I agree that this may be worth a jira. Can you clarify this statement?
>>5 keyspaces and about 100 cfs months How many total empty tables did you create? Creating hundreds of tables is a bad practice in Cassandra but I was not aware of a compaction impact like what you're describing. all the best, Sebastián On Jan 16, 2016 4:43 AM, "DuyHai Doan" <doanduy...@gmail.com> wrote: > Interesting, maybe it worths filing a JIRA. Empty tables should not slow > down compaction of other tables > > On Sat, Jan 16, 2016 at 10:33 AM, Shuo Chen <chenatu2...@gmail.com> wrote: > >> Hi, Robert, >> >> I think I found the cause of the too many compactions. I used jmap to >> dump the heap and used Eclipse memory analyzer plugin to extract the heap. >> >> In previous reply, It shows the there are too many pending jobs in the >> Blocking queue. I checked the cf of the compaction task object. There are >> many cfs concerning some empty cfs I created before. >> >> I created 5 keyspaces and about 100 cfs months by cassandra-cli ago and >> didnot put any data yet. In fact, there is only 1 keypaces I created >> containing data and the other 5 keyspaces are empty. >> >> When I droped these 5 keyspaces and restarted the high compaction node, >> It runs normally with normal mount of compactions. >> >> So maybe there are some bugs of compaction for empty columnfamily? >> >> On Wed, Jan 13, 2016 at 2:39 AM, Robert Coli <rc...@eventbrite.com> >> wrote: >> >>> On Mon, Jan 11, 2016 at 9:12 PM, Shuo Chen <chenatu2...@gmail.com> >>> wrote: >>> >>>> I have a assumption that, lots of pending compaction tasks jam the >>>> memory and raise full gc. The full chokes the process and slows down >>>> compaction. And this causes more pending compaction tasks and more pressure >>>> on memory. >>>> >>> >>> The question is why there are so many pending compactions, because your >>> log doesn't show that much compaction is happening. What keyspaces / >>> columnfamilies do you expect to be compacting, and how many SSTables do >>> they contain? >>> >>> >>>> Is there a method to list the concrete details of pending compaction >>>> tasks? >>>> >>> >>> Nope. >>> >>> For the record, this type of extended operational debugging is often >>> best carried out interactively on #cassandra on freenode IRC.. :) >>> >>> =Rob >>> >> >> >> >> -- >> *陈硕* *Shuo Chen* >> chenatu2...@gmail.com >> chens...@whaty.com >> > >
