Google default creds is a combo of ALTS, TLS and OAuth2. The right set of creds will be picked to use based on environment.
This PR contains:
- A new `creds.Bundle` type
- changes to use it in ClientConn and transport
- dial option to set the bundle for a ClientConn
- balancer options and NewSubConnOption to set it for SubConn
- Google default creds implementation by @cesarghali
- grpclb changes to use different creds mode for different servers
- interop client changes for google default creds testing
Fixes https://github.com/grpc/grpc-go/issues/2161
I introduced `serverTerminatedConnectionErr `, because I wanted `callRemoteBalancer` to still returns error on a terminated connections. Its client, which is function `watchRemoteBalancer` can decide how to log this error.
When remote grpclb-server terminates the connection, don't log it as
error. Instead, log it as info.
It is natural for servers to terminate long lived grpc streaming
connections. Two sample reasons to do this are: load balancing and
deployment of a new version. Therefore client of grpclb-server shouldn't
recognise this situation as an error.
This PR splits out grpclb from grpc. I have made the PR in several commits so you can see more clearly the steps that happened.
There are a few possibly contentious points that I would like to make clear up front:
* grpclb will no longer autoload as a load balancer. I think this is okay, as service config is not widely (at all?) used, and I believe this is the only way to access it.
* `internal` is used more, as a way of having code shared between packages without exposing types
* ConnectivityStateEvaluator, as used by grpclb, is no longer thread safe. I believe there is an outer mutex that guards access, but I want to point out this subtle change up here.
All but one tests pass with this, due to another cyclic dependency. I can fix this, but it is a little more widely scoped (such as exposing grpc.server and grpc.errorDesc in the internal package). This PR is a nearly-passing sample of that last step to get this working.
PTAL @menghanl @dfawley
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.
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.
Doug Fawley