Transactions across cache regions

Question

Hello,
Can a single unit of work (/transaction) be guaranteed to co-ordinate across multiple cache regions (both with and without a CacheStore plugged into the nodes)?

Answer 1

Hi good stuff,
it depends on what you mean transactions.
Coherence transactions (both via the local transaction API and the Cache Adapters) are available to gather operations on one more caches together, to provide isolation of such transactions from one another with locking and version checking and commit changes to the cache conditionally, subject to version checking).
However, such operations are NOT atomically rolled back in case an exception was thrown during serialization or from a cache store.
So provided that your serialization/deserialization code is error-free, and you don't use synchronous writes or removes on cache-stores (write-through operations), then yes, such transactions would succeed or would fail atomically in the prepare phase (due to version checking detecting version mismatch).
However, in case write-through cache stores are used, it is not guaranteed that the outcome would be an atomic success or atomic rollback, as each cache-store operation is a separate backend transaction on its own, and failure in the writing of a later entry cannot rollback an already committed write from an earlier processed entry, or an entry successfully written on another cache node.
In case write-behind, the resulting writes due to the put operations are delayed, so failure in those are not thrown back to the client (the transaction). The remove operations are handled synchronously, but I am not sure if failure in those are thrown back to the client. My guess would be that they are not, considering that failures in other operations in write-behind are NOT thrown back to the client. In case of failures of operations not thrown back to the client, from the point of the client transaction Coherence behaves as if no cache stores were used at all.
Best regards,
Robert