Automatic merge from submit-queue (batch tested with PRs 45953, 45889)
Add /metrics and profiling handlers to kube-proxy
Also expose "syncProxyRules latency" as a prometheus metrics.
Fix https://github.com/kubernetes/kubernetes/issues/45876
The existing healthcheck lib was pretty complicated and was hiding some
bugs (like the count always being 1), This is a reboot of the interface
and implementation to be significantly simpler and better tested.
This changes the userspace proxy so that it cleans up its conntrack
settings when a service is removed (as the iptables proxy already
does). This could theoretically cause problems when a UDP service
as deleted and recreated quickly (with the same IP address). As
long as packets from the same UDP source IP and port were going to
the same destination IP and port, the the conntrack would apply and
the packets would be sent to the old destination.
This is astronomically unlikely if you did not specify the IP address
to use in the service, and even then, only happens with an "established"
UDP connection. However, in cases where a service could be "switched"
between using the iptables proxy and the userspace proxy, this case
becomes much more frequent.
This is a weird function, but I didn't want to change any semantics
until the tests are in place. Testing exposed one bug where stale
connections of renamed ports were not marked stale.
There are other things that seem wrong here, more will follow.
