On 08/01/2013 01:16 PM, Andrey Ilinykh wrote:
TTL is effectively DELETE; you need to run a repair once every
gc_grace_seconds. If you don't, data might un-delete itself.
How is it possible? Every replica has TTL, so it when it expires every
replica has tombstone. I don't see how you can get data with no
tombstone. What do I miss?
The only way I can think of is this scenario:
- value "A" for some key is written with ttl=30days, to all
replicas (i.e a long ttl or no ttl at all)
- value "B" for the same key is written with ttl=1day, but doesn't
reach all replicas
- one day passes and the ttl=1day values turn into deletes
- gc_grace passes and the tombstones are purged
at this point, the replica that didn't get the ttl=1day value will think
the older value "A" is live.
I'm no expert on this so I may be mistaken, but in any case it's a
corner case as overwriting columns with shorter ttls would be unusual.
- Erik -
