We're considering switching from using Redis to Cassandra to store
short lived (~1 hour) session tokens, in order to reduce the number of
data storage engines we have to manage.
Can anyone foresee any problems with the following approach:
1) Use the TTL functionality in Cassandra to remove old tokens.
2) Store the tokens in a table like:
CREATE TABLE tokens (
id uuid,
username text,
// (other session information)
PRIMARY KEY (id)
);
3) Perform ~100 writes/sec like:
INSERT INTO tokens (id, username )
VALUES (468e0d69-1ebe-4477-8565-00a4cb6fa9f2, 'bob')
USING TTL 3600;
4) Perform ~1000 reads/sec like:
SELECT * FROM tokens
WHERE ID=468e0d69-1ebe-4477-8565-00a4cb6fa9f2 ;
The tokens will be about 100 bytes each, and we will grant 100 per
second on a small 3 node cluster. Therefore there will be about 360k
tokens alive at any time, with a total size of 36MB before database
overhead.
My biggest worry at the moment is that this kind of workload will
stress compaction in an unusual way. Are there any metrics I should
keep an eye on to make sure it is working fine?
I read over the following links, but they mostly talk about DELETE-ing
and tombstones. Am I right in thinking that as soon as a node performs
a compaction then the rows with an expired TTL will be thrown away,
regardless of gc_grace_seconds?
https://issues.apache.org/jira/browse/CASSANDRA-7534
http://www.datastax.com/dev/blog/cassandra-anti-patterns-queues-and-queue-like-datasets
https://issues.apache.org/jira/browse/CASSANDRA-6654
Thank you
Phil
