This version adds support for tailing TokuMX, which uses a different oplog format from Mongo, separating the concepts of time and ordering of oplog entries. This sadly breaks most applications currently using mongoriver and will require invasive changes to persistant tailers.
More specifically - TokuMX uses BSON::Binary instead of BSON::Timestamp for keeping track of the database oplog position.
Tailers gained a few new methods: database_type either returns :toku or :mongo based on which type of database is connected to the tailer.
Tailers also have a most_recent_position method, which returns the most recent oplog position in the database. It has an optional before_time parameter of type Time, which if passed, finds the latest position before (or at) that time. It is useful for converting timestamps to positions to tail from in tailers.
In persistent tailers, the read_timestamp and write_timestamp methods were replaced with read_state and write_state, which read/write state hashes from/to the database. read_state should return nil if not state has been stored in the database yet.
In addition, there are convenience methods read_timestamp and read_position (already implemented) which extract the appropriate field from the read_state results. Both will return nil if read_state returns nil.
State hashes have two fields - 'time' which is a ruby Time object (used for humans, logs) and 'position' of type BSON::Binary or BSON::Timestamp which the tailer uses to keep track of its position.
Persistent tailers need to define both read_state and write_state methods, which deserialize and serialize state hashes according to the database type.
Also, calls to read_timestamp and other methods mentioned above will have to be updated.
Also, if your application has custom filters for namespaces or other things tokumx has updated, those need to be updated.
Note that to do seamless upgrades, some more mangling might be needed (e.g. updating database tables, figuring out how to get the position from an existing timestamp). The following file should be a good example of what this might entail: https://github.com/stripe/mosql/blob/karl-mongoriver-support-for-tokumx/lib/mosql/tailer.rb