git.net

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: TWCS Compaction backed up


What's your window size?

When you say backed up, how are you measuring that?  Are there pending tasks or do you just see more files than you expect?

On Tue, Aug 7, 2018 at 4:38 PM Brian Spindler <brian.spindler@xxxxxxxxx> wrote:
Hey guys, quick question: 
 
I've got a v2.1 cassandra cluster, 12 nodes on aws i3.2xl, commit log on one drive, data on nvme.  That was working very well, it's a ts db and has been accumulating data for about 4weeks.  

The nodes have increased in load and compaction seems to be falling behind.  I used to get about 1 file per day for this column family, about ~30GB Data.db file per day.  I am now getting hundreds per day at  1mb - 50mb.

How to recover from this? 

I can scale out to give some breathing room but will it go back and compact the old days into nicely packed files for the day?    

I tried setting compaction throughput to 1000 from 256 and it seemed to make things worse for the CPU, it's configured on i3.2xl with 8 compaction threads. 

-B

Lastly, I have mixed TTLs in this CF and need to run a repair (I think) to get rid of old tombstones, however running repairs in 2.1 on TWCS column families causes a very large spike in sstable counts due to anti-compaction which causes a lot of disruption, is there any other way?  




--
Jon Haddad
http://www.rustyrazorblade.com
twitter: rustyrazorblade