satishd commented on code in PR #13850:
URL: https://github.com/apache/kafka/pull/13850#discussion_r1231867641
##########
core/src/main/scala/kafka/log/remote/RemoteIndexCache.scala:
##########
@@ -37,88 +40,125 @@ object RemoteIndexCache {
val TmpFileSuffix = ".tmp"
}
-class Entry(val offsetIndex: OffsetIndex, val timeIndex: TimeIndex, val
txnIndex: TransactionIndex) {
+class Entry(val offsetIndex: OffsetIndex, val timeIndex: TimeIndex, val
txnIndex: TransactionIndex) extends AutoCloseable {
private var markedForCleanup: Boolean = false
- private val lock: ReentrantReadWriteLock = new ReentrantReadWriteLock()
+ private val entryLock: ReentrantReadWriteLock = new ReentrantReadWriteLock()
def lookupOffset(targetOffset: Long): OffsetPosition = {
- CoreUtils.inLock(lock.readLock()) {
+ inReadLock(entryLock) {
if (markedForCleanup) throw new IllegalStateException("This entry is
marked for cleanup")
else offsetIndex.lookup(targetOffset)
}
}
def lookupTimestamp(timestamp: Long, startingOffset: Long): OffsetPosition =
{
- CoreUtils.inLock(lock.readLock()) {
+ inReadLock(entryLock) {
if (markedForCleanup) throw new IllegalStateException("This entry is
marked for cleanup")
-
val timestampOffset = timeIndex.lookup(timestamp)
offsetIndex.lookup(math.max(startingOffset, timestampOffset.offset))
}
}
def markForCleanup(): Unit = {
- CoreUtils.inLock(lock.writeLock()) {
+ inWriteLock(entryLock) {
if (!markedForCleanup) {
markedForCleanup = true
Array(offsetIndex, timeIndex).foreach(index =>
index.renameTo(new File(Utils.replaceSuffix(index.file.getPath, "",
LogFileUtils.DELETED_FILE_SUFFIX))))
+ // txn index needs to be renamed separately since it's not of type
AbstractIndex
txnIndex.renameTo(new File(Utils.replaceSuffix(txnIndex.file.getPath,
"",
LogFileUtils.DELETED_FILE_SUFFIX)))
}
}
}
+ /**
+ * Deletes the index files from the disk. Invoking #close is not required
prior to this function.
+ */
def cleanup(): Unit = {
markForCleanup()
CoreUtils.tryAll(Seq(() => offsetIndex.deleteIfExists(), () =>
timeIndex.deleteIfExists(), () => txnIndex.deleteIfExists()))
}
+ /**
+ * Calls the underlying close method for each index which may lead to
releasing resources such as mmap.
+ * This function does not delete the index files.
+ */
def close(): Unit = {
- Array(offsetIndex, timeIndex).foreach(index => try {
- index.close()
- } catch {
- case _: Exception => // ignore error.
- })
+ Utils.closeQuietly(offsetIndex, "Closing the offset index.")
+ Utils.closeQuietly(timeIndex, "Closing the time index.")
Utils.closeQuietly(txnIndex, "Closing the transaction index.")
}
}
/**
* This is a LRU cache of remote index files stored in
`$logdir/remote-log-index-cache`. This is helpful to avoid
- * re-fetching the index files like offset, time indexes from the remote
storage for every fetch call.
+ * re-fetching the index files like offset, time indexes from the remote
storage for every fetch call. The cache is
+ * re-initialized from the index files on disk on startup, if the index files
are available.
+ *
+ * The cache contains a garbage collection thread which will delete the files
for entries that have been removed from
+ * the cache.
+ *
+ * Note that closing this cache does not delete the index files on disk.
+ * Note that this cache is not strictly based on a LRU policy. It is based on
the default implementation of Caffeine i.e.
+ * <a href="https://github.com/ben-manes/caffeine/wiki/Efficiency";>Window
TinyLfu</a>. TinyLfu relies on a frequency
+ * sketch to probabilistically estimate the historic usage of an entry.
*
* @param maxSize maximum number of segment index entries to be
cached.
* @param remoteStorageManager RemoteStorageManager instance, to be used in
fetching indexes.
* @param logDir log directory
*/
+@threadsafe
class RemoteIndexCache(maxSize: Int = 1024, remoteStorageManager:
RemoteStorageManager, logDir: String)
- extends Logging with Closeable {
-
- val cacheDir = new File(logDir, DirName)
- @volatile var closed = false
-
- val expiredIndexes = new LinkedBlockingQueue[Entry]()
- val lock = new Object()
-
- val entries: util.Map[Uuid, Entry] = new java.util.LinkedHashMap[Uuid,
Entry](maxSize / 2,
- 0.75f, true) {
- override def removeEldestEntry(eldest: util.Map.Entry[Uuid, Entry]):
Boolean = {
- if (this.size() > maxSize) {
- val entry = eldest.getValue
- // Mark the entries for cleanup, background thread will clean them
later.
- entry.markForCleanup()
- expiredIndexes.add(entry)
- true
- } else {
- false
- }
- }
- }
+ extends Logging with AutoCloseable {
+ /**
+ * Directory where the index files will be stored on disk.
+ */
+ private val cacheDir = new File(logDir, DirName)
+ /**
+ * Represents if the cache is closed or not. Closing the cache is an
irreversible operation.
+ */
+ private val closed: AtomicBoolean = new AtomicBoolean(false)
+ /**
+ * Unbounded queue containing the removed entries from the cache which are
waiting to be garbage collected.
+ */
+ private val expiredIndexes = new LinkedBlockingQueue[Entry]()
+ /**
+ * Actual cache implementation that this file wraps around.
+ *
+ * The requirements for this internal cache is as follows:
+ * 1. Multiple threads should be able to read concurrently.
+ * 2. Fetch for missing keys should not block read for available keys.
+ * 3. Only one thread should fetch for a specific key.
+ * 4. Should support LRU policy.
+ *
+ * We use [[Caffeine]] cache instead of implementing a thread safe LRU cache
on our own.
+ *
+ * Visible for testing.
+ */
+ private[remote] var internalCache: Cache[Uuid, Entry] = Caffeine.newBuilder()
+ .maximumSize(maxSize)
+ // removeListener is invoked when either the entry is invalidated (means
manual removal by the caller) or
+ // evicted (means removal due to the policy)
+ .removalListener((_: Uuid, entry: Entry, _: RemovalCause) => {
+ // Mark the entries for cleanup and add them to the queue to be garbage
collected later by the background thread.
+ entry.markForCleanup()
+ expiredIndexes.add(entry)
+ })
+ .build[Uuid, Entry]()
+
private def init(): Unit = {
- if (cacheDir.mkdir())
+ try {
+ Files.createDirectory(cacheDir.toPath)
info(s"Created $cacheDir successfully")
+ } catch {
+ case _: FileAlreadyExistsException =>
+ info(s"RemoteIndexCache directory $cacheDir already exists. Re-using
the same directory.")
+ case e: Exception =>
+ error(s"Unable to create directory $cacheDir for RemoteIndexCache.", e)
+ throw new IllegalArgumentException(e)
Review Comment:
Why is it wrapped as `IllegalArgumentException`?
##########
core/src/test/scala/unit/kafka/log/remote/RemoteIndexCacheTest.scala:
##########
@@ -170,44 +190,173 @@ class RemoteIndexCacheTest {
assertThrows(classOf[IllegalStateException], () =>
cache.getIndexEntry(metadataList.head))
}
+ @Test
+ def testCloseIsIdempotent(): Unit = {
+ val spyCleanerThread = spy(cache.cleanerThread)
+ cache.cleanerThread = spyCleanerThread
+ cache.close()
+ cache.close()
+ // verify that cleanup is only called once
+ verify(spyCleanerThread).initiateShutdown()
+ }
+
+ @Test
+ def testClose(): Unit = {
+ val spyInternalCache = spy(cache.internalCache)
+ val spyCleanerThread = spy(cache.cleanerThread)
+
+ // replace with new spy cache
+ cache.internalCache = spyInternalCache
+ cache.cleanerThread = spyCleanerThread
+
+ // use the cache
+ val tpId = new TopicIdPartition(Uuid.randomUuid(), new
TopicPartition("foo", 0))
+ val metadataList = generateRemoteLogSegmentMetadata(size = 1, tpId)
+ val entry = cache.getIndexEntry(metadataList.head)
+
+ val spyTxnIndex = spy(entry.txnIndex)
+ val spyOffsetIndex = spy(entry.offsetIndex)
+ val spyTimeIndex = spy(entry.timeIndex)
+ // remove this entry and replace with spied entry
+ cache.internalCache.invalidateAll()
+ cache.internalCache.put(metadataList.head.remoteLogSegmentId().id(), new
Entry(spyOffsetIndex, spyTimeIndex, spyTxnIndex))
+
+ // close the cache
+ cache.close()
+
+ // cleaner thread should be closed properly
+ verify(spyCleanerThread).initiateShutdown()
+ verify(spyCleanerThread).awaitShutdown()
+
+ // close for all index entries must be invoked
+ verify(spyTxnIndex).close()
+ verify(spyOffsetIndex).close()
+ verify(spyTimeIndex).close()
+
+ // index files must not be deleted
+ verify(spyTxnIndex, times(0)).deleteIfExists()
+ verify(spyOffsetIndex, times(0)).deleteIfExists()
+ verify(spyTimeIndex, times(0)).deleteIfExists()
+ }
+
+ @Test
+ def testConcurrentReadWriteAccessForCache(): Unit = {
+ val tpId = new TopicIdPartition(Uuid.randomUuid(), new
TopicPartition("foo", 0))
+ val metadataList = generateRemoteLogSegmentMetadata(size = 3, tpId)
+
+ assertCacheSize(0)
+ // getIndex for first time will call rsm#fetchIndex
+ cache.getIndexEntry(metadataList.head)
+ assertCacheSize(1)
+ verifyFetchIndexInvocation(count = 1, Seq(IndexType.OFFSET,
IndexType.TIMESTAMP))
+ reset(rsm)
+
+ // Simulate a concurrency situation where one thread is reading the entry
already present in the cache (cache hit)
+ // and the other thread is reading an entry which is not available in the
cache (cache miss). The expected behaviour
+ // is for the former thread to succeed while latter is fetching from rsm.
+ // In this this test we simulate the situation using latches. We perform
the following operations:
+ // 1. Start the CacheMiss thread and wait until it starts executing the
rsm.fetchIndex
+ // 2. Block the CacheMiss thread inside the call to rsm.fetchIndex.
+ // 3. Start the CacheHit thread. Assert that it performs a successful read.
+ // 4. On completion of successful read by CacheHit thread, signal the
CacheMiss thread to release it's block.
+ // 5. Validate that the test passes. If the CacheMiss thread was blocking
the CacheHit thread, the test will fail.
+ //
+ val latchForCacheHit = new CountDownLatch(1)
+ val latchForCacheMiss = new CountDownLatch(1)
+
+ val readerCacheHit = (() => {
+ // Wait for signal to start executing the read
+ logger.debug(s"Waiting for signal to begin read from
${Thread.currentThread()}")
+ latchForCacheHit.await()
+ val entry = cache.getIndexEntry(metadataList.head)
+ assertNotNull(entry)
+ // Signal the CacheMiss to unblock itself
+ logger.debug(s"Signaling CacheMiss to unblock from
${Thread.currentThread()}")
+ latchForCacheMiss.countDown()
+ }): Runnable
+
+ when(rsm.fetchIndex(any(classOf[RemoteLogSegmentMetadata]),
any(classOf[IndexType])))
+ .thenAnswer(_ => {
+ logger.debug(s"Signaling CacheHit to begin read from
${Thread.currentThread()}")
+ latchForCacheHit.countDown()
+ logger.debug("Waiting for signal to complete rsm fetch from" +
Thread.currentThread())
+ latchForCacheMiss.await()
+ })
+
+ val readerCacheMiss = (() => {
+ val entry = cache.getIndexEntry(metadataList.last)
+ assertNotNull(entry)
+ }): Runnable
+
+ val executor = Executors.newFixedThreadPool(2)
+ try {
+ executor.submit(readerCacheMiss: Runnable)
+ executor.submit(readerCacheHit: Runnable)
+ assertTrue(latchForCacheMiss.await(30, TimeUnit.SECONDS))
+ } finally {
+ executor.shutdownNow()
+ }
+ }
+
@Test
def testReloadCacheAfterClose(): Unit = {
- val cache = new RemoteIndexCache(maxSize = 2, rsm, logDir =
logDir.toString)
+ // close exiting cache created in test setup before creating a new one
Review Comment:
nit typo: `exiting` -> `existing`
##########
core/src/main/scala/kafka/log/remote/RemoteIndexCache.scala:
##########
@@ -167,14 +210,14 @@ class RemoteIndexCache(maxSize: Int = 1024,
remoteStorageManager: RemoteStorageM
init()
// Start cleaner thread that will clean the expired entries
- val cleanerThread: ShutdownableThread = new
ShutdownableThread("remote-log-index-cleaner") {
+ private[remote] var cleanerThread: ShutdownableThread = new
ShutdownableThread("remote-log-index-cleaner") {
Review Comment:
Can you leave it as `val` instead of setting it as null in close?
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