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feat(bigtable): add ClientConfig.DisableSession to opt out of session backend - #20297
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sushanb merged 1 commit intoAug 3, 2026
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Adds a DisableSession bool field to ClientConfig. When true,
NewClientWithConfig skips constructing the session data-plane client
(sessionImpl) and the per-resource TableAPI cache (sessionTables)
entirely. Every downstream reader (open.go's getOrCreateSession*,
Client.Close, sessionTableCache.close) already nil-guards on that
state — the preDialed path has been producing nil sessionImpl
since day one, so the DisableSession path piggybacks on the same
escape route.
Motivation. Session infrastructure is currently constructed
unconditionally by NewClientWithConfig — a second gRPC channel pool
plus per-channel background goroutines (transport reader/writer,
balancer, resolver, callback serializer, xDS outlier-detection,
RLS). Measured cost on a 100 R + 100 W QPS workload with
CBT_FORCE_SESSION unset (session traffic quiet, infra idle):
+17 MB RSS
+363 goroutines
vs the same workload against the released classic-only build.
Callers with specific reasons to opt out — running against a
backend that doesn't support session mode, benchmarking classic
baselines, resource-constrained environments — pay that cost for
infrastructure they never touch. DisableSession lets them skip it.
Effect on Table. Open() still builds a TableShim (Diverter is a
classic-side concern), but the shim's session TableAPI is nil, so
TableShim.useSession() reports false regardless of Diverter's
SessionLoad. Every Apply / ReadRow routes to the classic path
unconditionally. Same behavior as callers who pre-dial a custom
gRPC conn today.
Default (false). Behavior is unchanged: session client is
constructed by NewClientWithConfig as it has been.
Tests. Three unit tests in a new client_disable_session_test.go:
- SkipsSessionInit — bufconn + WithContextDialer keeps preDialed
false so ONLY the DisableSession gate can be responsible for
sessionImpl being nil. Asserts sessionImpl == nil and
sessionTables == nil.
- ClientCloseWorks — DisableSession client's Close is clean,
idempotent on the nil-sessionImpl path.
- OpenTableRoutesClassicOnly — even with Diverter.SessionLoad
force-set to 1.0, TableShim.useSession() reports false because
shim.session is nil.
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This pull request introduces a DisableSession option to ClientConfig in the Bigtable client, allowing callers to opt out of constructing the session data-plane client and run classic-only to save resources. Comprehensive tests have been added to verify that session initialization is skipped, client closure is safe, and table operations route classic-only. The review feedback suggests removing an unnecessary defensive nil-guard on c.diverter in the tests, as it is guaranteed to be non-nil by construction.
mutianf
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Aug 3, 2026
sushanb
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Aug 3, 2026
🤖 I have created a release *beep* *boop* --- ## [1.52.0](bigtable/v1.51.0...bigtable/v1.52.0) (2026-08-03) ### Features * **bigtable:** Add AFE picker (Simple / LeastInFlight / LeastLatency) ([#20204](#20204)) ([bcbf714](bcbf714)) * **bigtable:** Add ClientConfig.DisableSession to opt out of session backend ([#20297](#20297)) ([7ee5e44](7ee5e44)) * **bigtable:** Add getClientConfigDirectAccessChecker for session pools ([#20209](#20209)) ([3b8d30a](3b8d30a)) * **bigtable:** Add NoOpChannelPrimer for session channel pools ([#20208](#20208)) ([d055a8a](d055a8a)) * **bigtable:** Add per-AFE sessionList for the two-tier session pool ([#20224](#20224)) ([dbf0c3f](dbf0c3f)) * **bigtable:** Add protoRowToRow conversion helper for TableShim ([#20257](#20257)) ([1297143](1297143)) * **bigtable:** Add Session debug surface (observability fields + methods) ([#20211](#20211)) ([d8d3e16](d8d3e16)) * **bigtable:** Add Session lifecycle (Start, Close, ForceClose, readLoop, heartBeatLoop) ([#20215](#20215)) ([b9e53c6](b9e53c6)) * **bigtable:** Add Session struct + state machine ([#20117](#20117)) ([09acbb3](09acbb3)) * **bigtable:** Add session.Config.EnableDebug to gate sessionz debug state ([#20247](#20247)) ([ce74c31](ce74c31)) * **bigtable:** Add SessionClient + SessionTable + lazyPool ([#20228](#20228)) ([ab2c96c](ab2c96c)) * **bigtable:** Add SessionPoolImpl (two-tier pool + scaling + debug) ([#20225](#20225)) ([683eda8](683eda8)) * **bigtable:** Rename session pool display to <resource-id>-<PERM> ([#20248](#20248)) ([35e146e](35e146e)) * **bigtable:** Route Client.Open()-returned *Table through the Diverter ([#20273](#20273)) ([2b81c7d](2b81c7d)) * **bigtable:** State-based classification for abnormal session close ([#20243](#20243)) ([f2905b7](f2905b7)) * **bigtable:** TableShim fallback to classic on session UNIMPLEMENTED ([#20269](#20269)) ([36540af](36540af)) * **bigtable:** TTL-on-idle cache for per-resource session.TableAPI ([#20263](#20263)) ([00b2a49](00b2a49)) * **bigtable:** Wire Diverter on Client and route Open* via TableShim ([#20256](#20256)) ([b32fbd7](b32fbd7)) ### Bug Fixes * **bigtable:** AFE picker latency signal — subtract poolWait and compute TransportLatency = wire − backend at source ([#20281](#20281)) ([bb8c4d5](bb8c4d5)) * **bigtable:** Guard NewStream OnFinish against grpc-go double-fire ([#20295](#20295)) ([b51da29](b51da29)) * **bigtable:** Real per-resource pool teardown on sessionTable.Close + cache close-race gate ([#20264](#20264)) ([599aea9](599aea9)) * **bigtable:** Session.durations / session.uptime — set explicit histogram bucket boundaries ([#20276](#20276)) ([97eee22](97eee22)) * **bigtable:** SessionTableHandle self-heals across cache eviction ([#20296](#20296)) ([0dd98cd](0dd98cd)) * **bigtable:** Translate ctx errors to gRPC status on session vRPC ([#20299](#20299)) ([0f3b2a5](0f3b2a5)) * **bigtable:** Treat PingAndWarm NotFound as a successful prime ([#20219](#20219)) ([a1557ad](a1557ad)) ### Performance Improvements * **bigtable:** Delete periodic Tick loop; sizing is event-driven ([#20285](#20285)) ([2c096bd](2c096bd)) * **bigtable:** Drop pick_lost_race debug tag from CheckoutSession hot path ([#20280](#20280)) ([bd0e400](bd0e400)) --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please). Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
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