Documentation Request Summary:

This ticket makes shard secondaries participate in the shard versioning protocol. This makes them:
1) return an error for a request from mongos if the mongos's routing table cache is more stale than the secondary's, so that mongos refreshes its cache and re-targets
2) filter results using their (new) routing table cache, so that they don't return oprhaned documents for versioned requests

The following commands were previously unversioned against secondaries, but are now versioned:

• aggregate
• count
• find

The following commands are still unversioned against secondaries, because they were unversioned against primaries:

• geoNear
• distinct

Finally, note that the following commands are not supported on sharded collections:

• group