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  1. Documentation
  2. DOCS-13476

Investigate changes in SERVER-46249: Cluster createIndexes and createCollection may fail to run in readConcern-specifying transactions





      Downstream Change Summary

      This will be a known error for PM-1168. Please ensure it is in release notes for 4.4.

      Description of Linked Ticket

      The test concurrent_drops_and_creates.js can be modified to create a scenario where createIndexes and createCollection can fail with the following message:

      "Command create does not support { readConcern: { level: \"snapshot\", provenance: \"clientSupplied\" } } :: caused by :: read concern not supported",

      This failure occurs if concurrent_drops_and_creates.js explicitly creates a collection or an index inside this transaction (instead of the highlighted lines), and is run inside sharded_jscore_txns.

      I spun up a ShardingTest locally and attempted the same sequence of events as this test, but I did not run into the error, which leads me to believe something about the testing configuration results in readConcern getting explicitly forwarded to the cluster create and cluster createIndexes commands.

      Note that this error does not occur when running the same test (with the above modification) in replica_sets_jscore_passthrough.

      As an update, it looks like in order to reproduce this error, createCollection/createIndexes needs to be run after another operation inside a transaction. If either is the first operation inside the transaction, the error does not occur.

      Scope of changes

      Impact to Other Docs

      MVP (Work and Date)

      Resources (Scope or Design Docs, Invision, etc.)




            jeffrey.allen@mongodb.com Jeffrey Allen
            backlog-server-pm Backlog - Core Eng Program Management Team
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              3 years, 34 weeks, 3 days ago