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Comment by skyde | Hacker News Reader

I could not find a description of the algorithm used for distributed transaction. I can only assume it's similar to CockroachDB but looking at the code I see a lot of reference to "LOCK" in the protocol buffer definition which mean they might be using something else.

Anybody know where I can find more documentation ?

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Says they are using Raft: https://raft.github.io/

Raft is a replication protocol which is responsible for the consistency of multiple copies of the same data but it isn't applicable when the data is sharded.

You can use raft as to synchronizing other data structures. If this a KV store then that's as easy as key level locks / ownership / placement.

Raft is used to Replicate write in a shard but distributed transaction is used to make transaction that span several shard atomic (ACID). I could find the implementation at : https://github.com/pingcap/tikv/blob/master/src/storage/mvcc... But a lot of the detail are not clear.

The transaction model is similar to Google's Percolator, and with some performance improvements.

Thanks after seeing its based on themis code that is itself based on Percolator the distributed transaction logic make sense. Any idea how it compare to CockroachDB ?

In CockroachDB using SSI isolation if a Writer encounters a more recently read key the writer transaction restart. This guarantee that Write Skew cannot happen.

In percolator design only allow for SI isolation unless lock are taken while reading.

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