This ticket is an extension to
SERVER-18407 to cover custom write concern settings with replica set tags.
SERVER-18407, it is presently possible to create a custom write concern setting using replica set tags that is impossible to be satisfied. For example:
Please note the identical "ssd": "installed" tag defined in the replica set members.
Using this setting, attempts to insert into the collection using the user-defined custom write concern of w: ssdWriteConcern will always fail. The server apparently counts the number of unique values in the associated replica set tags to determine that the write concern was satisfied:
The desired behaviour is to output a similar error message as per
SERVER-18407 if the write concern can never be satisfied given a replica set configuration.