Adds a user-configurable rate limiter to proxycfg snapshot delivery,
with a default limit of 250 updates per second.
This addresses a problem observed in our load testing of Consul
Dataplane where updating a "global" resource such as a wildcard
intention or the proxy-defaults config entry could starve the Raft or
Memberlist goroutines of CPU time, causing general cluster instability.
Replaces the reflection-based implementation of proxycfg's
ConfigSnapshot.Clone with code generated by deep-copy.
While load testing server-based xDS (for consul-dataplane) we discovered
this method is extremely expensive. The ConfigSnapshot struct, directly
or indirectly, contains a copy of many of the structs in the agent/structs
package, which creates a large graph for copystructure.Copy to traverse
at runtime, on every proxy reconfiguration.
When peering through mesh gateways we expect outbound dials to peer
servers to flow through the local mesh gateway addresses.
Now when establishing a peering we get a list of dial addresses as a
ring buffer that includes local mesh gateway addresses if the local DC
is configured to peer through mesh gateways. The ring buffer includes
the mesh gateway addresses first, but also includes the remote server
addresses as a fallback.
This fallback is present because it's possible that direct egress from
the servers may be allowed. If not allowed then the leader will cycle
back to a mesh gateway address through the ring.
When attempting to dial the remote servers we retry up to a fixed
timeout. If using mesh gateways we also have an initial wait in
order to allow for the mesh gateways to configure themselves.
Note that if we encounter a permission denied error we do not retry
since that error indicates that the secret in the peering token is
invalid.
David Yu