I think this is a bit extreme. If you know that 100% of all queries that
write to the table include a TTL, not having a TTL on the table is just
fine. You just need to ensure that you always write correctly.
On Wed, Oct 6, 2021 at 8:57 AM Bowen Song <bo...@bso.ng> wrote:
> TWCS without a table TTL is unlikely to work correctly, and adding the
> table TTL retrospectively alone is also unlikely to fix the existing
> issue. You may need to add the table default TTL and update all existing
> data to reflect the TTL change, and then trigger a major compaction to
> update the SSTable files' metadata (specifically, maximum timestamp in
> the SSTable and TTL max, which can be used to calculate the safe time
> for deleting the entire SSTable file). After all the above is done, you
> will need to wait for the table default TTL amount of time before
> everything is back to normal. The reason for the waiting time is because
> the major compaction will result in a single SSTable file expiring in
> the TTL time, and the SSTable will remain on disk until that amount of
> time has passed. So you will need enough disk space for about twice the
> amount of data you are expecting to have in that table.
>
> On 06/10/2021 16:34, Michel Barret wrote:
> > Hi, it's not set before. I set it to ensure all data have a ttl.
> >
> > Thanks for your help.
> >
> > Le 06/10/2021 à 13:47, Bowen Song a écrit :
> >> What is the the table's default TTL? (Note: it may be different than
> >> the TTL of the data in the table)
> >>
> >> On 06/10/2021 09:42, Michel Barret 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
>
