Hyperdex (http://hyperdex.com/) needs a feature we don't currently support: iterating through the log. We would export LSNs as a string through this interface:

  // Return an opaque timestamp that identifies the current point in time of the
  // database.  This timestamp may be subsequently presented to the
  // NewReplayIterator method to create a ReplayIterator.
  virtual void GetReplayTimestamp(std::string* timestamp) = 0;

Then this interface gets a simplified log cursor:

  // Release a previously allocated replay iterator.
  virtual void ReleaseReplayIterator(ReplayIterator* iter) = 0;

ReplayIterators just return each key/value pair in the log after the starting LSN, with a way to distinguish puts from removes.

@sueloverso, can you please take a look at the best way to implement this down in the log layer?

I think the implementation of ReplayIterator can keep an LSN that increases as each log record is returned, and it can crack open the log record to return the key/value pairs.

Thanks!