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From Todd Nine <t...@spidertracks.co.nz>
Subject Questions regarding batch mutates and transactions
Date Wed, 26 May 2010 09:45:54 GMT
Hey guys,
  I originally asked this on the Hector group, but no one was sure of the
answer.  Can I get some feedback on this.  I'd prefer to avoid having to use
something like Cages if I can for most of our use cases.  Long term I can
see we'll need to use something like Cages, especially when it comes to
complex operations such as billing.  However for a majority of our uses, I
think it's a bit overkill.  I've used transactions heavily in the workplace
on SQL based app developments.  To be honest, a majority of application's
I've built utilize optimistic locking, and only the atomic, consistent, and
durable functionality of transactional ACID properties.

To encapsulate all 3, I essentially need all writes to cassandra for a given
business invocation to occur in a single write.  With Spring, I would
implement my own transaction manager which simply adds all mutates and
delete ops to a batch mutate.  When my transaction commits, I would execute
the mutation on the given keyspace.  Now this would only work if the
following semantics apply.  I've tried searching for details in Cassandra's
batch mutate, but I'm not finding what I need.  Here are 2 use cases as an
example.

Case 1: Successful update : User adds new contact

Transaction Start.
Biz op 1. Row is created in  "contacts" and all data is added via batch
mutation
Biz op 2. Row is created for an SMS message is created for queueing  through
the SMS gateway
return op 2
return op 1
Transaction Commit (batch mutate executed)

Case 2. Failed update: User adds new contact

Biz op 1. Row is created in "contacts"
Biz op 2. Row is created for SMS message queuing.  Fails due to invalid
international phone number format
return op 2
return op 1
Transaction is rolled back (batch mutate never executed)


Now, here is where I can't find what I need in the doc.  In case 1, if my
mutation from biz op 2 were to fail during a batch mutate operation
encapsulating all mutations, does the batch mutation as a whole not get
executed, or would I still have the mutation from op 1 written to cassandra
while the op 2 write fails?

Thanks,

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