I documented this on JIRA. Please see CASSANDRA-11025 <https://issues.apache.org/jira/browse/CASSANDRA-11025>
On Sun, Jan 17, 2016 at 11:48 PM, Sebastian Estevez < sebastian.este...@datastax.com> wrote: > 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 >>> >> >> -- *陈硕* *Shuo Chen* chenatu2...@gmail.com chens...@whaty.com
