https://github.com/mongodb/specifications/blob/master/source/server-discovery-and-monitoring/server-discovery-and-monitoring.rst#requesting-an-immediate-check

Currently when there is a retryable error, for example, the cluster is scanned synchronously on the main thread. This is the same behavior that was eliminated in RUBY-1357 during client construction and suffers from the same problems:

• Rescan is done on all servers, main thread is blocked while each server is queried even though topology may already have identified a writable server.
• Servers are scanned sequentially.
• There is no time bound on the rescan.

A solution similar to RUBY-1357 needs to be implemented for all of the other rescans. One way to do this I imagine is to request an immediate server recheck for all servers and then wait up to server selection timeout to obtain a usable server.

One difficulty here is the monitor thread is currently not designed to be interruptible - it unconditionally sleeps for the heartbeat interval time. This will need to be changed.

Pseudocode in the spec: https://github.com/mongodb/specifications/blob/master/source/server-discovery-and-monitoring/server-discovery-and-monitoring.rst#monitor-thread