- we put the query into the execution pool.
- after x ms, if we don't have a result, we add the queries for the secondary replicas
- we take the first answer
- when done, we cancel what's left. Cancelling means:
- removing from the pool if the actual call was not started
- interrupting the call if it has started
Client side, we need to take into account
- a call is not executed immediately after being put into the pool
- a call is a thread. Let's not multiply the number of thread by the number of replicas.
Server side, if we can cancel when it's still in the handler pool, it's much better, as a call
can take some i/o.
Globally, the number of retries, timeout and so on still applies, but it's per replica,
not global. We continue until all retries are done, or all timeouts are exceeded.