ReactiveMongo 0.12.7 Fails to create new collection

[ne...@vatbox.com]

When trying to use: 

reactiveMongoApi.database.map(_.collection(collectionName))

Getting:

Error injecting constructor, reactivemongo.api.commands.bson.DefaultBSONCommandError: CommandError[code=26, errmsg=Collection myDb.coll doesn't exist, doc: {
  "ok": NumberDecimal(0.0),
  "errmsg": "Collection myDb.coll doesn't exist",
  "code": 26,
  "codeName": "NamespaceNotFound"
}]

Scala version: "2.12.3"

[Cédric Chantepie]

I guess the collectionName given is "myDb.coll", which is invalid as there is no `myDb` database (not that as DB is already resolved, there is no need to specify it again in the collection name).

[ne...@vatbox.com]

No, the db exists, the collection is new: Tests running with existing collection don't throw this error. Only tests creating new collections on an existing db causes the error. 

[Cédric Chantepie]

As collection resolution is tested from MongoDB 2.6 to 3.4, unless a reproducer is shared, the hypothesis that collectionName is wrong is the only one. Best regards.

[ne...@vatbox.com]

Hi,

Taking a deeper look, the problem is not with creating a new collection, but with ensuring an index.

When a collection doesn't exists - 0.12.7 throws the exception while 0.12.6 creates the index. The mongo-shell behaves as 0.12.6.

This project re-creates the issue: master branch uses 0.12.6 while 12-7 uses 0.12.7 version. Hope you find it helpful.

[Cédric Chantepie]

The behaviour at driver level is not the same at MongoShell level, as MongoShell function/operation doesn't always corresponds to the MongoDB protocol (commands).

There it is the MongoDB server which is refusing to ensure an index on a not existing collection.

[Kailuo Wang]

I confirm this is a behavior change in creating a new index on a new db.collection between 0.12.6 and 0.12.7.

When you call indexesManager.ensure with a db and collection yet to be created, with everything else remains the same,

0.12.6 will create the new db, collection and index,

0.12.7 fails with an error 26, either DB does not exist or collection does not. 

I don't think of it as a bug, just a behavior change. That bein said, I would appreciate a work around, e.g. how can I use reactivemongo to ensure a new db and collection is created before calling this indexesManager.ensure? This is particularly needed when running tests on CI like travis. 
Thanks in advance. 

[Yardena Meymann]

You can use something like:

collection.create().recover {

  case CommandError.Code(48) => () //name exists

} flatmap { _ =>  

  collection.indexManager.ensure(...) 

}

Or optimistically:

collection.indexManager.ensure(...).recoverWith {

  case CommandError.Code(26) => //no collection

    collection.create().recover {

      case CommandError.Code(48) => () //name exists

    } flatmap { _ =>  

      collection.indexManager.ensure(...) 

    }

}

[Kailuo Wang]

Thanks Yardena, that's basically the solution I ended up with. 

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[ne...@vatbox.com]

It turned out that:

1) ensure index was not the problem, but rather the listIndexes() call under ensure function.

2) ensure index is deprecated from mongo 3.0

Easiest solution was to simplify use createIndex instead. 

[James Brems]

Does this issue still exist in reactivemongo 0.16.0 ? 

I just switched to 0.16.0, and I use ensure index also for not existing collections / dbs, and it seems to work quite well.

BR James