chore(main): release bigtable 1.56.0 - #20464

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1.56.0 (2026-09-03)

Features

• bigtable/accelerator: Add --user-agent flag to daemon (#20341) (6b33c06)
• bigtable/accelerator: Add daemon binary with identity verification (#20330) (2f9cf89)
• bigtable/accelerator: Add proxy channel scaffold owning a sessi… (#20310) (d65ca7d)
• bigtable/accelerator: Add stdin-EOF and parent-PID lifecycle wa… (#20328) (dc1c6ae)
• bigtable/accelerator: Add UDS server with authenticated proxy i… (#20320) (a837020)
• bigtable/accelerator: Add V2-to-session request adapters (#20271) (4cb6f16)
• bigtable/accelerator: Authenticate UDS callers with a stdin tok… (#20324) (7847ab7)
• bigtable/accelerator: Dispatch MutateRow and single-row ReadRow… (#20312) (c89f336)
• bigtable/bttest: Honor the table's timestamp granularity (#20456) (0054866)
• bigtable: Add AFE picker (Simple / LeastInFlight / LeastLatency) (#20204) (bcbf714)
• bigtable: Add ChainInterceptors and RetryingVRpc for vRPC pipeline (#20185) (c7a832a)
• bigtable: Add ClientConfig.DisableSession to opt out of session backend (#20297) (7ee5e44)
• bigtable: Add ClientConfigurationManager (#19986) (3a8f927)
• bigtable: Add debug tag counter (recordDebugTag / assertDebugTag) (#20114) (3c97590)
• bigtable: Add getClientConfigDirectAccessChecker for session pools (#20209) (3b8d30a)
• bigtable: Add lazyPool helper for on-demand session pool opening (#20182) (f6ae3fb)
• bigtable: Add NoOpChannelPrimer for session channel pools (#20208) (d055a8a)
• bigtable: Add opensession descriptors for bigtable (#14647) (8968f4f)
• bigtable: Add PeakEwma continuous time-decay latency tracker (#20187) (9d124ef)
• bigtable: Add per-AFE sessionList for the two-tier session pool (#20224) (dbf0c3f)
• bigtable: Add PoolSizer for server-driven session pool capacity (#20189) (57ebbeb)
• bigtable: Add protoRowToRow conversion helper for TableShim (#20257) (1297143)
• bigtable: Add Session debug surface (observability fields + methods) (#20211) (d8d3e16)
• bigtable: Add Session lifecycle (Start, Close, ForceClose, readLoop, heartBeatLoop) (#20215) (b9e53c6)
• bigtable: Add session package with SessionClient + SessionTableAPI interfaces (#20180) (4b82fd2)
• bigtable: Add Session primitives (AttemptOutcome, vRPC ctx, msgtype) (#20116) (e1011e2)
• bigtable: Add Session state enum (#19981) (0748972)
• bigtable: Add Session struct + state machine (#20117) (09acbb3)
• bigtable: Add session.Config.EnableDebug to gate sessionz debug state (#20247) (ce74c31)
• bigtable: Add SessionClient + SessionTable + lazyPool (#20228) (ab2c96c)
• bigtable: Add SessionPoolImpl (two-tier pool + scaling + debug) (#20225) (683eda8)
• bigtable: Add SessionThrottler / AdaptiveSessionThrottler for OpenSession pacing (#20184) (02e3c6d)
• bigtable: Add SessionThrottler / AdaptiveSessionThrottler for OpenSession pacing (#20184) (29be83e)
• bigtable: Add sessionTracer for per-Session lifecycle + vRPC metrics (#20190) (a466345)
• bigtable: Add traffic diverter and table shim for bigtable (#14633) (2f3c918)
• bigtable: Add virtual RPC descriptors (#14648) (5eedda1)
• bigtable: Debug tags for GetClientConfiguration session_configuration state (#20472) (8e57e4b)
• bigtable: Enable JWT (#19957) (af93528)
• bigtable: Enable new auth library and JWT for instance admin client (#20013) (21c4a44)
• bigtable: Enable new auth library and remove async refresh (#19943) (0d3697b)
• bigtable: Expose a client option to disable direct access: (#14626) (f22b29f)
• bigtable: Generate Admin API client using selective gapic (#19962) (a37509d)
• bigtable: Modularize channel priming behind a ChannelPrimer interface (#20027) (5214ab7)
• bigtable: Modularize Direct Access compatibility check (#19987) (a25e93d)
• bigtable: Refactor channel_pool_factory as we need to maintain two channel factory one for session and another for unary (#14652) (0c0b6ce)
• bigtable: Rename session pool display to <resource-id>-<PERM> (#20248) (35e146e)
• bigtable: Route Client.Open()-returned *Table through the Diverter (#20273) (2b81c7d)
• bigtable: Serve grpc.health.v1.Health from the accelerator daemon (#20446) (5fba38a)
• bigtable: State-based classification for abnormal session close (#20243) (f2905b7)
• bigtable: TableShim fallback to classic on session UNIMPLEMENTED (#20269) (36540af)
• bigtable: TTL-on-idle cache for per-resource session.TableAPI (#20263) (00b2a49)
• bigtable: Update admin.go to support instance edition (#14479) (cf1153d)
• bigtable: Wire Diverter on Client and route Open* via TableShim (#20256) (b32fbd7)
• bigtable: Wrap admin client (#14534) (0bea4ba)
• o11y: Regenerate clients for LRO tracing (#20107) (779074e)
• Update API sources and regenerate (#14701) (a9b7921)
• Update API sources and regenerate (#19950) (c7607be)
• Update API sources and regenerate (#20369) (bfe3aaf)
• Update API sources and regenerate (#20459) (5426e32)
• Update sources and regenerate (#20399) (a6b5cdb)

Bug Fixes

• bigtable/internal/transport: Drop redundant defer p.Close() in AFE picker tests (#20311) (c05b767)
• bigtable: AFE picker latency signal — subtract poolWait and compute TransportLatency = wire − backend at source (#20281) (bb8c4d5)
• bigtable: Default cluster/zone in toOtelMetricAttrs to avoid Monitoring reject (#20178) (14493f4)
• bigtable: Disable connection pooling when emulator is set (#14483) (a07a26b)
• bigtable: Disable dynamic channel pool by default and raise default pool size to 10 (#19945) (5ddf8d4)
• bigtable: Eliminate stats-handler MD race in internal/metrics tracer (#20158) (c387066)
• bigtable: Guard NewStream OnFinish against grpc-go double-fire (#20295) (b51da29)
• bigtable: Measure real scheduling delay in pacemaker_delays (#20445) (e1304d6)
• bigtable: Raise default connection-recycler MaxAge to 7 days (#19940) (a7959ef)
• bigtable: Real per-resource pool teardown on sessionTable.Close + cache close-race gate (#20264) (599aea9)
• bigtable: Register c2p resolver + RLS balancer for accelerator daemon DirectPath (#20362) (95f372f)
• bigtable: Retry unexpected EOF errors (#13157) (2b4ac42)
• bigtable: Scope session pool maintenance loops to the pool, not the client (#20444) (7457e6e)
• bigtable: Session client — set AllowNonDefaultServiceAccount on DirectPath dial (#20343) (b9c76ec)
• bigtable: Session client — single ownership + single-flight pool loading (#20368) (f4ad950)
• bigtable: Session pool — re-drive creation after a never-activated close so the consecutive-failure breaker is reachable (#20355) (ee74949)
• bigtable: Session.durations / session.uptime — set explicit histogram bucket boundaries (#20276) (97eee22)
• bigtable: SessionTableHandle self-heals across cache eviction (#20296) (0dd98cd)
• bigtable: Translate ctx errors to gRPC status on session vRPC (#20299) (0f3b2a5)
• bigtable: Treat PingAndWarm NotFound as a successful prime (#20219) (a1557ad)
• bigtable: Use composed user agent as CSM client_name (#20383) (cb02335)
• bigtable: Use instance_name instead of name in GetClientConfig (#20465) (375f198)

Performance Improvements

• bigtable: Delete periodic Tick loop; sizing is event-driven (#20285) (2c096bd)
• bigtable: Drop pick_lost_race debug tag from CheckoutSession hot path (#20280) (bd0e400)

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