Prepare to make send translog of recovery non-blocking

server/src/main/java/org/elasticsearch/index/shard/IndexShard.java

@@ -2998,7 +2998,7 @@ public long getMaxSeqNoOfUpdatesOrDeletes() {
      * which is at least the value of the max_seq_no_of_updates marker on the primary after that operation was executed on the primary.
      *
      * @see #acquireReplicaOperationPermit(long, long, long, ActionListener, String, Object)
-     * @see org.elasticsearch.indices.recovery.RecoveryTarget#indexTranslogOperations(List, int, long, long)
+     * @see org.elasticsearch.indices.recovery.RecoveryTarget#indexTranslogOperations(List, int, long, long, ActionListener)
      */
     public void advanceMaxSeqNoOfUpdatesOrDeletes(long seqNo) {
         assert seqNo != UNASSIGNED_SEQ_NO

server/src/main/java/org/elasticsearch/indices/recovery/PeerRecoveryTargetService.java

@@ -485,14 +485,12 @@ class TranslogOperationsRequestHandler implements TransportRequestHandler<Recove
         public void messageReceived(final RecoveryTranslogOperationsRequest request, final TransportChannel channel,
                                     Task task) throws IOException {
             try (RecoveryRef recoveryRef =
-                         onGoingRecoveries.getRecoverySafe(request.recoveryId(), request.shardId())) {
+                     onGoingRecoveries.getRecoverySafe(request.recoveryId(), request.shardId())) {
                 final ClusterStateObserver observer = new ClusterStateObserver(clusterService, null, logger, threadPool.getThreadContext());
                 final RecoveryTarget recoveryTarget = recoveryRef.target();
-                try {
-                    recoveryTarget.indexTranslogOperations(request.operations(), request.totalTranslogOps(),
-                        request.maxSeenAutoIdTimestampOnPrimary(), request.maxSeqNoOfUpdatesOrDeletesOnPrimary());
-                    channel.sendResponse(new RecoveryTranslogOperationsResponse(recoveryTarget.indexShard().getLocalCheckpoint()));
-                } catch (MapperException exception) {
+                final ActionListener<RecoveryTranslogOperationsResponse> listener =
+                    new HandledTransportAction.ChannelActionListener<>(channel, Actions.TRANSLOG_OPS, request);
+                final Consumer<Exception> retryOnMappingException = exception -> {
                     // in very rare cases a translog replay from primary is processed before a mapping update on this node
                     // which causes local mapping changes since the mapping (clusterstate) might not have arrived on this node.
                     logger.debug("delaying recovery due to missing mapping changes", exception);
@@ -504,31 +502,36 @@ public void onNewClusterState(ClusterState state) {
                             try {
                                 messageReceived(request, channel, task);
                             } catch (Exception e) {
-                                onFailure(e);
-                            }
-                        }
-
-                        protected void onFailure(Exception e) {
-                            try {
-                                channel.sendResponse(e);
-                            } catch (IOException e1) {
-                                logger.warn("failed to send error back to recovery source", e1);
+                                listener.onFailure(e);
                             }
                         }
 
                         @Override
                         public void onClusterServiceClose() {
-                            onFailure(new ElasticsearchException("cluster service was closed while waiting for mapping updates"));
+                            listener.onFailure(new ElasticsearchException(
+                                "cluster service was closed while waiting for mapping updates"));
                         }
 
                         @Override
                         public void onTimeout(TimeValue timeout) {
                             // note that we do not use a timeout (see comment above)
-                            onFailure(new ElasticsearchTimeoutException("timed out waiting for mapping updates (timeout [" + timeout +
-                                    "])"));
+                            listener.onFailure(new ElasticsearchTimeoutException("timed out waiting for mapping updates " +
+                                "(timeout [" + timeout + "])"));
                         }
                     });
-                }
+                };
+                recoveryTarget.indexTranslogOperations(request.operations(), request.totalTranslogOps(),
+                    request.maxSeenAutoIdTimestampOnPrimary(), request.maxSeqNoOfUpdatesOrDeletesOnPrimary(),
+                    ActionListener.wrap(
+                        checkpoint -> listener.onResponse(new RecoveryTranslogOperationsResponse(checkpoint)),
+                        e -> {
+                            if (e instanceof MapperException) {
+                                retryOnMappingException.accept(e);
+                            } else {
+                                listener.onFailure(e);
+                            }
+                        })
+                );
             }
         }
     }

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

@@ -33,6 +33,7 @@
 import org.elasticsearch.Version;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.StepListener;
+import org.elasticsearch.action.support.PlainActionFuture;
 import org.elasticsearch.cluster.routing.IndexShardRoutingTable;
 import org.elasticsearch.cluster.routing.ShardRouting;
 import org.elasticsearch.common.StopWatch;
@@ -226,25 +227,27 @@ public void recoverToTarget(ActionListener<RecoveryResponse> listener) {
                 logger.trace("snapshot translog for recovery; current size is [{}]",
                     shard.estimateNumberOfHistoryOperations("peer-recovery", startingSeqNo));
             }
-            final SendSnapshotResult sendSnapshotResult;
-            try (Translog.Snapshot snapshot = shard.getHistoryOperations("peer-recovery", startingSeqNo)) {
-                // we can release the retention lock here because the snapshot itself will retain the required operations.
-                IOUtils.close(retentionLock, () -> resources.remove(retentionLock));
-                // we have to capture the max_seen_auto_id_timestamp and the max_seq_no_of_updates to make sure that these values
-                // are at least as high as the corresponding values on the primary when any of these operations were executed on it.
-                final long maxSeenAutoIdTimestamp = shard.getMaxSeenAutoIdTimestamp();
-                final long maxSeqNoOfUpdatesOrDeletes = shard.getMaxSeqNoOfUpdatesOrDeletes();
-                sendSnapshotResult = phase2(startingSeqNo, requiredSeqNoRangeStart, endingSeqNo, snapshot,
-                    maxSeenAutoIdTimestamp, maxSeqNoOfUpdatesOrDeletes);
-            } catch (Exception e) {
-                throw new RecoveryEngineException(shard.shardId(), 2, "phase2 failed", e);
-            }
 
+            final Translog.Snapshot phase2Snapshot = shard.getHistoryOperations("peer-recovery", startingSeqNo);
+            resources.add(phase2Snapshot);
+            // we can release the retention lock here because the snapshot itself will retain the required operations.
+            IOUtils.close(retentionLock);
+            // we have to capture the max_seen_auto_id_timestamp and the max_seq_no_of_updates to make sure that these values
+            // are at least as high as the corresponding values on the primary when any of these operations were executed on it.
+            final long maxSeenAutoIdTimestamp = shard.getMaxSeenAutoIdTimestamp();
+            final long maxSeqNoOfUpdatesOrDeletes = shard.getMaxSeqNoOfUpdatesOrDeletes();
+            final StepListener<SendSnapshotResult> sendSnapshotStep = new StepListener<>();
+            phase2(startingSeqNo, requiredSeqNoRangeStart, endingSeqNo, phase2Snapshot, maxSeenAutoIdTimestamp,
+                maxSeqNoOfUpdatesOrDeletes, sendSnapshotStep);
+            sendSnapshotStep.whenComplete(
+                r -> IOUtils.close(phase2Snapshot),
+                e -> onFailure.accept(new RecoveryEngineException(shard.shardId(), 2, "phase2 failed", e)));
             final StepListener<Void> finalizeStep = new StepListener<>();
-            finalizeRecovery(sendSnapshotResult.targetLocalCheckpoint, finalizeStep);
+            sendSnapshotStep.whenComplete(r -> finalizeRecovery(r.targetLocalCheckpoint, finalizeStep), onFailure);
+
             finalizeStep.whenComplete(r -> {
-                assert resources.isEmpty() : "not every resource is released [" + resources + "]";
                 final long phase1ThrottlingWaitTime = 0L; // TODO: return the actual throttle time
+                final SendSnapshotResult sendSnapshotResult = sendSnapshotStep.result();
                 final RecoveryResponse response = new RecoveryResponse(sendFileResult.phase1FileNames, sendFileResult.phase1FileSizes,
                     sendFileResult.phase1ExistingFileNames, sendFileResult.phase1ExistingFileSizes, sendFileResult.totalSize,
                     sendFileResult.existingTotalSize, sendFileResult.took.millis(), phase1ThrottlingWaitTime,
@@ -507,10 +510,17 @@ TimeValue prepareTargetForTranslog(final boolean fileBasedRecovery, final int to
      * @param snapshot                   a snapshot of the translog
      * @param maxSeenAutoIdTimestamp     the max auto_id_timestamp of append-only requests on the primary
      * @param maxSeqNoOfUpdatesOrDeletes the max seq_no of updates or deletes on the primary after these operations were executed on it.
-     * @return the send snapshot result
+     * @param listener                   a listener which will be notified with the local checkpoint on the target.
      */
-    SendSnapshotResult phase2(long startingSeqNo, long requiredSeqNoRangeStart, long endingSeqNo, Translog.Snapshot snapshot,
-                              long maxSeenAutoIdTimestamp, long maxSeqNoOfUpdatesOrDeletes) throws IOException {
+    void phase2(long startingSeqNo, long requiredSeqNoRangeStart, long endingSeqNo, Translog.Snapshot snapshot, long maxSeenAutoIdTimestamp,
+                long maxSeqNoOfUpdatesOrDeletes, ActionListener<SendSnapshotResult> listener) throws IOException {
+        ActionListener.completeWith(listener, () -> sendSnapshotBlockingly(
+            startingSeqNo, requiredSeqNoRangeStart, endingSeqNo, snapshot, maxSeenAutoIdTimestamp, maxSeqNoOfUpdatesOrDeletes));
+    }
+
+    private SendSnapshotResult sendSnapshotBlockingly(long startingSeqNo, long requiredSeqNoRangeStart, long endingSeqNo,
+                                                      Translog.Snapshot snapshot, long maxSeenAutoIdTimestamp,
+                                                      long maxSeqNoOfUpdatesOrDeletes) throws IOException {
         assert requiredSeqNoRangeStart <= endingSeqNo + 1:
             "requiredSeqNoRangeStart " + requiredSeqNoRangeStart + " is larger than endingSeqNo " + endingSeqNo;
         assert startingSeqNo <= requiredSeqNoRangeStart :
@@ -538,9 +548,11 @@ SendSnapshotResult phase2(long startingSeqNo, long requiredSeqNoRangeStart, long
         }
 
         final CancellableThreads.IOInterruptible sendBatch = () -> {
-            final long targetCheckpoint = recoveryTarget.indexTranslogOperations(
-                operations, expectedTotalOps, maxSeenAutoIdTimestamp, maxSeqNoOfUpdatesOrDeletes);
-            targetLocalCheckpoint.set(targetCheckpoint);
+            // TODO: Make this non-blocking
+            final PlainActionFuture<Long> future = new PlainActionFuture<>();
+            recoveryTarget.indexTranslogOperations(
+                operations, expectedTotalOps, maxSeenAutoIdTimestamp, maxSeqNoOfUpdatesOrDeletes, future);
+            targetLocalCheckpoint.set(future.actionGet());
         };
 
         // send operations in batches

server/src/main/java/org/elasticsearch/indices/recovery/RecoveryTarget.java

@@ -394,40 +394,42 @@ public void handoffPrimaryContext(final ReplicationTracker.PrimaryContext primar
     }
 
     @Override
-    public long indexTranslogOperations(List<Translog.Operation> operations, int totalTranslogOps, long maxSeenAutoIdTimestampOnPrimary,
-                                        long maxSeqNoOfDeletesOrUpdatesOnPrimary) throws IOException {
-        final RecoveryState.Translog translog = state().getTranslog();
-        translog.totalOperations(totalTranslogOps);
-        assert indexShard().recoveryState() == state();
-        if (indexShard().state() != IndexShardState.RECOVERING) {
-            throw new IndexShardNotRecoveringException(shardId, indexShard().state());
-        }
-        /*
-         * The maxSeenAutoIdTimestampOnPrimary received from the primary is at least the highest auto_id_timestamp from any operation
-         * will be replayed. Bootstrapping this timestamp here will disable the optimization for original append-only requests
-         * (source of these operations) replicated via replication. Without this step, we may have duplicate documents if we
-         * replay these operations first (without timestamp), then optimize append-only requests (with timestamp).
-         */
-        indexShard().updateMaxUnsafeAutoIdTimestamp(maxSeenAutoIdTimestampOnPrimary);
-        /*
-         * Bootstrap the max_seq_no_of_updates from the primary to make sure that the max_seq_no_of_updates on this replica when
-         * replaying any of these operations will be at least the max_seq_no_of_updates on the primary when that operation was executed on.
-         */
-        indexShard().advanceMaxSeqNoOfUpdatesOrDeletes(maxSeqNoOfDeletesOrUpdatesOnPrimary);
-        for (Translog.Operation operation : operations) {
-            Engine.Result result = indexShard().applyTranslogOperation(operation, Engine.Operation.Origin.PEER_RECOVERY);
-            if (result.getResultType() == Engine.Result.Type.MAPPING_UPDATE_REQUIRED) {
-                throw new MapperException("mapping updates are not allowed [" + operation + "]");
+    public void indexTranslogOperations(List<Translog.Operation> operations, int totalTranslogOps, long maxSeenAutoIdTimestampOnPrimary,
+                                        long maxSeqNoOfDeletesOrUpdatesOnPrimary, ActionListener<Long> listener) {
+        ActionListener.completeWith(listener, () -> {
+            final RecoveryState.Translog translog = state().getTranslog();
+            translog.totalOperations(totalTranslogOps);
+            assert indexShard().recoveryState() == state();
+            if (indexShard().state() != IndexShardState.RECOVERING) {
+                throw new IndexShardNotRecoveringException(shardId, indexShard().state());
             }
-            assert result.getFailure() == null: "unexpected failure while replicating translog entry: " + result.getFailure();
-            ExceptionsHelper.reThrowIfNotNull(result.getFailure());
-        }
-        // update stats only after all operations completed (to ensure that mapping updates don't mess with stats)
-        translog.incrementRecoveredOperations(operations.size());
-        indexShard().sync();
-        // roll over / flush / trim if needed
-        indexShard().afterWriteOperation();
-        return indexShard().getLocalCheckpoint();
+            /*
+             * The maxSeenAutoIdTimestampOnPrimary received from the primary is at least the highest auto_id_timestamp from any operation
+             * will be replayed. Bootstrapping this timestamp here will disable the optimization for original append-only requests
+             * (source of these operations) replicated via replication. Without this step, we may have duplicate documents if we
+             * replay these operations first (without timestamp), then optimize append-only requests (with timestamp).
+             */
+            indexShard().updateMaxUnsafeAutoIdTimestamp(maxSeenAutoIdTimestampOnPrimary);
+            /*
+             * Bootstrap the max_seq_no_of_updates from the primary to make sure that the max_seq_no_of_updates on this replica when
+             * replaying any of these operations will be at least the max_seq_no_of_updates on the primary when that op was executed on.
+             */
+            indexShard().advanceMaxSeqNoOfUpdatesOrDeletes(maxSeqNoOfDeletesOrUpdatesOnPrimary);
+            for (Translog.Operation operation : operations) {
+                Engine.Result result = indexShard().applyTranslogOperation(operation, Engine.Operation.Origin.PEER_RECOVERY);
+                if (result.getResultType() == Engine.Result.Type.MAPPING_UPDATE_REQUIRED) {
+                    throw new MapperException("mapping updates are not allowed [" + operation + "]");
+                }
+                assert result.getFailure() == null : "unexpected failure while replicating translog entry: " + result.getFailure();
+                ExceptionsHelper.reThrowIfNotNull(result.getFailure());
+            }
+            // update stats only after all operations completed (to ensure that mapping updates don't mess with stats)
+            translog.incrementRecoveredOperations(operations.size());
+            indexShard().sync();
+            // roll over / flush / trim if needed
+            indexShard().afterWriteOperation();
+            return indexShard().getLocalCheckpoint();
+        });
     }
 
     @Override

server/src/main/java/org/elasticsearch/indices/recovery/RecoveryTargetHandler.java

@@ -67,10 +67,11 @@ public interface RecoveryTargetHandler {
      * @param maxSeqNoOfUpdatesOrDeletesOnPrimary the max seq_no of update operations (index operations overwrite Lucene) or delete ops on
      *                                            the primary shard when capturing these operations. This value is at least as high as the
      *                                            max_seq_no_of_updates on the primary was when any of these ops were processed on it.
-     * @return the local checkpoint on the target shard
+     * @param listener                            a listener which will be notified with the local checkpoint on the target
+     *                                            after these operations are successfully indexed on the target.
      */
-    long indexTranslogOperations(List<Translog.Operation> operations, int totalTranslogOps,
-                                 long maxSeenAutoIdTimestampOnPrimary, long maxSeqNoOfUpdatesOrDeletesOnPrimary) throws IOException;
+    void indexTranslogOperations(List<Translog.Operation> operations, int totalTranslogOps, long maxSeenAutoIdTimestampOnPrimary,
+                                 long maxSeqNoOfUpdatesOrDeletesOnPrimary, ActionListener<Long> listener);
 
     /**
      * Notifies the target of the files it is going to receive