This PR:
- moves wrapping of appliers (due to Alarms) out of server.go into uber_applier.go
- clearly devides the application logic into: chain of:
a) 'WrapApply' (generic logic across all the methods)
b) dispatcher (translation of Apply into specific method like 'Put')
c) chain of 'wrappers' of the specific methods (like Put).
- when we do recovery (restore from snapshot) we create new instance of appliers.
The purpose is to make sure we control all the depencies of the apply process, i.e.
we can supply e.g. special instance of 'backend' to the application logic.
The PR removes calls to applierV3base logic from server.go that is NOT part of 'application'.
The original idea was that read-only transaction and Range call shared logic with Apply,
so they can call appliers directly (but bypassing all 'corrupt', 'quota' and 'auth' wrappers).
This PR moves all the logic to a separate file (that later can become package on its own).
Usually the consistent_index should be greater than the index of the
latest snapshot with suffix .snap. But for the snapshot coming from the
leader, the consistent_index should be equal to the snapshot index.
When clients have no permission to perform whatever operation, then
the applying may fail. We should also move consistent_index forward
in this case, otherwise the consitent_index may smaller than the
snapshot index.
When etcdserver receives a LeaseRenew request, it may be still in
progress of processing the LeaseGrantRequest on exact the same
leaseID. Accordingly it may return a TTL=0 to client due to the
leaseID not found error. So the leader should wait for the appliedID
to be available before processing client requests.
humanize.Time() drops precision resulting in some events reporting they took
"now" time to complete. Using time.Duration.String() results in accurate
duration being reported.
Fixes#13905
Reason to store CI and term in backend was to make db fully independent
snapshot, it was never meant to interfere with apply logic. Skip of CI
was introduced for v2->v3 migration where we wanted to prevent it from
decreasing when replaying wal in
https://github.com/etcd-io/etcd/pull/5391. By mistake it was added to
apply flow during refactor in
https://github.com/etcd-io/etcd/pull/12855#commitcomment-70713670.
Consistency index and term should only be negotiated and used by raft to make
decisions. Their values should only driven by raft state machine and
backend should only be responsible for storing them.
