Azure-docs: Clarification of if-match ETag condition

[nabeelsul]

The documentation seems to indicate so, but just to be completely clear: If multiple writers use the "if-match" ETag condition, it is guaranteed that only one of those writes will succeed, regardless of the region, geographic settings, or consistency level of the CosmosDB instance?

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• ID: 58a1f8fb-77e3-acac-eb1e-05571fc4e018
• Version Independent ID: 4bd2399c-7298-848d-e04d-88b74b132dde
• Content: Database transactions and optimistic concurrency control in Azure Cosmos DB
• Content Source: articles/cosmos-db/database-transactions-optimistic-concurrency.md
• Service: cosmos-db
• GitHub Login: @markjbrown
• Microsoft Alias: mjbrown

[NavtejSaini-MSFT]

@nabeelsul We are checking this and will get back to you.

[NavtejSaini-MSFT]

@nabeelsul We are assigning this to our author for further review.
@markjbrown @SnehaGunda Please check the users questions and help regarding the same.

[markjbrown]

Thanks for the question.

For a single-master scenario where multiple users are updating the same replica set this is correct. The commit happens within a replica set for each partition using snap shot isolation. Once the data is committed to three replicas (majority quorum), the etag is updated.

In multi-master scenarios, the same thing happens but in each region if multiple users are updating the same item in different regions. In those scenarios commits happening in different regions will be merged using the conflict resolution policy chosen. In scenarios where no conflict policy is used the item which is committed globally is non-deterministic, with the other commits being written to the conflict feed.

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