New connections can race with GracefulStop such that the server will accept the connection, but then close it immediately. If a connection is accepted before GracefulStop has a chance to effectively cancel the listeners, the server should handle it to avoid client errors.
The parent ClientConn should re-resolve when grpclb loses connection to the
remote balancer.
When the ClientConn inside grpclb gets a TransientFailure, it calls
lbManualResolver.ResolveNow(), which calls parent ClientConn's ResolveNow, and
eventually results in re-resolve happening in parent ClientConn's resolver (DNS
for example).
This PR adds a method to balancer.ClientConn interface, so balancer can tell
parent ClientConn to re-resolve.
WithBalancerName dial option specifies the name of the balancer to be used by the ClientConn. Service config updates can NOT override the balancer option.
1. Call transport Close if newHTTP2Server returns non-nil error.
Handle ConnBegin was called before this error, and handle ConnEnd is not called (because Close() is not called), which caused ConnStats check to fail.
2. Skip stats test in go1.6.
go1.6 doesn't have DialContext (we use Dialer(Cancel: ctx.Done()) instead). When the give context is canceled, this function sometimes returns canceled error, while the server side still gets the conn. This caused the server blocking on reading the preface (which will eventually timeout, but the tests are too short for that), and there will be a missing ConnEnd.
"go1.6, !go1.8" constraints are interpreted as (version >= 1.6 AND ) OR version < 1.8, where (version >= 1.6 AND ) is always false,
so it matches all go versions before 1.8, not only 1.6 and 1.7.
Removed a space, so the constraints are now matches only go1.6 and go1.7 versions
Split round_robin balancer into a base balancer (which manages SubConn and connectivity states), and a round_robin picker.
A custom picker with other picking algorithms can be provided to build custom balancers.
