Behavior Changes

• stats/otel: The grpc.lb.pick_first.* metrics have been removed and replaced with grpc.subchannel.* metrics. See gRFC A94 for more details. (#9215)

New Features

• xds: Add support for contains_match in route header matchers. (#9223)
  • Special Thanks: @nvxbug

Bug Fixes

• client: Fix a bug where a ClientConn could get permanently stuck in IDLE when an RPC was canceled during stream creation. Previously, such cancellations triggered stream cleanup twice, corrupting the channel's idleness state and causing subsequent RPCs to fail with deadline exceeded errors. (#9191)
  • Special Thanks: @utkuozdemir
• client: Fix a bug where non-gRPC HTTP responses ending with an empty DATA frame failed the RPC with status code Internal instead of preserving the HTTP-mapped status code and response body. (#9217)
  • Special Thanks: @chengxilo
• credentials: Validate metadata returned by per-RPC credentials, failing the RPC with status code Internal if invalid keys or values are found. Previously, invalid metadata from credentials was sent to the server in outgoing HTTP/2 requests. (#9202)
  • Special Thanks: @buger
• credentials/sts: Prevent potential token leakage by disallowing HTTP redirects during STS token exchange. Previously, 3xx redirects were followed automatically, replaying the request body containing authentication tokens to the redirect destination. (#9299)
  • Special Thanks: @nvxbug
• randomsubsetting: Ignore endpoints that contain no addresses. Previously, this could cause the policy to panic while computing hashes. (#9259)
  • Special Thanks: @fallintoplace
• stats/otel: Ensure method names are populated in trace spans when metrics are disabled. Previously, running with tracing enabled and metrics disabled resulted in server trace spans lacking the RPC method name (recording only "Recv."). (#9262)
• transport: Return io.ErrUnexpectedEOF when EOF is encountered after partial header or message body reads. Previously, partial reads could return a plain io.EOF, failing to distinguish truncated data from a clean end of stream. (#9204)
  • Special Thanks: @buger
• transport: Validate metadata supplied by balancers (in PickResult.Metadata) and resolver addresses, failing the RPC with status code Internal if invalid keys or values are found. Previously, invalid metadata from these sources was sent to the server in outgoing HTTP/2 requests. (#9203)
  • Special Thanks: @buger
• xds: Fix a rare corner case that could prevent a cluster from being removed when it is no longer in use. (#9140)
• xds: Fix panic during route matching for routes containing header matchers with empty exact_match strings. (#9223)
  • Special Thanks: @nvxbug
• xds: Reject routes containing header matchers with empty prefix_match or suffix_match strings. Previously, this caused a panic during route matching. (#9223)
  • Special Thanks: @nvxbug
• xds: Fix EDS drop policies being applied at a much lower rate than configured due to an integer overflow. (#9257)
  • Special Thanks: @nvxbug
• xds: Reject EDS resources containing drop policies with unsupported denominators. Previously, such resources caused the client to panic when calculating drop rates. (#9218)
  • Special Thanks: @nvxbug
• xds/rbac: Reject RBAC configurations containing nested Principal or Permission rules with :scheme or grpc- prefixed header matchers. Previously, such configurations could cause DENY policies to fail open. (#9258)
  • Special Thanks: @nvxbug
• xds/rbac: Rewrite host header matchers to :authority in nested Principal and Permission rules. Previously, this rewrite only applied to top-level rules, causing nested host matchers to never match incoming requests and DENY policies to fail open. (#9258)
  • Special Thanks: @nvxbug
• xds/rbac: Reject CidrRanges with an unset prefix length. Previously, an omitted prefix_len field caused a panic during RBAC configuration parsing. (#9250)
  • Special Thanks: @nvxbug

Performance Improvements

• transport: Avoid a heap allocation when flushing shared write buffers. (#9233)
  • Special Thanks: @zaidoon1
• credentials/alts: Support dynamic frame size negotiation and add the GRPC_GO_EXPERIMENTAL_ALTS_MAX_FRAME_SIZE environment variable (default 4KiB, max 512KiB) to configure the maximum ALTS record frame size. (#9268)