test(wal): cover RecoveryManagerTest and tempFile
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package kestrel.store.wal
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import kestrel.store.page.DiskManager
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import kestrel.store.page.Page
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import java.io.File
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import java.nio.file.Files
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import kotlin.test.Test
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import kotlin.test.assertContentEquals
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import kotlin.test.assertEquals
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import kotlin.test.assertFailsWith
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import kotlin.test.assertTrue
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class RecoveryManagerTest {
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private fun tempFile(prefix: String): File = Files.createTempFile(prefix, ".db").toFile().also { it.deleteOnExit() }
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private fun pageOf(fill: Int): ByteArray = ByteArray(Page.PAGE_SIZE) { fill.toByte() }
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@Test
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fun redoRestoresACommittedWriteThatNeverReachedTheDataFile() {
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val dataFile = tempFile("kestrel-recovery-data")
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val walFile = tempFile("kestrel-recovery-wal")
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val diskManager = DiskManager(dataFile)
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val pageId = diskManager.allocatePage()
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val before = pageOf(0)
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diskManager.writePage(Page(pageId).also { System.arraycopy(before, 0, it.data, 0, before.size) })
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val wal = WriteAheadLog(walFile)
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val txn = wal.beginTransaction()
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val after = pageOf(7)
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wal.logUpdate(txn, pageId, before, after)
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wal.commit(txn)
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// Simulate a crash: the buffer pool never flushed `after` to the data file,
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// but the WAL frame for the update and the commit are durable.
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val result = RecoveryManager(wal, diskManager).recover()
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assertEquals(1, result.redoneUpdates)
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assertTrue(result.rolledBackTxns.isEmpty())
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assertContentEquals(after, diskManager.readPage(pageId).data)
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}
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@Test
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fun undoRestoresAPageWrittenByATransactionThatNeverCommitted() {
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val dataFile = tempFile("kestrel-recovery-data")
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val walFile = tempFile("kestrel-recovery-wal")
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val diskManager = DiskManager(dataFile)
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val pageId = diskManager.allocatePage()
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val before = pageOf(1)
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diskManager.writePage(Page(pageId).also { System.arraycopy(before, 0, it.data, 0, before.size) })
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val wal = WriteAheadLog(walFile)
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val txn = wal.beginTransaction()
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val after = pageOf(9)
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wal.logUpdate(txn, pageId, before, after)
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// Simulate a crash before commit, after the dirty page happened to reach disk
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// under a steal buffer-pool policy.
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diskManager.writePage(Page(pageId).also { System.arraycopy(after, 0, it.data, 0, after.size) })
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val result = RecoveryManager(wal, diskManager).recover()
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assertEquals(listOf(txn), result.rolledBackTxns)
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assertContentEquals(before, diskManager.readPage(pageId).data)
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val abortSeen = wal.readFrom(0L).any { it.second is LogRecord.Abort && (it.second as LogRecord.Abort).txnId == txn }
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assertTrue(abortSeen, "expected recovery to append an Abort record resolving the transaction")
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}
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@Test
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fun checkpointSkipsReplayingUpdatesFromBeforeIt() {
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val dataFile = tempFile("kestrel-recovery-data")
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val walFile = tempFile("kestrel-recovery-wal")
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val diskManager = DiskManager(dataFile)
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val pageA = diskManager.allocatePage()
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val pageB = diskManager.allocatePage()
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diskManager.writePage(Page(pageA).also { System.arraycopy(pageOf(0), 0, it.data, 0, Page.PAGE_SIZE) })
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diskManager.writePage(Page(pageB).also { System.arraycopy(pageOf(0), 0, it.data, 0, Page.PAGE_SIZE) })
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val wal = WriteAheadLog(walFile)
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val firstTxn = wal.beginTransaction()
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wal.logUpdate(firstTxn, pageA, pageOf(0), pageOf(5))
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wal.commit(firstTxn)
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wal.checkpoint()
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val secondTxn = wal.beginTransaction()
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wal.logUpdate(secondTxn, pageB, pageOf(0), pageOf(6))
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wal.commit(secondTxn)
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val result = RecoveryManager(wal, diskManager).recover()
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assertEquals(1, result.redoneUpdates, "only the update after the checkpoint should be replayed")
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}
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@Test
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fun liveRollbackUndoesUpdatesWithoutACrash() {
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val dataFile = tempFile("kestrel-recovery-data")
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val walFile = tempFile("kestrel-recovery-wal")
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val diskManager = DiskManager(dataFile)
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val pageId = diskManager.allocatePage()
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val before = pageOf(2)
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diskManager.writePage(Page(pageId).also { System.arraycopy(before, 0, it.data, 0, before.size) })
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val wal = WriteAheadLog(walFile)
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val txn = wal.beginTransaction()
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val after = pageOf(8)
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wal.logUpdate(txn, pageId, before, after)
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diskManager.writePage(Page(pageId).also { System.arraycopy(after, 0, it.data, 0, after.size) })
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RecoveryManager(wal, diskManager).rollback(txn)
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assertContentEquals(before, diskManager.readPage(pageId).data)
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assertEquals(WriteAheadLog.NO_LSN, wal.lastLsnOf(txn))
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}
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@Test
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fun recoverDoesNotResurrectAWriteFromATransactionThatWasAbortedInAnEarlierSession() {
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val dataFile = tempFile("kestrel-recovery-data")
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val walFile = tempFile("kestrel-recovery-wal")
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val diskManager = DiskManager(dataFile)
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val pageId = diskManager.allocatePage()
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val before = pageOf(3)
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diskManager.writePage(Page(pageId).also { System.arraycopy(before, 0, it.data, 0, before.size) })
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val wal = WriteAheadLog(walFile)
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val txn = wal.beginTransaction()
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val after = pageOf(4)
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wal.logUpdate(txn, pageId, before, after)
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RecoveryManager(wal, diskManager).rollback(txn)
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// The transaction is now resolved (its Update is followed by an Abort record)
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// and the data file already holds `before`, exactly as a live abort left it.
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// A fresh WriteAheadLog reader over the same file, as a new process would open.
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val reopenedWal = WriteAheadLog(walFile)
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val result = RecoveryManager(reopenedWal, diskManager).recover()
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assertEquals(0, result.redoneUpdates, "an already-aborted transaction's update must not be replayed")
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assertTrue(result.rolledBackTxns.isEmpty())
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assertContentEquals(before, diskManager.readPage(pageId).data)
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}
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@Test
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fun rollingBackATransactionWithNoUpdatesJustMarksItAborted() {
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val walFile = tempFile("kestrel-recovery-wal")
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val dataFile = tempFile("kestrel-recovery-data")
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val wal = WriteAheadLog(walFile)
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val diskManager = DiskManager(dataFile)
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val txn = wal.beginTransaction()
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RecoveryManager(wal, diskManager).rollback(txn)
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assertEquals(WriteAheadLog.NO_LSN, wal.lastLsnOf(txn))
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val abortSeen = wal.readFrom(0L).any { it.second is LogRecord.Abort && (it.second as LogRecord.Abort).txnId == txn }
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assertTrue(abortSeen)
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}
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