.apache.xerces.impl.xs.opti.AttrImpl
> 8:              2917424 116696960       org.jdom.Element
> 9:              4277339 102656136       org.jdom.Text
> 10:             2430493 97219720        org.jdom.Attribute[]
> 11:             2920707 93462624        org.jdom.ContentList
> 12:             2917424 93357568        org.jdom.AttributeList
> 13:             69695   93236992        byte[]
> 14:             1390423 85737680        int[]
> 15:             1366453 74250648        org.jdom.Content[]
> 16:             560070  53766720        thredds.catalog.ThreddsMetadata
> 17:             2084070 50306496        org.w3c.dom.Attr[]
> ...
>
> What is being cached exactly? It looks a lot...
> Why are the DOM there?
>
> I think that you might be holding the DOM elements in a strong 
> reference, and those, again, are the one holding the String and, 
> again, the char[].
> Do you need to store the DOM? Is this changing dynamically so often 
> for your other use-cases?
> I would have thought you would want to create the DOM, dump it to a 
> string and hold that string within a SoftReference object to allow GC 
> in case it's needed. The DOM could then GC and would be eligible over 
> the SoftReference (supposedly)
>
> How are you caching the catalogs exactly?
>
> Thanks,
> Estani