Ohad Shacham created OMID-58:
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Summary: Snapshot isolation violation in read only transactions
Key: OMID-58
URL: https://issues.apache.org/jira/browse/OMID-58
Project: Apache Omid
Issue Type: Bug
Reporter: Ohad Shacham
Read only transactions in snapshot isolation cannot conflict with any other
transaction. Therefore, the commit process does not contact the TSO and mark
the transaction as committed.
This can cause to snapshot isolation violation in cases where the coprocessor
deletes information from HBase that changes the snapshot of an inflight read
only transaction t. t in this case will be marked as committed, even thought it
did not read a consistent snapshot.
t would be aborted if the commit process would contact the tso because its read
timestamp is smaller than the low water mark.
A solution for this would be to contact the TSO, check the low water mark,
identify in the requestProcessor that the transaction is read only, and
immediately return a result using the reply processor. This will reduce the
latency (v.s. the regular flow) of read only transactions, while maintaining
snapshot isolation.
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