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From Lior Golan <>
Subject RE: Using Cassandra for transaction logging, good idea?
Date Sun, 31 Jul 2011 20:19:38 GMT
How about using Snowflake to generate the transaction ids:

From: Kent Narling []
Sent: Thursday, July 28, 2011 5:46 PM
Subject: Using Cassandra for transaction logging, good idea?


I am considering to use cassandra for clustered transaction logging in a project.

What I need are in principal 3 functions:

1 - Log transaction with a unique (but possibly non-sequential) id
2 - Fetch transaction with a specific id
3 - Fetch X new transactions "after" a specific cursor/transaction
     This function must be guaranteed to:
     A, eventually return all known transactions
     B, Not return the same transaction more than once
     The order of the transactions fetches does not have to be strictly time-sorted
     but in practice it probably has to be based on some time-oriented order to be able to
support cursors.

I can see that 1 & 2 are trivial to solve in Cassandra, but is there any elegant way to
solve 3?
Since there might be multiple nodes logging transactions, their clocks might not be perfectly
synchronized (to millisec level) etc so sorting on time is not stable.
Possibly creating a synchronized incremental id might be one option but that could create
a cluster bottleneck etc?

Another alternative might be to use cassandra for 1 & 2 and then store an ordered list
of id:s in a standard DB. This might be a reasonable compromise since 3 is less critical from
a HA point of view, but maybe someone can point me to a more elegant solution using Cassandra?
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