Enable trace log in FollowerFailOverIT (#38148)

This suite still fails one per week sometimes with a worrying assertion.
Sadly we are still unable to find the actual source.

Expected: <SeqNoStats{maxSeqNo=229, localCheckpoint=86, globalCheckpoint=86}>
but: was   <SeqNoStats{maxSeqNo=229, localCheckpoint=-1, globalCheckpoint=86}>

This change enables trace log in the suite so we will have a better
picture if this fails again.

Relates #3333

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/action/bulk/TransportBulkShardOperationsAction.java

@@ -63,6 +63,9 @@ public TransportBulkShardOperationsAction(
     @Override
     protected WritePrimaryResult<BulkShardOperationsRequest, BulkShardOperationsResponse> shardOperationOnPrimary(
             final BulkShardOperationsRequest request, final IndexShard primary) throws Exception {
+        if (logger.isTraceEnabled()) {
+            logger.trace("index [{}] on the following primary shard {}", request.getOperations(), primary.routingEntry());
+        }
         return shardOperationOnPrimary(request.shardId(), request.getHistoryUUID(), request.getOperations(),
             request.getMaxSeqNoOfUpdatesOrDeletes(), primary, logger);
     }
@@ -137,6 +140,10 @@ public static CcrWritePrimaryResult shardOperationOnPrimary(
                     // replicated to replicas but with the existing primary term (not the current primary term) in order
                     // to guarantee the consistency between the primary and replicas, and between translog and Lucene index.
                     final AlreadyProcessedFollowingEngineException failure = (AlreadyProcessedFollowingEngineException) result.getFailure();
+                    if (logger.isTraceEnabled()) {
+                        logger.trace("operation [{}] was processed before on following primary shard {} with existing term {}",
+                            targetOp, primary.routingEntry(), failure.getExistingPrimaryTerm());
+                    }
                     assert failure.getSeqNo() == targetOp.seqNo() : targetOp.seqNo() + " != " + failure.getSeqNo();
                     if (failure.getExistingPrimaryTerm().isPresent()) {
                         appliedOperations.add(rewriteOperationWithPrimaryTerm(sourceOp, failure.getExistingPrimaryTerm().getAsLong()));
@@ -159,6 +166,9 @@ public static CcrWritePrimaryResult shardOperationOnPrimary(
     @Override
     protected WriteReplicaResult<BulkShardOperationsRequest> shardOperationOnReplica(
             final BulkShardOperationsRequest request, final IndexShard replica) throws Exception {
+        if (logger.isTraceEnabled()) {
+            logger.trace("index [{}] on the following replica shard {}", request.getOperations(), replica.routingEntry());
+        }
         return shardOperationOnReplica(request, replica, logger);
     }
 

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/index/engine/FollowingEngine.java

@@ -72,6 +72,9 @@ protected InternalEngine.IndexingStrategy indexingStrategyForOperation(final Ind
         final long maxSeqNoOfUpdatesOrDeletes = getMaxSeqNoOfUpdatesOrDeletes();
         assert maxSeqNoOfUpdatesOrDeletes != SequenceNumbers.UNASSIGNED_SEQ_NO : "max_seq_no_of_updates is not initialized";
         if (hasBeenProcessedBefore(index)) {
+            if (logger.isTraceEnabled()) {
+                logger.trace("index operation [id={} seq_no={} origin={}] was processed before", index.id(), index.seqNo(), index.origin());
+            }
             if (index.origin() == Operation.Origin.PRIMARY) {
                 /*
                  * The existing operation in this engine was probably assigned the term of the previous primary shard which is different

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

@@ -447,6 +447,13 @@ public static ResumeFollowAction.Request resumeFollow(String followerIndex) {
      * on the follower equal the leader's; then verifies the existing pairs of (docId, seqNo) on the follower also equal the leader.
      */
     protected void assertIndexFullyReplicatedToFollower(String leaderIndex, String followerIndex) throws Exception {
+        logger.info("--> asserting <<docId,seqNo>> between {} and {}", leaderIndex, followerIndex);
+        assertBusy(() -> {
+            Map<Integer, List<DocIdSeqNoAndTerm>> docsOnFollower = getDocIdAndSeqNos(clusterGroup.followerCluster, followerIndex);
+            logger.info("--> docs on the follower {}", docsOnFollower);
+            assertThat(docsOnFollower, equalTo(getDocIdAndSeqNos(clusterGroup.leaderCluster, leaderIndex)));
+        }, 120, TimeUnit.SECONDS);
+
         logger.info("--> asserting seq_no_stats between {} and {}", leaderIndex, followerIndex);
         assertBusy(() -> {
             Map<Integer, SeqNoStats> leaderStats = new HashMap<>();
@@ -463,13 +470,8 @@ protected void assertIndexFullyReplicatedToFollower(String leaderIndex, String f
                 }
                 followerStats.put(shardStat.getShardRouting().shardId().id(), shardStat.getSeqNoStats());
             }
-            assertThat(leaderStats, equalTo(followerStats));
-        }, 60, TimeUnit.SECONDS);
-        logger.info("--> asserting <<docId,seqNo>> between {} and {}", leaderIndex, followerIndex);
-        assertBusy(() -> {
-            assertThat(getDocIdAndSeqNos(clusterGroup.leaderCluster, leaderIndex),
-                equalTo(getDocIdAndSeqNos(clusterGroup.followerCluster, followerIndex)));
-        }, 60, TimeUnit.SECONDS);
+            assertThat(followerStats, equalTo(leaderStats));
+        }, 120, TimeUnit.SECONDS);
     }
 
     private Map<Integer, List<DocIdSeqNoAndTerm>> getDocIdAndSeqNos(InternalTestCluster cluster, String index) throws IOException {

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

@@ -27,6 +27,7 @@
 import org.elasticsearch.index.shard.ShardId;
 import org.elasticsearch.indices.IndicesService;
 import org.elasticsearch.test.InternalTestCluster;
+import org.elasticsearch.test.junit.annotations.TestLogging;
 import org.elasticsearch.xpack.CcrIntegTestCase;
 import org.elasticsearch.xpack.core.ccr.action.FollowStatsAction;
 import org.elasticsearch.xpack.core.ccr.action.PutFollowAction;
@@ -44,6 +45,7 @@
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
 import static org.hamcrest.Matchers.equalTo;
 
+@TestLogging("org.elasticsearch.xpack.ccr:TRACE,org.elasticsearch.index.shard:DEBUG")
 public class FollowerFailOverIT extends CcrIntegTestCase {
 
     @Override