### Motivation

use the correct error for the log.

…load balance (#565)

### Motivation

Currently, we are using the server address as the key to do rebalance.
That will be triggered if the user only changes the public address of
the server.
We can use the internal address as the unique identification for the
user to allow the user to change the public address or other information
without the node swapping.


### Modification

- Introduce `ServerContext` struct as the map value.
- Use the internal address as the filter key.