Problem Statement/Rationale

The collectionExists variable is populated here

https://github.com/mongodb/mongo-tools/blob/10c7902dc3246abdbadd467777cbe2eb2393ef60/mongorestore/restore.go#L297

And then used here:

https://github.com/mongodb/mongo-tools/blob/10c7902dc3246abdbadd467777cbe2eb2393ef60/mongorestore/restore.go#L369

If a mongodb client creates the collection between the time when it is created and when it is checked, it results in restore failure
 
Failed: mydb.mycollection: error creating collection mydb.mycollection: error running create command: a collection 'mydb.mycollection' already exists

Steps to Reproduce

Use a client that populates data into the collection at regular intervals. Delete the collection and run mongorestore. If executed sufficient number of times, this will hit this error.

Expected Results

This error should be ignored by mongorestore, since the intent is to create the collection anyway.

Actual Results

Restore fails.

Additional Notes