During forwarding of CQL EXECUTE requests, the target node may
not have the prepared statement in its cache. If we do have this
statement as a coordinator, instead of returning PREPARED NOT FOUND
to the client, we want to prepare the statement ourselves on target
node.
For that, we add a new FORWARD_CQL_PREPARE RPC. We use the new RPC
after gettting the prepared_not_found status during forwarding. When
we try to forward a request, we always have the query string (we
decide whether to forward based on this query), so we can always use
the new RPC when getting the prepared_not_found status.
After receiving the response, we try forwarding the EXECUTE request
again.
Add the infrastructure for forwarding CQL requests to other nodes.
When a process() call results in a node bounce (as opposed to a shard
bounce), the coordinator serializes the request and sends it via the
FORWARD_CQL_EXECUTE RPC verb to the target node.
In this patch we omit several features that allow handling more
scenarios that can happen when trying to forward a CQL request,
but the RPC request and response are already prepared for them.
They will be handled in the following commits.
