: so i edit the solrconfig.xml in tht file to add clustering information (i : did make sure that the lib declaration points to the correct location).
are you sure? ... did you see log messages (prior to the stack trace below) inidcating that the clustering jar was being loaded? SolrResourceLoader logs an info message for every jar it loads, so if you don't see the clustering jar in that list, that's why it can't find it. (and even if you do see it, it might be getting loaded by a differnet core then the one you are trying to use it in, so initializing Solr with a single core first to sanity check may be a good idea) -Hoss
