Fix file reading in ccr restore service (#38117)

Currently we use the raw byte array length when calling the IndexInput
read call to determine how many bytes we want to read. However, due to
how BigArrays works, the array length might be longer than the reference
length. This commit fixes the issue and uses the BytesRef length when
calling read. Additionally, it expands the index follow test to index
many more documents. These documents should potentially lead to large
enough segment files to trigger scenarios where this fix matters.

Author: Tim-Brooks

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/repository/CcrRestoreSourceService.java

@@ -235,8 +235,7 @@ private long readFileBytes(String fileName, BytesReference reference) throws IOE
                 BytesRefIterator refIterator = reference.iterator();
                 BytesRef ref;
                 while ((ref = refIterator.next()) != null) {
-                    byte[] refBytes = ref.bytes;
-                    indexInput.readBytes(refBytes, 0, refBytes.length);
+                    indexInput.readBytes(ref.bytes, ref.offset, ref.length);
                 }
 
                 long offsetAfterRead = indexInput.getFilePointer();

x-pack/plugin/ccr/src/test/java/org/elasticsearch/xpack/CcrIntegTestCase.java

@@ -70,7 +70,6 @@
 import org.elasticsearch.transport.nio.MockNioTransportPlugin;
 import org.elasticsearch.xpack.ccr.CcrSettings;
 import org.elasticsearch.xpack.ccr.LocalStateCcr;
-import org.elasticsearch.xpack.ccr.index.engine.FollowingEngine;
 import org.elasticsearch.xpack.core.XPackSettings;
 import org.elasticsearch.xpack.core.ccr.AutoFollowMetadata;
 import org.elasticsearch.xpack.core.ccr.ShardFollowNodeTaskStatus;
@@ -551,27 +550,6 @@ protected void assertMaxSeqNoOfUpdatesIsTransferred(Index leaderIndex, Index fol
         });
     }
 
-    protected void assertTotalNumberOfOptimizedIndexing(Index followerIndex, int numberOfShards, long expectedTotal) throws Exception {
-        assertBusy(() -> {
-            long[] numOfOptimizedOps = new long[numberOfShards];
-            for (int shardId = 0; shardId < numberOfShards; shardId++) {
-                for (String node : getFollowerCluster().nodesInclude(followerIndex.getName())) {
-                    IndicesService indicesService = getFollowerCluster().getInstance(IndicesService.class, node);
-                    IndexShard shard = indicesService.getShardOrNull(new ShardId(followerIndex, shardId));
-                    if (shard != null && shard.routingEntry().primary()) {
-                        try {
-                            FollowingEngine engine = ((FollowingEngine) IndexShardTestCase.getEngine(shard));
-                            numOfOptimizedOps[shardId] = engine.getNumberOfOptimizedIndexing();
-                        } catch (AlreadyClosedException e) {
-                            throw new AssertionError(e); // causes assertBusy to retry
-                        }
-                    }
-                }
-            }
-            assertThat(Arrays.stream(numOfOptimizedOps).sum(), equalTo(expectedTotal));
-        });
-    }
-
     static void removeCCRRelatedMetadataFromClusterState(ClusterService clusterService) throws Exception {
         CountDownLatch latch = new CountDownLatch(1);
         clusterService.submitStateUpdateTask("remove-ccr-related-metadata", new ClusterStateUpdateTask() {

x-pack/plugin/ccr/src/test/java/org/elasticsearch/xpack/ccr/IndexFollowingIT.java

@@ -26,6 +26,7 @@
 import org.elasticsearch.action.admin.indices.stats.ShardStats;
 import org.elasticsearch.action.bulk.BulkProcessor;
 import org.elasticsearch.action.bulk.BulkRequest;
+import org.elasticsearch.action.bulk.BulkRequestBuilder;
 import org.elasticsearch.action.bulk.BulkResponse;
 import org.elasticsearch.action.get.GetResponse;
 import org.elasticsearch.action.index.IndexRequest;
@@ -101,9 +102,30 @@ public void testFollowIndex() throws Exception {
         assertAcked(leaderClient().admin().indices().prepareCreate("index1").setSource(leaderIndexSettings, XContentType.JSON));
         ensureLeaderYellow("index1");
 
-        final int firstBatchNumDocs = randomIntBetween(2, 64);
+        final int firstBatchNumDocs;
+        // Sometimes we want to index a lot of documents to ensure that the recovery works with larger files
+        if (rarely()) {
+            firstBatchNumDocs = randomIntBetween(1800, 2000);
+        } else {
+            firstBatchNumDocs = randomIntBetween(10, 64);
+        }
+        final int flushPoint = (int) (firstBatchNumDocs * 0.75);
+
         logger.info("Indexing [{}] docs as first batch", firstBatchNumDocs);
-        for (int i = 0; i < firstBatchNumDocs; i++) {
+        BulkRequestBuilder bulkRequestBuilder = leaderClient().prepareBulk();
+        for (int i = 0; i < flushPoint; i++) {
+            final String source = String.format(Locale.ROOT, "{\"f\":%d}", i);
+            IndexRequest indexRequest = new IndexRequest("index1", "doc", Integer.toString(i))
+                .source(source, XContentType.JSON)
+                .timeout(TimeValue.timeValueSeconds(1));
+            bulkRequestBuilder.add(indexRequest);
+        }
+        bulkRequestBuilder.get();
+
+        leaderClient().admin().indices().prepareFlush("index1").setWaitIfOngoing(true).get();
+
+        // Index some docs after the flush that might be recovered in the normal index following operations
+        for (int i = flushPoint; i < firstBatchNumDocs; i++) {
             final String source = String.format(Locale.ROOT, "{\"f\":%d}", i);
             leaderClient().prepareIndex("index1", "doc", Integer.toString(i)).setSource(source, XContentType.JSON).get();
         }
@@ -147,7 +169,7 @@ public void testFollowIndex() throws Exception {
         for (int i = 0; i < firstBatchNumDocs; i++) {
             assertBusy(assertExpectedDocumentRunnable(i));
         }
-        assertTotalNumberOfOptimizedIndexing(resolveFollowerIndex("index2"), numberOfPrimaryShards, firstBatchNumDocs);
+
         pauseFollow("index2");
         followerClient().execute(ResumeFollowAction.INSTANCE, followRequest.getFollowRequest()).get();
         final int secondBatchNumDocs = randomIntBetween(2, 64);
@@ -172,8 +194,6 @@ public void testFollowIndex() throws Exception {
         for (int i = firstBatchNumDocs; i < firstBatchNumDocs + secondBatchNumDocs; i++) {
             assertBusy(assertExpectedDocumentRunnable(i));
         }
-        assertTotalNumberOfOptimizedIndexing(resolveFollowerIndex("index2"), numberOfPrimaryShards,
-            firstBatchNumDocs + secondBatchNumDocs);
         pauseFollow("index2");
         assertMaxSeqNoOfUpdatesIsTransferred(resolveLeaderIndex("index1"), resolveFollowerIndex("index2"), numberOfPrimaryShards);
     }
@@ -287,7 +307,6 @@ public void testFollowIndexWithoutWaitForComplete() throws Exception {
         for (int i = 0; i < firstBatchNumDocs; i++) {
             assertBusy(assertExpectedDocumentRunnable(i));
         }
-        assertTotalNumberOfOptimizedIndexing(resolveFollowerIndex("index2"), numberOfPrimaryShards, firstBatchNumDocs);
         pauseFollow("index2");
     }
 
@@ -432,8 +451,6 @@ public void afterBulk(long executionId, BulkRequest request, Throwable failure)
         assertIndexFullyReplicatedToFollower("index1", "index2");
         pauseFollow("index2");
         leaderClient().admin().indices().prepareRefresh("index1").get();
-        assertTotalNumberOfOptimizedIndexing(resolveFollowerIndex("index2"), numberOfShards,
-            leaderClient().prepareSearch("index1").get().getHits().getTotalHits().value);
         assertMaxSeqNoOfUpdatesIsTransferred(resolveLeaderIndex("index1"), resolveFollowerIndex("index2"), numberOfShards);
     }
 
@@ -475,7 +492,6 @@ public void testFollowIndexWithNestedField() throws Exception {
         }
         pauseFollow("index2");
         assertMaxSeqNoOfUpdatesIsTransferred(resolveLeaderIndex("index1"), resolveFollowerIndex("index2"), 1);
-        assertTotalNumberOfOptimizedIndexing(resolveFollowerIndex("index2"), 1, numDocs);
     }
 
     public void testUnfollowNonExistingIndex() {
@@ -538,7 +554,6 @@ public void testFollowIndexMaxOperationSizeInBytes() throws Exception {
         }
         pauseFollow("index2");
         assertMaxSeqNoOfUpdatesIsTransferred(resolveLeaderIndex("index1"), resolveFollowerIndex("index2"), 1);
-        assertTotalNumberOfOptimizedIndexing(resolveFollowerIndex("index2"), 1, numDocs);
     }
 
     public void testAttemptToChangeCcrFollowingIndexSetting() throws Exception {