Thank you for your pointers. sstablemetadata seem's explain that we have
data without ttl (= 0) I don't know how can appears in ours system.
- I replace our ttl by query by the default ttl.
- I reduce the gc grace seconds to one day
- I apply the unchecked_tombstone_compaction (on 31 days of data we have
very few query on data more than 7 days old)
I will manually clean up the old sstable that will never be dropped.
We will seen if it's good for us.
Le 06/10/2021 à 11:58, Paul Chandler a écrit :
Hi Michael,
I have had similar problems in the past, and found this Last Pickle post very
useful: https://thelastpickle.com/blog/2016/12/08/TWCS-part1.html
This should help you pinpoint what is stopping the SSTables being deleted.
Assuming you are never manually deleting records from the table then there is
no need to have a large gc_grace_seconds, as a large one is there to ensure
tombstones are replicated correctly, and you won’t have any tombstones to worry
about.
If you are doing manual deletes, then that could be the cause of the issue, I
wrote a post here about why that would be an issue:
http://www.redshots.com/cassandra-twcs-must-have-ttls/
After reading these if you are still having problems please let us know.
Thanks
Paul
On 6 Oct 2021, at 09:42, Michel Barret <michel.bar...@inovatel.com> wrote:
Hello,
I try to use cassandra (3.11.5) with 8 nodes (in single datacenter). I use one
simple table, all data are inserted with 31 days TTL (the data are never
updated).
I use the TWCS strategy with:
- 'compaction_window_size': '24'
- 'compaction_window_unit': 'HOURS'
- 'max_threshold': '32'
- 'min_threshold': '4'
Each node run one time by week a 'nodetool repair' and our gc_grace_seconds is
set to 10 days.
I track the storage of nodes and the partition used for cassandra data (only
use for this) is consuming to ~40% after one month.
But cassandra consume continuously more space, if I read the sstables with
sstabledump I find very old tombstones like it :
"liveness_info" : { "tstamp" : "2021-07-26T08:15:00.092897Z", "ttl" : 2678400, "expires_at" :
"2021-08-26T08:15:00Z", "expired" : true }
I don't understand why this tombstone isn't erased. I believe that I apply all
I found on internet without improvement.
Anybody had a clue to fix my problem?
Have a nice day
