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database/sql: context cancellation allows statements to execute after rollback [1.13 backport] #40205
Manually backported the subject CLs, because of lack of Gerrit "forge-author" permissions, but also because the prior cherry picks didn't apply cleanly, due to a tight relation chain. The backport comprises of: * CL 174122 * CL 216197 * CL 223963 * CL 216240 * CL 216241 Note: Due to the restrictions that we cannot retroactively introduce API changes to Go1.13.13 that weren't in Go1.13, the Conn.Validator interface (from CL 174122, CL 223963) isn't exposed, and drivers will just be inspected, for if they have an IsValid() bool method implemented. For a description of the content of each CL: * CL 174122: database/sql: process all Session Resets synchronously Adds a new interface, driver.ConnectionValidator, to allow drivers to signal they should not be used again, separatly from the session resetter interface. This is done now that the session reset is done after the connection is put into the connection pool. Previous behavior attempted to run Session Resets in a background worker. This implementation had two problems: untested performance gains for additional complexity, and failures when the pool size exceeded the connection reset channel buffer size. * CL 216197: database/sql: check conn expiry when returning to pool, not when handing it out With the original connection reuse strategy, it was possible that when a new connection was requested, the pool would wait for an an existing connection to return for re-use in a full connection pool, and then it would check if the returned connection was expired. If the returned connection expired while awaiting re-use, it would return an error to the location requestiong the new connection. The existing call sites requesting a new connection was often the last attempt at returning a connection for a query. This would then result in a failed query. This change ensures that we perform the expiry check right before a connection is inserted back in to the connection pool for while requesting a new connection. If requesting a new connection it will no longer fail due to the connection expiring. * CL 216240: database/sql: prevent Tx statement from committing after rollback It was possible for a Tx that was aborted for rollback asynchronously to execute a query after the rollback had completed on the database, which often would auto commit the query outside of the transaction. By W-locking the tx.closemu prior to issuing the rollback connection it ensures any Tx query either fails or finishes on the Tx, and never after the Tx has rolled back. * CL 216241: database/sql: on Tx rollback, retain connection if driver can reset session Previously the Tx would drop the connection after rolling back from a context cancel. Now if the driver can reset the session, keep the connection. * CL 223963 database/sql: add test for Conn.Validator interface This addresses comments made by Russ after https://golang.org/cl/174122 was merged. It addes a test for the connection validator and renames the interface to just "Validator". Updates #31480 Updates #32530 Updates #32942 Updates #34775 Fixes #40205 Change-Id: I6d7307180b0db0bf159130d91161764cf0f18b58 Reviewed-on: https://go-review.googlesource.com/c/go/+/242522 Run-TryBot: Emmanuel Odeke <firstname.lastname@example.org> TryBot-Result: Gobot Gobot <email@example.com> Reviewed-by: Daniel Theophanes <firstname.lastname@example.org>