On Wed, Jul 11, 2012 at 7:13 AM, Rob Marianski <[email protected]> wrote: > A user running geoserver on windows noticed that when using a > cascading wms layer, temporary files were being written out to disk > for each request. We investigated, and stumbled across this > explanation: > > http://frequal.com/java/PreventUnexpectedImageIODiskWrites.html > > It turns out that it actually resolved the issue. To verify, we > created a GeoServerInitializer in a separate module, and the jar was > added to geoserver. There were no more writes on the requests. > > Are there any possible consequences here? If not, can this be set on > geoserver startup in general? And if this isn't something that should > be set globally for everybody, is it reasonable to create a > GeoServerInitializer and put the call in there?
The are consequences, such move can undermine the server stability in a severe way and make it go OOM very often under the right kind of load. When reading and writing images to or from generic I/O streams ImageIO has to wrap the stream into a memory buffer or file buffer image stream, which is not really a stream anymore, but a full random access structure. This is required because both when reading and writing images it happens that one has to jump back and forth. If one forces the usage of memory buffers (disabling the cache usage fully) the consequences is that the png you are trying to read from the remote WMS is fully read in memory, and that 200GB geotiff that someone might be trying to get out of WCS is also fully written in memory before being streamed out: you basically give up control on the amount of heap memory each request is using, leaving GeoServer at the mercy of the users and the events. If you look into the settings you'll find a threshold at which the current system decides whether to use a memory or a file based imageinputstream (and the same goes for the output). The above system requires image reading/writing code to use the GeoTools ImageIOExt class to get the image input streams, something that the WMSCoverageReader is indeed not doing. That indeed needs fixing, jira + patch welcomed Cheers Andrea -- Ing. Andrea Aime GeoSolutions S.A.S. Tech lead Via Poggio alle Viti 1187 55054 Massarosa (LU) Italy phone: +39 0584 962313 fax: +39 0584 962313 mob: +39 339 8844549 http://www.geo-solutions.it http://geo-solutions.blogspot.com/ http://www.youtube.com/user/GeoSolutionsIT http://www.linkedin.com/in/andreaaime http://twitter.com/geowolf ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Geoserver-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geoserver-users
