In very rare cases, we could start an RPC before the picker had been updated to
one that would return a valid SubConn. This is not a problem as the new picker
will be called again as soon as it is updated, but it can lead to test flakes
that depend upon the picker not being called before being ready.
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
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.
Remove some log messages from balancer_conn_wrappers and
balancer_v1_wrapper which seem to be indented for debugging (one of them
was even logging a pointer address).
They can produce a lot of log messages which don't add value in a normal
scenario.
