Changes made to both components:
1. Logs are always flushed on process exit
2. Informer cache sync can no longer hang process start up forever
Changes made to concierge:
1. Add pre-shutdown hook that waits for controllers to exit cleanly
2. Informer caches are synced in post-start hook
Changes made to supervisor:
1. Add shutdown code that waits for controllers to exit cleanly
2. Add shutdown code that waits for active connections to become idle
Waiting for controllers to exit cleanly is critical as this allows
the leader election logic to release the lock on exit. This reduces
the time needed for the next leader to be elected.
Signed-off-by: Monis Khan <mok@vmware.com>
OpenShift has good defaults for these duration fields that we can
use instead of coming up with them ourselves:
e14e06ba8d/pkg/config/leaderelection/leaderelection.go (L87-L109)
Copied here for easy future reference:
// We want to be able to tolerate 60s of kube-apiserver disruption without causing pod restarts.
// We want the graceful lease re-acquisition fairly quick to avoid waits on new deployments and other rollouts.
// We want a single set of guidance for nearly every lease in openshift. If you're special, we'll let you know.
// 1. clock skew tolerance is leaseDuration-renewDeadline == 30s
// 2. kube-apiserver downtime tolerance is == 78s
// lastRetry=floor(renewDeadline/retryPeriod)*retryPeriod == 104
// downtimeTolerance = lastRetry-retryPeriod == 78s
// 3. worst non-graceful lease acquisition is leaseDuration+retryPeriod == 163s
// 4. worst graceful lease acquisition is retryPeriod == 26s
if ret.LeaseDuration.Duration == 0 {
ret.LeaseDuration.Duration = 137 * time.Second
}
if ret.RenewDeadline.Duration == 0 {
// this gives 107/26=4 retries and allows for 137-107=30 seconds of clock skew
// if the kube-apiserver is unavailable for 60s starting just before t=26 (the first renew),
// then we will retry on 26s intervals until t=104 (kube-apiserver came back up at 86), and there will
// be 33 seconds of extra time before the lease is lost.
ret.RenewDeadline.Duration = 107 * time.Second
}
if ret.RetryPeriod.Duration == 0 {
ret.RetryPeriod.Duration = 26 * time.Second
}
Signed-off-by: Monis Khan <mok@vmware.com>
This change fixes a small race condition that occurred when the
current leader failed to renew its lease. Before this change, the
leader would first release the lease via the Kube API and then would
update its in-memory status to reflect that change. Now those
events occur in the reverse (i.e. correct) order.
Signed-off-by: Monis Khan <mok@vmware.com>
