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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



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