Invalidate block cache for a reader on close and

Test case for reader cache
Guava has stats API. You can get hits/miss stats from that.  http://docs.guava-libraries.googlecode.com/git-history/release12/javadoc/com/google/common/cache/CacheStats.html.  You can add the boolean parameter recordStat to createCache method and call http://docs.guava-libraries.googlecode.com/git-history/release12/javadoc/com/google/common/cache/CacheBuilder.html#recordStats() method to create cache and then you can call cache.stats() to get all stats of the cache