Hi
> Long GC Pauses take about one minute. But why it takes so much time and > how that can be fixed? This is very long. Looks like you are having a major issue, and it is not just about dropping tables... Or is it on happening during drop table actions? Knowing the complete set of GC options in use could help here, could you paste it here (or link to it)? Also, GC is often high as a consequence of other issues and not only when 'badly‘ tuned - Have you had a look at logs, mainly errors and warnings? $ grep -e "ERROR" -e "WARN" /var/log/cassandra/system.log - Are they some pending, blocked or dropped tasks in thread pool stats? $ watch -d nodetool tpstats - Are some resources constraint (CPU / disk IO,...)? We have about 60 keyspaces with about 80 tables in each keyspace In each keyspace we also have 11 MVs Even if I believe we can dig it and maybe improve things, I agree with Carlos, this is a lot of Tables (4880) and even more a high number of MV (660). It might be interesting splitting it somehow if possible. Cannot achieve consistency level ALL Finally you could try to adjust the corresponding request timeout (not sure if it is the global one or the truncate timeout), so it may succeed even when nodes are having minutes GC, but it is a workaround as this minute GC will most definitely be an issue for the client queries running (default is 10 sec timeout, so many query are probably failing). C*heers, ----------------------- Alain Rodriguez - @arodream - al...@thelastpickle.com France The Last Pickle - Apache Cassandra Consulting http://www.thelastpickle.com 2017-04-25 13:58 GMT+02:00 Bohdan Tantsiura <bohdan...@gmail.com>: > Thanks Zhao Yang, > > > Could you try some jvm tool to find out which thread are allocating > memory or gc? maybe the migration stage thread.. > > I use Cassandra Cluster Manager to locally reproduce the issue. I tried to > use VisualVM to find out which threads are allocating memory, but VisualVM > does not see cassandra processes and says "Cannot open application with > pid". Then I tried to use YourKit Java Profiler. It created snapshot when > process of one cassandra node failed. http://i.imgur.com/9jBcjcl.png - > how CPU is used by threads. http://i.imgur.com/ox5Sozy.png - how memory > is used by threads, but biggest part of memory is used by objects without > allocation information. http://i.imgur.com/oqx9crX.png - which objects > use biggest part of memory. Maybe you know some other good jvm tool that > can show by which threads biggest part of memory is used? > > > BTW, is your cluster under high load while dropping table? > > LA5 was <= 5 on all nodes almost all time while dropping tables > > Thanks > > 2017-04-21 19:49 GMT+03:00 Jasonstack Zhao Yang < > zhaoyangsingap...@gmail.com>: > >> Hi Bohdan, Carlos, >> >> Could you try some jvm tool to find out which thread are allocating >> memory or gc? maybe the migration stage thread.. >> >> BTW, is your cluster under high load while dropping table? >> >> As far as I remember, in older c* version, it applies the schema mutation >> in memory, ie. DROP, then flush all schema info into sstable, then reads >> all on disk schema into memory (5k tables info + related column info).. >> >> > You also might need to increase the node count if you're resource >> constrained. >> >> More nodes won't help and most probably make it worse due to coordination. >> >> >> Zhao Yang >> >> >> >> On Fri, 21 Apr 2017 at 21:10 Bohdan Tantsiura <bohdan...@gmail.com> >> wrote: >> >>> Hi, >>> >>> Problem is still not solved. Does anybody have any idea what to do with >>> it? >>> >>> Thanks >>> >>> 2017-04-20 15:05 GMT+03:00 Bohdan Tantsiura <bohdan...@gmail.com>: >>> >>>> Thanks Carlos, >>>> >>>> In each keyspace we also have 11 MVs. >>>> >>>> It is impossible to reduce number of tables now. Long GC Pauses take >>>> about one minute. But why it takes so much time and how that can be fixed? >>>> >>>> Each node in cluster has 128GB RAM, so resources are not constrained >>>> now >>>> >>>> Thanks >>>> >>>> 2017-04-20 13:18 GMT+03:00 Carlos Rolo <r...@pythian.com>: >>>> >>>>> You have 4800 Tables in total? That is a lot of tables, plus MVs? or >>>>> MVs are already considered in the 60*80 account? >>>>> >>>>> I would recommend to reduce the table number. Other thing is that you >>>>> need to check your log file for GC Pauses, and how long those pauses take. >>>>> >>>>> You also might need to increase the node count if you're resource >>>>> constrained. >>>>> >>>>> Regards, >>>>> >>>>> Carlos Juzarte Rolo >>>>> Cassandra Consultant / Datastax Certified Architect / Cassandra MVP >>>>> >>>>> Pythian - Love your data >>>>> >>>>> rolo@pythian | Twitter: @cjrolo | Skype: cjr2k3 | Linkedin: >>>>> *linkedin.com/in/carlosjuzarterolo >>>>> <http://linkedin.com/in/carlosjuzarterolo>* >>>>> Mobile: +351 918 918 100 <+351%20918%20918%20100> >>>>> www.pythian.com >>>>> >>>>> On Thu, Apr 20, 2017 at 11:10 AM, Bohdan Tantsiura < >>>>> bohdan...@gmail.com> wrote: >>>>> >>>>>> Hi, >>>>>> >>>>>> We are using cassandra 3.10 in a 10 nodes cluster with replication = >>>>>> 3. MAX_HEAP_SIZE=64GB on all nodes, G1 GC is used. We have about 60 >>>>>> keyspaces with about 80 tables in each keyspace. We had to delete three >>>>>> tables and two materialized views from each keyspace. It began to take >>>>>> more >>>>>> and more time for each next keyspace (for some keyspaces it took about 30 >>>>>> minutes) and then failed with "Cannot achieve consistency level ALL". >>>>>> After >>>>>> restarting the same repeated. It seems that cassandra hangs on GC. How >>>>>> that >>>>>> can be solved? >>>>>> >>>>>> Thanks >>>>>> >>>>> >>>>> >>>>> -- >>>>> >>>>> >>>>> >>>>> >>>> >>> >
