When performing the downgrade operation, users can confirm whether each member
is ready to be downgraded using the field 'storageVersion'. If it's equal to the
'target version' in the downgrade command, then it's ready to be downgraded;
otherwise, the etcd member is still in progress of processing the db file.
The ClientConfig is a fully declarive configuration, so it makes more
sense to rename it to ConfigSpec. It can also mitigate the confusion
between Config and ClientConfig.
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.
The directory created by `T.TempDir()` and is automatically removed when
the test and all its subtests complete.
Reference: https://pkg.go.dev/testing#T.TempDir
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
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.
This is because etcd v3.5 will panic when it encounters
ClusterVersionSet entry with version >3.5.0. For downgrades to v3.5 to
work we need to make sure this entry is snapshotted.
Problem with old code was that during downgrade only members with
downgrade target version were allowed to join. This is unrealistic as
it doesn't handle any members to disconnect/rejoin.
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>
To make it possible to alert on misconfigured etcd clusters that have
missing/superfluous peers, expose the list of peers as a metric.
This metric can, for example, be compared to the control-plane nodes of
a kubernetes cluster.
