Read-Your-Writes (Session Guarantee) RYW
Read-your-writes (a.k.a. read-my-writes) session guarantee of Terry et al. (PDIS 1994): a read carried out on behalf of a session only reflects a state that has already applied all writes previously issued in that same session. On its own it is one of the four session guarantees. Brzezinski et al. (2003) proved PRAM consistency holds iff a system provides read-your-writes together with monotonic reads and monotonic writes (Viotti & Vukolić 2016, Eq. 20), so read-your-writes alone is strictly weaker than PRAM.
Properties
Property vector author-extrapolated — set only where the model’s definition pins the cell down (unknown cells are omitted); cells citing a specific source are marked.
- Reasoning guarantees
- no Coherence
- Atomicity guarantees
- no Multicopy atomic
Ordering relationships
- Strictly weaker than
- PRAM (Pipelined RAM) Consistency — Brzezinski et al. (2003) proved PRAM consistency holds iff a system provides read-your-writes, monotonic reads and monotonic writes (Viotti & Vukolić 2016, Eq. 20). PRAM is the conjunction of the three, so it implies read-your-writes while the converse fails: read-your-writes is strictly weaker than PRAM.
References
- Douglas B. Terry, Alan J. Demers, Karin Petersen, Mike Spreitzer, Marvin Theimer, Brent B. Welch. Session Guarantees for Weakly Consistent Replicated Data. Parallel and Distributed Information Systems (PDIS), 1994. doi:10.1109/PDIS.1994.331722
- Jerzy Brzezinski, Cezary Sobaniec, Dariusz Wawrzyniak. Session Guarantees to Achieve PRAM Consistency of Replicated Shared Objects. Parallel Processing and Applied Mathematics (PPAM), LNCS 3019, 2003. doi:10.1007/978-3-540-24669-5_1
- Paolo Viotti, Marko Vukolić. Consistency in Non-Transactional Distributed Storage Systems. ACM Computing Surveys 49(1), 2016. doi:10.1145/2926965