Oak 2.0.0 plus fixes

oak-segment-remote/src/main/java/org/apache/jackrabbit/oak/segment/remote/persistentcache/PersistentDiskCache.java

@@ -24,6 +24,7 @@
 import org.apache.jackrabbit.oak.commons.time.Stopwatch;
 import org.apache.jackrabbit.oak.segment.spi.persistence.persistentcache.AbstractPersistentCache;
 import org.apache.jackrabbit.oak.segment.spi.persistence.persistentcache.SegmentCacheStats;
+import org.apache.jackrabbit.oak.spi.toggle.FeatureToggle;
 import org.jetbrains.annotations.NotNull;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -58,6 +59,28 @@ public class PersistentDiskCache extends AbstractPersistentCache {
     public static final long DEFAULT_TEMP_FILES_CLEANUP_WAIT_TIME_MS = 60000;
     private static final String TEMP_FILE_SUFFIX = ".part";
 
+    /**
+     * Name of the feature toggle that controls the OAK-12212 fix, see
+     * {@link #FT_OAK_12212_SKIP_MISSING_FILE_CHECK}.
+     */
+    public static final String FT_OAK_12212 = "FT_OAK-12212";
+
+    /**
+     * Kill switch for the OAK-12212 fix in {@link #writeSegment}.
+     * <p>
+     * When {@code false} (default), {@code writeSegment} skips the on-disk
+     * write and the corresponding {@code cacheSize} increment if the segment
+     * is already present on disk. Segments are immutable, so a redundant
+     * write would only produce identical bytes — but every such call used to
+     * increment {@code cacheSize} while {@code Files.move} silently replaced
+     * the file on POSIX systems, causing the in-memory counter to drift far
+     * above the actual cache directory size and above {@code maxCacheSizeBytes}.
+     * <p>
+     * Set to {@code true} via the {@link FeatureToggle} registered with the
+     * Whiteboard to revert to the pre-fix behaviour.
+     */
+    public static final AtomicBoolean FT_OAK_12212_SKIP_MISSING_FILE_CHECK = new AtomicBoolean(false);
+
     private final File directory;
     private final long maxCacheSizeBytes;
     private final DiskCacheIOMonitor diskCacheIOMonitor;
@@ -148,17 +171,27 @@ public void writeSegment(long msb, long lsb, Buffer buffer) {
         Runnable task = () -> {
             if (writesPending.add(segmentId)) {
                 try {
-                    int fileSize;
-                    try (FileChannel channel = new FileOutputStream(tempSegmentFile).getChannel()) {
-                        fileSize = bufferCopy.write(channel);
-                    }
-                    try {
-                        Files.move(tempSegmentFile.toPath(), segmentFile.toPath(), StandardCopyOption.ATOMIC_MOVE);
-                    } catch (AtomicMoveNotSupportedException e) {
-                        Files.move(tempSegmentFile.toPath(), segmentFile.toPath());
+                    // OAK-12212: skip the on-disk write and the cacheSize
+                    // increment when the segment is already on disk. Segments
+                    // are immutable, so a redundant write would only rewrite
+                    // identical bytes; the pre-fix behaviour still incremented
+                    // cacheSize on every such call while Files.move silently
+                    // replaced the file on POSIX systems, leaking phantom
+                    // bytes into the in-memory counter on every redundant
+                    // write. Guarded by FT_OAK-12212 (disabled = active fix).
+                    if (FT_OAK_12212_SKIP_MISSING_FILE_CHECK.get() || !segmentFile.exists()) {
+                        int fileSize;
+                        try (FileChannel channel = new FileOutputStream(tempSegmentFile).getChannel()) {
+                            fileSize = bufferCopy.write(channel);
+                        }
+                        try {
+                            Files.move(tempSegmentFile.toPath(), segmentFile.toPath(), StandardCopyOption.ATOMIC_MOVE);
+                        } catch (AtomicMoveNotSupportedException e) {
+                            Files.move(tempSegmentFile.toPath(), segmentFile.toPath());
+                        }
+                        long cacheSizeAfter = cacheSize.addAndGet(fileSize);
+                        diskCacheIOMonitor.updateCacheSize(cacheSizeAfter, fileSize);
                     }
-                    long cacheSizeAfter = cacheSize.addAndGet(fileSize);
-                    diskCacheIOMonitor.updateCacheSize(cacheSizeAfter, fileSize);
                 } catch (Exception e) {
                     logger.error("Error writing segment {} to cache", segmentId, e);
                     try {

oak-segment-remote/src/main/java/org/apache/jackrabbit/oak/segment/remote/persistentcache/RemotePersistentCacheService.java

@@ -25,6 +25,7 @@
 import org.apache.jackrabbit.oak.osgi.OsgiWhiteboard;
 import org.apache.jackrabbit.oak.segment.spi.monitor.RoleStatisticsProvider;
 import org.apache.jackrabbit.oak.segment.spi.persistence.persistentcache.PersistentCache;
+import org.apache.jackrabbit.oak.spi.toggle.FeatureToggle;
 import org.apache.jackrabbit.oak.spi.whiteboard.Registration;
 import org.apache.jackrabbit.oak.spi.whiteboard.WhiteboardUtils;
 import org.apache.jackrabbit.oak.stats.StatisticsProvider;
@@ -38,6 +39,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.util.Collections;
 import java.util.Hashtable;
 
 @Component(
@@ -93,6 +95,12 @@ private PersistentCache createPersistentCache(Configuration configuration, Close
             PersistentDiskCache persistentDiskCache = new PersistentDiskCache(new File(configuration.diskCacheDirectory()), configuration.diskCacheMaxSizeMB(), diskCacheIOMonitor);
             closer.register(persistentDiskCache);
 
+            // OAK-12212: expose the kill switch for the cacheSize-accounting
+            // fix so it can be flipped at runtime via the Whiteboard.
+            registerCloseable(osgiWhiteboard.register(FeatureToggle.class,
+                    new FeatureToggle(PersistentDiskCache.FT_OAK_12212, PersistentDiskCache.FT_OAK_12212_SKIP_MISSING_FILE_CHECK),
+                    Collections.emptyMap()));
+
             CacheStatsMBean diskCacheStatsMBean = persistentDiskCache.getCacheStats();
             registerCloseable(registerMBean(CacheStatsMBean.class, diskCacheStatsMBean, CacheStats.TYPE, diskCacheStatsMBean.getName()));
 

oak-segment-remote/src/main/java/org/apache/jackrabbit/oak/segment/remote/persistentcache/package-info.java

@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-@Version("2.0.0")
+@Version("2.1.0")
 package org.apache.jackrabbit.oak.segment.remote.persistentcache;
 
 import org.osgi.annotation.versioning.Version;