Remove checkpoint tracker bit sets setting

We added an index-level setting for controlling the size of the bit sets
used to back the local checkpoint tracker. This setting is really only
needed to control the memory footprint of the bit sets but we do not
think this setting is going to be needed. This commit removes this
setting before it is released to the wild after which we would have to
worry about BWC implications.

Relates elastic#27191

Author: jasontedor

core/src/main/java/org/elasticsearch/common/settings/IndexScopedSettings.java

@@ -120,7 +120,6 @@ public final class IndexScopedSettings extends AbstractScopedSettings {
         IndexSettings.QUERY_STRING_LENIENT_SETTING,
         IndexSettings.ALLOW_UNMAPPED,
         IndexSettings.INDEX_CHECK_ON_STARTUP,
-        LocalCheckpointTracker.SETTINGS_BIT_ARRAYS_SIZE,
         IndexSettings.MAX_REFRESH_LISTENERS_PER_SHARD,
         IndexSettings.MAX_SLICES_PER_SCROLL,
         ShardsLimitAllocationDecider.INDEX_TOTAL_SHARDS_PER_NODE_SETTING,

core/src/main/java/org/elasticsearch/index/seqno/LocalCheckpointTracker.java

@@ -34,22 +34,16 @@ public class LocalCheckpointTracker {
 
     /**
      * We keep a bit for each sequence number that is still pending. To optimize allocation, we do so in multiple arrays allocating them on
-     * demand and cleaning up while completed. This setting controls the size of the arrays.
+     * demand and cleaning up while completed. This constant controls the size of the arrays.
      */
-    public static Setting<Integer> SETTINGS_BIT_ARRAYS_SIZE =
-        Setting.intSetting("index.seq_no.checkpoint.bit_arrays_size", 1024, 4, Setting.Property.IndexScope);
+    static final int BIT_ARRAYS_SIZE = 1024;
 
     /**
      * An ordered list of bit arrays representing pending sequence numbers. The list is "anchored" in {@link #firstProcessedSeqNo} which
      * marks the sequence number the fist bit in the first array corresponds to.
      */
     final LinkedList<FixedBitSet> processedSeqNo = new LinkedList<>();
 
-    /**
-     * The size of each bit set representing processed sequence numbers.
-     */
-    private final int bitArraysSize;
-
     /**
      * The sequence number that the first bit in the first array corresponds to.
      */
@@ -70,11 +64,10 @@ public class LocalCheckpointTracker {
      * {@link SequenceNumbers#NO_OPS_PERFORMED} and {@code localCheckpoint} should be set to the last known local checkpoint,
      * or {@link SequenceNumbers#NO_OPS_PERFORMED}.
      *
-     * @param indexSettings   the index settings
      * @param maxSeqNo        the last sequence number assigned, or {@link SequenceNumbers#NO_OPS_PERFORMED}
      * @param localCheckpoint the last known local checkpoint, or {@link SequenceNumbers#NO_OPS_PERFORMED}
      */
-    public LocalCheckpointTracker(final IndexSettings indexSettings, final long maxSeqNo, final long localCheckpoint) {
+    public LocalCheckpointTracker(final long maxSeqNo, final long localCheckpoint) {
         if (localCheckpoint < 0 && localCheckpoint != SequenceNumbers.NO_OPS_PERFORMED) {
             throw new IllegalArgumentException(
                 "local checkpoint must be non-negative or [" + SequenceNumbers.NO_OPS_PERFORMED + "] "
@@ -84,7 +77,6 @@ public LocalCheckpointTracker(final IndexSettings indexSettings, final long maxS
             throw new IllegalArgumentException(
                 "max seq. no. must be non-negative or [" + SequenceNumbers.NO_OPS_PERFORMED + "] but was [" + maxSeqNo + "]");
         }
-        bitArraysSize = SETTINGS_BIT_ARRAYS_SIZE.get(indexSettings.getSettings());
         firstProcessedSeqNo = localCheckpoint == SequenceNumbers.NO_OPS_PERFORMED ? 0 : localCheckpoint + 1;
         nextSeqNo = maxSeqNo == SequenceNumbers.NO_OPS_PERFORMED ? 0 : maxSeqNo + 1;
         checkpoint = localCheckpoint;
@@ -183,7 +175,7 @@ synchronized void waitForOpsToComplete(final long seqNo) throws InterruptedExcep
     @SuppressForbidden(reason = "Object#notifyAll")
     private void updateCheckpoint() {
         assert Thread.holdsLock(this);
-        assert checkpoint < firstProcessedSeqNo + bitArraysSize - 1 :
+        assert checkpoint < firstProcessedSeqNo + BIT_ARRAYS_SIZE - 1 :
             "checkpoint should be below the end of the first bit set (o.w. current bit set is completed and shouldn't be there)";
         assert getBitSetForSeqNo(checkpoint + 1) == processedSeqNo.getFirst() :
             "checkpoint + 1 doesn't point to the first bit set (o.w. current bit set is completed and shouldn't be there)";
@@ -196,10 +188,10 @@ assert getBitSetForSeqNo(checkpoint + 1).get(seqNoToBitSetOffset(checkpoint + 1)
                 checkpoint++;
                 // the checkpoint always falls in the first bit set or just before. If it falls
                 // on the last bit of the current bit set, we can clean it.
-                if (checkpoint == firstProcessedSeqNo + bitArraysSize - 1) {
+                if (checkpoint == firstProcessedSeqNo + BIT_ARRAYS_SIZE - 1) {
                     processedSeqNo.removeFirst();
-                    firstProcessedSeqNo += bitArraysSize;
-                    assert checkpoint - firstProcessedSeqNo < bitArraysSize;
+                    firstProcessedSeqNo += BIT_ARRAYS_SIZE;
+                    assert checkpoint - firstProcessedSeqNo < BIT_ARRAYS_SIZE;
                     current = processedSeqNo.peekFirst();
                 }
             } while (current != null && current.get(seqNoToBitSetOffset(checkpoint + 1)));
@@ -218,13 +210,13 @@ assert getBitSetForSeqNo(checkpoint + 1).get(seqNoToBitSetOffset(checkpoint + 1)
     private FixedBitSet getBitSetForSeqNo(final long seqNo) {
         assert Thread.holdsLock(this);
         assert seqNo >= firstProcessedSeqNo : "seqNo: " + seqNo + " firstProcessedSeqNo: " + firstProcessedSeqNo;
-        final long bitSetOffset = (seqNo - firstProcessedSeqNo) / bitArraysSize;
+        final long bitSetOffset = (seqNo - firstProcessedSeqNo) / BIT_ARRAYS_SIZE;
         if (bitSetOffset > Integer.MAX_VALUE) {
             throw new IndexOutOfBoundsException(
                 "sequence number too high; got [" + seqNo + "], firstProcessedSeqNo [" + firstProcessedSeqNo + "]");
         }
         while (bitSetOffset >= processedSeqNo.size()) {
-            processedSeqNo.add(new FixedBitSet(bitArraysSize));
+            processedSeqNo.add(new FixedBitSet(BIT_ARRAYS_SIZE));
         }
         return processedSeqNo.get((int) bitSetOffset);
     }
@@ -239,7 +231,7 @@ private FixedBitSet getBitSetForSeqNo(final long seqNo) {
     private int seqNoToBitSetOffset(final long seqNo) {
         assert Thread.holdsLock(this);
         assert seqNo >= firstProcessedSeqNo;
-        return ((int) (seqNo - firstProcessedSeqNo)) % bitArraysSize;
+        return ((int) (seqNo - firstProcessedSeqNo)) % BIT_ARRAYS_SIZE;
     }
 
 }

core/src/main/java/org/elasticsearch/index/seqno/SequenceNumbersService.java

@@ -56,7 +56,7 @@ public SequenceNumbersService(
         final long localCheckpoint,
         final long globalCheckpoint) {
         super(shardId, indexSettings);
-        localCheckpointTracker = new LocalCheckpointTracker(indexSettings, maxSeqNo, localCheckpoint);
+        localCheckpointTracker = new LocalCheckpointTracker(maxSeqNo, localCheckpoint);
         globalCheckpointTracker = new GlobalCheckpointTracker(shardId, allocationId, indexSettings, globalCheckpoint);
     }
 

core/src/main/java/org/elasticsearch/indices/recovery/RecoverySourceHandler.java

@@ -243,7 +243,7 @@ boolean isTranslogReadyForSequenceNumberBasedRecovery() throws IOException {
 
             logger.trace("all operations up to [{}] completed, checking translog content", endingSeqNo);
 
-            final LocalCheckpointTracker tracker = new LocalCheckpointTracker(shard.indexSettings(), startingSeqNo, startingSeqNo - 1);
+            final LocalCheckpointTracker tracker = new LocalCheckpointTracker(startingSeqNo, startingSeqNo - 1);
             try (Translog.Snapshot snapshot = shard.getTranslog().newSnapshotFromMinSeqNo(startingSeqNo)) {
                 Translog.Operation operation;
                 while ((operation = snapshot.next()) != null) {

core/src/test/java/org/elasticsearch/index/seqno/LocalCheckpointTrackerTests.java

@@ -21,10 +21,8 @@
 
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.common.Randomness;
-import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.concurrent.AbstractRunnable;
 import org.elasticsearch.test.ESTestCase;
-import org.elasticsearch.test.IndexSettingsModule;
 import org.junit.Before;
 
 import java.util.ArrayList;
@@ -38,6 +36,7 @@
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+import static org.elasticsearch.index.seqno.LocalCheckpointTracker.BIT_ARRAYS_SIZE;
 import static org.hamcrest.Matchers.empty;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.isOneOf;
@@ -46,19 +45,8 @@ public class LocalCheckpointTrackerTests extends ESTestCase {
 
     private LocalCheckpointTracker tracker;
 
-    private static final int SMALL_CHUNK_SIZE = 4;
-
     public static LocalCheckpointTracker createEmptyTracker() {
-        return new LocalCheckpointTracker(
-            IndexSettingsModule.newIndexSettings(
-                "test",
-                Settings
-                    .builder()
-                    .put(LocalCheckpointTracker.SETTINGS_BIT_ARRAYS_SIZE.getKey(), SMALL_CHUNK_SIZE)
-                    .build()),
-            SequenceNumbers.NO_OPS_PERFORMED,
-            SequenceNumbers.NO_OPS_PERFORMED
-        );
+        return new LocalCheckpointTracker(SequenceNumbers.NO_OPS_PERFORMED, SequenceNumbers.NO_OPS_PERFORMED);
     }
 
     @Override
@@ -98,7 +86,7 @@ public void testSimpleReplica() {
     public void testSimpleOverFlow() {
         List<Integer> seqNoList = new ArrayList<>();
         final boolean aligned = randomBoolean();
-        final int maxOps = SMALL_CHUNK_SIZE * randomIntBetween(1, 5) + (aligned ? 0 : randomIntBetween(1, SMALL_CHUNK_SIZE - 1));
+        final int maxOps = BIT_ARRAYS_SIZE * randomIntBetween(1, 5) + (aligned ? 0 : randomIntBetween(1, BIT_ARRAYS_SIZE - 1));
 
         for (int i = 0; i < maxOps; i++) {
             seqNoList.add(i);
@@ -109,7 +97,7 @@ public void testSimpleOverFlow() {
         }
         assertThat(tracker.checkpoint, equalTo(maxOps - 1L));
         assertThat(tracker.processedSeqNo.size(), equalTo(aligned ? 0 : 1));
-        assertThat(tracker.firstProcessedSeqNo, equalTo(((long) maxOps / SMALL_CHUNK_SIZE) * SMALL_CHUNK_SIZE));
+        assertThat(tracker.firstProcessedSeqNo, equalTo(((long) maxOps / BIT_ARRAYS_SIZE) * BIT_ARRAYS_SIZE));
     }
 
     public void testConcurrentPrimary() throws InterruptedException {
@@ -150,7 +138,7 @@ protected void doRun() throws Exception {
         tracker.markSeqNoAsCompleted(unFinishedSeq);
         assertThat(tracker.getCheckpoint(), equalTo(maxOps - 1L));
         assertThat(tracker.processedSeqNo.size(), isOneOf(0, 1));
-        assertThat(tracker.firstProcessedSeqNo, equalTo(((long) maxOps / SMALL_CHUNK_SIZE) * SMALL_CHUNK_SIZE));
+        assertThat(tracker.firstProcessedSeqNo, equalTo(((long) maxOps / BIT_ARRAYS_SIZE) * BIT_ARRAYS_SIZE));
     }
 
     public void testConcurrentReplica() throws InterruptedException {
@@ -198,7 +186,7 @@ protected void doRun() throws Exception {
         assertThat(tracker.getCheckpoint(), equalTo(unFinishedSeq - 1L));
         tracker.markSeqNoAsCompleted(unFinishedSeq);
         assertThat(tracker.getCheckpoint(), equalTo(maxOps - 1L));
-        assertThat(tracker.firstProcessedSeqNo, equalTo(((long) maxOps / SMALL_CHUNK_SIZE) * SMALL_CHUNK_SIZE));
+        assertThat(tracker.firstProcessedSeqNo, equalTo(((long) maxOps / BIT_ARRAYS_SIZE) * BIT_ARRAYS_SIZE));
     }
 
     public void testWaitForOpsToComplete() throws BrokenBarrierException, InterruptedException {