[cbalan]

Backport of upstream k3s-io#795 (commit k3s-io/kine@f805442, "Fix connection leak in Migrate") to the v0.17.2 release line, as a fix(fork) commit per the fork policy. The upstream patch applies cleanly here.

Replay note: upstream v0.17.3 and later already contain this fix and then remove Migrate altogether ("Drop migration support", same upstream PR). Drop this commit when replaying the fork commits onto a release line cut from v0.17.3 or later; it conflicts in pkg/drivers/generic/generic.go there.

Why

On this branch TestCompact fails on cgo SQLite: the post-compaction PRAGMA wal_checkpoint(FULL) waits out the full 30 s _busy_timeout, and the apiserver test cancels the Compact call. This is the Test sqlite failure that #35 merged with.

Root cause: Generic.Migrate opened both COUNT(*) rows up front and returned after the first Scan failed (no key_value table), so the second row was never read and kept its connection checked out. With _stmt_cache_size=20 in DefaultParams, go-sqlite3 steps the cached statement eagerly, so that leaked connection also holds a read transaction on the startup snapshot. FULL waits for every reader to reach the latest snapshot, so it blocks until the busy timeout.

Pinning the golang:1.26-alpine3.23 digest would not fix this: the stall reproduces locally on Go 1.26.5, 1.26.8 and 1.26.10.

Changes

• pkg/drivers/generic/generic.go: query kine only after the key_value row has been scanned and warrants it.
• pkg/drivers/sqlite/sqlite_test.go: adds upstream's TestMigrateReleasesItsConnections (1-connection pool, DB must stay usable after Migrate).

Testing

• Local repro (default DSN, busy timeout lowered to 3 s, one write, then wal_checkpoint(FULL)): before the fix, busy=1 after 3.1 s with 1 connection still in use; after, busy=0 in about 0.25 ms. Same result for cgo (mattn, SQLite 3.53.4) and nocgo (modernc).
• TestMigrateReleasesItsConnections passes with CGO_ENABLED=1 and CGO_ENABLED=0.
• CGO_ENABLED=1 go test ./pkg/drivers/... ./pkg/logstructured/... passes.
• The full apiserver TestCompact suite was not run locally; the SQLite CI jobs on this PR cover it.

Refs: ENGCP-1950

🤖 Generated with Claude Code

[Piotr1215]

LGTM. Verified the upstream patch and the regression test with cgo and nocgo.