Behavior Changes

xds: Remove support for GRPC_EXPERIMENTAL_XDS_FALLBACK environment variable. Fallback support can no longer be disabled. (#8482)
stats: Introduce DelayedPickComplete event, a type alias of PickerUpdated. (#8465)
- This (combined) event will now be emitted only once per call, when a transport is successfully selected for the attempt.
- OpenTelemetry metrics will no longer have multiple "Delayed LB pick complete" events in Go, matching other gRPC languages.
- A future release will delete the PickerUpdated symbol.
credentials: Properly apply grpc.WithAuthority as the highest-priority option for setting authority, above the setting in the credentials themselves. (#8488)
- Now that this WithAuthority is available, the credentials should not be used to override the authority.
round_robin: Randomize the order in which addresses are connected to in order to spread out initial RPC load between clients. (#8438)
server: Return status code INTERNAL when a client sends more than one request in unary and server streaming RPC. (#8385)
- This is a behavior change but also a bug fix to bring gRPC-Go in line with the gRPC spec.

New Features

dns: Add an environment variable (GRPC_ENABLE_TXT_SERVICE_CONFIG) to provide a way to disable TXT lookups in the DNS resolver (by setting it to false). By default, TXT lookups are enabled, as they were previously. (#8377)

xds: Fix regression preventing empty node IDs in xDS bootstrap configuration. (#8476)
- Special Thanks: @davinci26
xds: Fix possible panic when certain invalid resources are encountered. (#8412)
- Special Thanks: @wooffie
xdsclient: Fix a rare panic caused by processing a response from a closed server. (#8389)
stats: Fix metric unit formatting by enclosing non-standard units like call and endpoint in curly braces to comply with UCUM and gRPC OpenTelemetry guidelines. (#8481)
xds: Fix possible panic when clusters are removed from the xds configuration. (#8428)
xdsclient: Fix a race causing "resource doesn not exist" when rapidly subscribing and unsubscribing to the same resource. (#8369)
client: When determining the authority, properly percent-encode (if needed, which is unlikely) when the target string omits the hostname and only specifies a port (grpc.NewClient(":<port-number-or-name>")). (#8488)