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  1. Core Server
  2. SERVER-31715

createIndexes (and dropIndexes) may not create index (or leave index around) if migration happens concurrently

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Details

    • Bug
    • Status: Closed
    • Major - P3
    • Resolution: Gone away
    • 3.6.3
    • None
    • Sharding
    • 15

    Description

      Bug #1: It's possible to get ok:1 from createIndexes, but not have the index propagated to all shards if a migration happens in between the recipient and donor shards processing the createIndexes.

      In this case, the raw response for the createIndex from each shard will contain either CannotImplicitlyCreateCollection or ok:1, and the overall createIndexes command will return ok:1.

      Today, to remedy this, createIndexes can be re-run against against the mongos. This second createIndexes will return ok:1, since createIndexes is idempotent.

      Bug #2: It's possible to get ok:1 from dropIndexes, but have the index get created afterwards on some shard if a migration happens in between the recipient and donor shards processing the dropIndexes.

      In this case, the raw responses for the dropIndex from each shard will contain either NamespaceNotFound or ok:1, and the overall dropIndexes command response will be ok:1.

      Today, to remedy this, dropIndexes can be re-run against the mongos. This second dropIndexes will return ok:0, since dropIndexes is not idempotent, but the index will get dropped from any shards that had the index.

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              backlog-server-sharding Backlog - Sharding Team
              esha.maharishi@mongodb.com Esha Maharishi
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                Created:
                Updated:
                Resolved: