Rename folding generation to rolling generation

core/src/main/java/org/elasticsearch/index/translog/Translog.java

@@ -127,7 +127,7 @@ public class Translog extends AbstractIndexShardComponent implements IndexShardC
     private final TranslogConfig config;
     private final LongSupplier globalCheckpointSupplier;
     private final String translogUUID;
-    private final AtomicBoolean foldingGeneration = new AtomicBoolean();
+    private final AtomicBoolean rollingGeneration = new AtomicBoolean();
 
     /**
      * Creates a new Translog instance. This method will create a new transaction log unless the given {@link TranslogGeneration} is
@@ -424,14 +424,14 @@ public Location add(final Operation operation) throws IOException {
                 ensureOpen();
                 location = current.add(bytes, operation.seqNo());
             }
-            if (shouldFoldGeneration() && foldingGeneration.compareAndSet(false, true)) {
-                // we have to check the condition again lest we could fold twice in a race
-                if (shouldFoldGeneration()) {
+            if (shouldRollGeneration() && rollingGeneration.compareAndSet(false, true)) {
+                // we have to check the condition again lest we could roll twice in a race
+                if (shouldRollGeneration()) {
                     try (ReleasableLock ignored = writeLock.acquire()) {
-                        this.foldGeneration();
+                        this.rollGeneration();
                     }
-                    final boolean wasFoldingGeneration = foldingGeneration.getAndSet(false);
-                    assert wasFoldingGeneration;
+                    final boolean wasRolling = rollingGeneration.getAndSet(false);
+                    assert wasRolling;
                 }
             }
             return location;
@@ -455,13 +455,13 @@ public Location add(final Operation operation) throws IOException {
     }
 
     /**
-     * Tests whether or not the current generation of the translog should be folded into a new
+     * Tests whether or not the current generation of the translog should be rolled into a new
      * generation. This test is based on the size of the current generation compared to the
      * configured generation threshold size.
      *
-     * @return {@code true} if the current generation should be folded into a new generation
+     * @return {@code true} if the current generation should be rolled into a new generation
      */
-    private boolean shouldFoldGeneration() {
+    private boolean shouldRollGeneration() {
         final long size = this.current.sizeInBytes();
         final long threshold = this.indexSettings.getGenerationThresholdSize().getBytes();
         return size > threshold;
@@ -1348,12 +1348,12 @@ public static void writeOperationNoSize(BufferedChecksumStreamOutput out, Transl
     }
 
     /**
-     * Fold the current translog generation into a new generation. This does not commit the
+     * Roll the current translog generation into a new generation. This does not commit the
      * translog. The translog write lock must be held by the current thread.
      *
      * @throws IOException if an I/O exception occurred during any file operations
      */
-    void foldGeneration() throws IOException {
+    void rollGeneration() throws IOException {
         assert writeLock.isHeldByCurrentThread();
         try {
             final TranslogReader reader = current.closeIntoReader();
@@ -1383,7 +1383,7 @@ public long prepareCommit() throws IOException {
                         currentCommittingGeneration);
             }
             currentCommittingGeneration = current.getGeneration();
-            foldGeneration();
+            rollGeneration();
         }
         return 0L;
     }

core/src/test/java/org/elasticsearch/index/translog/TranslogTests.java

@@ -2089,33 +2089,33 @@ public void testTranslogOpSerialization() throws Exception {
         assertEquals(delete, serializedDelete);
     }
 
-    public void testFoldGeneration() throws IOException {
+    public void testRollGeneration() throws IOException {
         final long generation = translog.currentFileGeneration();
-        final int folds = randomIntBetween(1, 16);
+        final int rolls = randomIntBetween(1, 16);
         int totalOperations = 0;
         int seqNo = 0;
-        for (int i = 0; i < folds; i++) {
+        for (int i = 0; i < rolls; i++) {
             final int operations = randomIntBetween(1, 128);
             for (int j = 0; j < operations; j++) {
                 translog.add(new Translog.NoOp(seqNo++, 0, "test"));
                 totalOperations++;
             }
             try (ReleasableLock ignored = translog.writeLock.acquire()) {
-                translog.foldGeneration();
+                translog.rollGeneration();
             }
             assertThat(translog.currentFileGeneration(), equalTo(generation + i + 1));
             assertThat(translog.totalOperations(), equalTo(totalOperations));
         }
-        for (int i = 0; i <= folds; i++) {
+        for (int i = 0; i <= rolls; i++) {
             assertFileIsPresent(translog, generation + i);
         }
         translog.commit();
-        assertThat(translog.currentFileGeneration(), equalTo(generation + folds + 1));
+        assertThat(translog.currentFileGeneration(), equalTo(generation + rolls + 1));
         assertThat(translog.totalOperations(), equalTo(0));
-        for (int i = 0; i <= folds; i++) {
+        for (int i = 0; i <= rolls; i++) {
             assertFileDeleted(translog, generation + i);
         }
-        assertFileIsPresent(translog, generation + folds + 1);
+        assertFileIsPresent(translog, generation + rolls + 1);
     }
 
     public void testGenerationThreshold() throws IOException {
@@ -2126,24 +2126,24 @@ public void testGenerationThreshold() throws IOException {
                 .put("index.translog.generation_threshold_size", generationThreshold + "b")
                 .build();
         long seqNo = 0;
-        long folds = 0;
+        long rolls = 0;
         final TranslogConfig config = getTranslogConfig(translogDir, settings);
         try (Translog translog =
                      new Translog(config, null, () -> SequenceNumbersService.UNASSIGNED_SEQ_NO)) {
             final long generation = translog.currentFileGeneration();
             for (int i = 0; i < randomIntBetween(32, 128); i++) {
-                assertThat(translog.currentFileGeneration(), equalTo(generation + folds));
+                assertThat(translog.currentFileGeneration(), equalTo(generation + rolls));
                 final Location location = translog.add(new Translog.NoOp(seqNo++, 0, "test"));
                 if (location.translogLocation + location.size > generationThreshold) {
-                    folds++;
-                    assertThat(translog.currentFileGeneration(), equalTo(generation + folds));
-                    for (int j = 0; j < folds; j++) {
+                    rolls++;
+                    assertThat(translog.currentFileGeneration(), equalTo(generation + rolls));
+                    for (int j = 0; j < rolls; j++) {
                         assertFileIsPresent(translog, generation + j);
                     }
                 }
             }
 
-            for (int j = 0; j < folds; j++) {
+            for (int j = 0; j < rolls; j++) {
                 assertFileIsPresent(translog, generation + j);
             }
         }