This is mainly useful when we do a rolling restart. This will decrease the load on the master and the network load.
Note that a region is not immediately opened after a close. So:
- it seems preferable to wait before retrying on the other server. An optimisation would be to have an heuristic depending on when the region was closed.
- during a rolling restart, the server moves the regions then stops. So we may have failures when the server is stopped, and this patch won't help.
The implementation in the first patch does:
- on the region move, there is an added parameter on the regionserver#close to say where we are sending the region
- the regionserver keeps a list of what was moved. Each entry is kept 100 seconds.
- the regionserver sends a specific exception when it receives a query on a moved region. This exception contains the new address.
- the client analyses the exeptions and update its cache accordingly...