"Pending compactions" is just an estimate of "how many compactions does Cassandra think it will take to get to fully-compacted state;" there are no actual tasks enqueued anywhere.
You could enable debug logging on org.apache.cassandra.db.compaction, and force a compaction with nodetool to see why no compactions happen when the estimate says there is still work to do. On Fri, Jun 29, 2012 at 4:27 AM, Martin McGovern <martin.mcgov...@gmail.com> wrote: > Hi All, > > Could someone explain why the compaction manager stops compacting when it > has a number of pending tasks? > > I have a test cluster that I am using to stress test IO throughput, i.e. > find out what a safe load for our hardware is. Over a 16 hour period my node > cluster completes approximately 49,000 tasks per node. After stopping my > test compaction continues for a few minutes then stops. There are ~7,000 > tasks still pending. No more tasks will be executed until I start another > test and the 7000 pending will never be executed. > > I'm using leveled compaction with 5MB SS tables and my tests have a 50:50 > read:write ratio. Each value is a 10K byte array with random content. > > Thanks, > Martin -- Jonathan Ellis Project Chair, Apache Cassandra co-founder of DataStax, the source for professional Cassandra support http://www.datastax.com