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.
The code now ensures that each of the test is running in its own directory as opposed to shared os.tempdir.
```
$ (cd tests && env go test -timeout=15m --race go.etcd.io/etcd/tests/v3/integration/clientv3/examples -run ExampleAuth)
2022/04/03 10:24:59 Running tests (examples): ...
2022/04/03 10:24:59 the function can be called only in the test context. Was integration.BeforeTest() called ?
2022/04/03 10:24:59 2022-04-03T10:24:59.462+0200 INFO m0 LISTEN GRPC {"member": "m0", "grpcAddr": "localhost:m0", "m.Name": "m0"}
```
Nearly none of the tests was checking the value... just assuming WaitLeader success.
```
maintenance_test.go:277: Waiting for leader...
logger.go:130: 2022-04-03T08:01:09.914+0200 INFO m0 cluster version differs from storage version. {"member": "m0", "cluster-version": "3.6.0", "storage-version": "3.5.0"}
logger.go:130: 2022-04-03T08:01:09.915+0200 WARN m0 leader failed to send out heartbeat on time; took too long, leader is overloaded likely from slow disk {"member": "m0", "to": "2acc3d3b521981", "heartbeat-interval": "10ms", "expected-duration": "20ms", "exceeded-duration": "103.756219ms"}
logger.go:130: 2022-04-03T08:01:09.916+0200 INFO m0 updated storage version {"member": "m0", "new-storage-version": "3.6.0"}
...
logger.go:130: 2022-04-03T08:01:09.926+0200 INFO grpc [[roundrobin] roundrobinPicker: Build called with info: {map[0xc002630ac0:{{unix:localhost:m0 localhost <nil> 0 <nil>}} 0xc002630af0:{{unix:localhost:m1 localhost <nil> 0 <nil>}} 0xc002630b20:{{unix:localhost:m2 localhost <nil> 0 <nil>}}]}]
logger.go:130: 2022-04-03T08:01:09.926+0200 WARN m0 apply request took too long {"member": "m0", "took": "114.661766ms", "expected-duration": "100ms", "prefix": "", "request": "header:<ID:12658633312866157316 > cluster_version_set:<ver:\"3.6.0\" > ", "response": ""}
logger.go:130: 2022-04-03T08:01:09.927+0200 INFO m0 cluster version is updated {"member": "m0", "cluster-version": "3.6"}
logger.go:130: 2022-04-03T08:01:09.955+0200 INFO m2.raft 9f96af25a04e2ec3 [logterm: 2, index: 8, vote: 9903a56eaf96afac] ignored MsgVote from 2acc3d3b521981 [logterm: 2, index: 8] at term 2: lease is not expired (remaining ticks: 10) {"member": "m2"}
logger.go:130: 2022-04-03T08:01:09.955+0200 INFO m0.raft 9903a56eaf96afac [logterm: 2, index: 8, vote: 9903a56eaf96afac] ignored MsgVote from 2acc3d3b521981 [logterm: 2, index: 8] at term 2: lease is not expired (remaining ticks: 5) {"member": "m0"}
logger.go:130: 2022-04-03T08:01:09.955+0200 INFO m0.raft 9903a56eaf96afac [term: 2] received a MsgAppResp message with higher term from 2acc3d3b521981 [term: 3] {"member": "m0"}
logger.go:130: 2022-04-03T08:01:09.955+0200 INFO m0.raft 9903a56eaf96afac became follower at term 3 {"member": "m0"}
logger.go:130: 2022-04-03T08:01:09.955+0200 INFO m0.raft raft.node: 9903a56eaf96afac lost leader 9903a56eaf96afac at term 3 {"member": "m0"}
maintenance_test.go:279: Leader established.
```
Tmp
Currently the discovery url is just one endpoint. But actually it
should be the same as the etcdctl, which means that it should be
a list of endpoints. When one endpoint is down, the clientv3 can
fail over to the next endpoint automatically.
To avoid inconsistant behavior during cluster upgrade we are feature
gating persistance behind cluster version. This should ensure that
all cluster members are upgraded to v3.6 before changing behavior.
To allow backporting this fix to v3.5 we are also introducing flag
--experimental-enable-lease-checkpoint-persist that will allow for
smooth upgrade in v3.5 clusters with this feature enabled.
The io/ioutil package has been deprecated as of Go 1.16, see
https://golang.org/doc/go1.16#ioutil. This commit replaces the existing
io/ioutil functions with their new definitions in io and os packages.
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
