DAOS-19284 vos: check conflict among distributed transactions - b28 - #18843
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Ticket title is 'daos_test/dfs.py:DaosCoreTestDfs.test_daos_dfs_parallel - Failed concurrent rmdir' |
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Test stage Functional Hardware Medium MD on SSD completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-18843/2/testReport/ |
For a distributed transaction, its epoch is generated by the first accessed server. So two distributed transactions may use the same epoch (if their first accessed servers are different) to operate the same set of object(s) by race. In theory, two read distributed transactions do not conflict with each other, but read maybe just part of the transaction, and there maybe update/punch in the same distributed transaction subsequently. Since we can keep only one (sponsor) timestamp for one TS entry, then have to request another one to restart. That may cause some fake conflict, but correctness is more important and such race is rare. Signed-off-by: Fan Yong <fan.yong@hpe.com>
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Quickly checked as it is a clean cherry-pick from what I have seen.
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For a distributed transaction, its epoch is generated by the first accessed server. So two distributed transactions may use the same epoch (if their first accessed servers are different) to operate the same set of object(s) by race. In theory, two read distributed transactions do not conflict with each other, but read maybe just part of the transaction, and there maybe update/punch in the same distributed transaction subsequently. Since we can keep only one (sponsor) timestamp for one TS entry, then have to request another one to restart. That may cause some fake conflict, but correctness is more important and such race is rare.
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