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> Thus far, causal consistency has generally been limited to research projects ... MongoDB is one of the first commercial databases we know of which provides an
by rystsov 8y ago
> Thus far, causal consistency has generally been limited to research projects ... MongoDB is one of the first commercial databases we know of which provides an implementation.
Cosmos DB provides session consistency (looks like an another name for causal consistency) at least since 2014 [1].
Cosmos DB's session guarantees [2]: consistent prefix, monotonic reads, monotonic writes, read-your-writes, write-follows-reads.
Mongo DB's causal consistency guarantees [3]: monotonic reads, monotonic writes, read-your-writes, write-follows-reads.
Doubt that four years later still qualities as one of the first.
[1] https://www.infoq.com/news/2014/08/microsoft-azure-documentdb https://www.infoq.com/news/2014/08/microsoft-azure-documentd...
[2] https://docs.microsoft.com/en-us/azure/cosmos-db/consistency-levels https://docs.microsoft.com/en-us/azure/cosmos-db/consistency...
[3] https://docs.mongodb.com/manual/core/read-isolation-consistency-recency/ https://docs.mongodb.com/manual/core/read-isolation-consiste...
- Strongerpass 8y ago.. but the post didn't say it was first. Not even the part you quoted.
- Boxxed 8y agoWell, the quote you reference says, "one of the first," doesn't it?
- Volt 8y ago"we know of"
- polskibus 8y agoWas Cosmos DB tested by Jepsen?
- rystsov 8y agoIt's off-topic. But yes, Cosmos DB has rigorous tests[1] including Jepsen (a tool). [1] https://twitter.com/dharmashukla/status/869104163510034432 https://twitter.com/dharmashukla/status/869104163510034432
- aphyr 8y agoTo clarify: no, Jepsen, as an organization, has not worked with CosmosDB. I'm delighted they have rigorous tests, and I'm glad our tool has been helpful for them! We just can't say anything about those tests, because we haven't looked yet. Maybe someday!
- namibj 8y agoI understand them having developed TLA+ to guide their design and test consistency primitives.
- aphyr 8y agoCausal and session are definitely similar, but I'm not entirely sure if causal implies consistent prefix, and conversely, I think causal miiight have stronger implications than just the intersection of MR, MW, RYW, and WFR. Because we weren't entirely certain whether we could make that claim regarding Cosmos, we opted to be conservative.
- rystsov 8y agoI agree it's hard for me too to be precise about naming in academic sense. But this published paper "Writes: the dirty secret of causal consistency" says that both Cosmos DB and MongoDB have causal consistency so I don't know.. At least Cosmos DB and MongoDB provide the same guarantees for session/causal.