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docs(bigtable): clarify session close, cancelRpc, and heartbeat invariants - #15000
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igorbernstein2 wants to merge 1 commit into
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This pull request enhances the documentation and inline comments in Session.java and SessionImpl.java to clarify the Session V3 protocol state transitions, graceful close behavior, RPC cancellation mechanics, and timeout handling. Specifically, it explains why a session waits in the CLOSING state during active vRPCs and details the server-side invariants bounding this state. There are no review comments, and I have no additional feedback to provide.
mutianf
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Nov 13, 2026
| * sent. Bounded by server heartbeats ({@code checkHeartbeat}) and the server-enforced | ||
| * {@code VirtualRpcRequest.deadline}. | ||
| * <li>{@link #WAIT_SERVER_CLOSE}: No vRPC is in flight on the wire (so server heartbeats stop) | ||
| * and {@code CloseSessionRequest} + {@code halfClose()} have been sent; waiting for the |
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hmm, i just realized, we send another CloseSessionRequest when watchdog kills the session, is it gonna be redundant? maybe log a debug tag is enough?
mutianf
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Nov 13, 2026
| public void cancelRpc(long rpcId, @Nullable String message, @Nullable Throwable cause) { | ||
| sessionSyncContext.execute( | ||
| () -> { | ||
| // The Session V3 protocol does not yet have a wire cancel-vRPC message, so the server |
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Clarifies the Session lifecycle,
cancelRpc, and server heartbeat/deadline contracts inSessionandSessionImpl:Session.close()(which previously described immediate abort likeforceClose()rather than graceful drain viaCLOSING->WAIT_SERVER_CLOSE) and document how eachSessionStateis bounded.SessionImpl.cancelRpc()andSessionImpl.close()whycurrentRpcremains set after local cancellation until the server replies (the protocol does not yet have a wire cancel-vRPC message, so keepingcurrentRpcset prevents returning aREADYsession to the pool while the vRPC is still active on the server and prevents sendingCloseSessionRequestwhile a vRPC is still in flight on the server).SessionImpl.checkCloseTimeout()whycloseTimeoutonly needs to boundWAIT_SERVER_CLOSE(CLOSINGonly occurs while a vRPC is active on the wire, which is bounded by server heartbeats viacheckHeartbeat()and the server-enforcedVirtualRpcRequest.deadline).