New Features

• metadata: stabilize ValueFromIncomingContext (#7368)
  • Special Thanks: @KarthikReddyPuli
• client: stabilize the WaitForStateChange and GetState methods, which were previously experimental. (#7425)
• xds: Implement ADS flow control mechanism (#7458)
  • See https://github.com/grpc/grpc/issues/34099 for context.
• balancer/rls: Add metrics for data cache and picker internals (#7484, #7495)
• xds: LRS load reports now include the total_issued_requests field. (#7544)

Bug Fixes

• grpc: Clients now return status code INTERNAL instead of UNIMPLEMENTED when the server uses an unsupported compressor. This is consistent with the gRPC compression spec. (#7461)
  • Special Thanks: @Gayathri625
• transport: Fix a bug which could result in writes busy looping when the underlying conn.Write returns errors (#7394)
  • Special Thanks: @veshij
• client: fix race that could lead to orphaned connections and associated resources. (#7390)
• xds: use locality from the connected address for load reporting with pick_first (#7378)
  • without this fix, if a priority contains multiple localities with pick_first, load was reported for the wrong locality
• client: prevent hanging during ClientConn.Close() when the network is unreachable (#7540)

Performance Improvements

• transport: double buffering is avoided when using an http connect proxy and the target server waits for client to send the first message. (#7424)
• codec: Implement a new Codec which uses buffer recycling for encoded message (#7356)
  • introduce a mem package to facilitate buffer reuse (#7432)
  • Special Thanks: @PapaCharlie