Simplify code using Java 8 features
[controller.git] / opendaylight / md-sal / sal-distributed-datastore / src / main / java / org / opendaylight / controller / cluster / sharding / DistributedShardedDOMDataTree.java
index 557543803769413e0baaebb73c1eae218293ba1e..64c3f14dfb5dde59806c31dd3f92e92af745ebc7 100644 (file)
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016 Cisco Systems, Inc. and others.  All rights reserved.
+ * Copyright (c) 2016, 2017 Cisco Systems, Inc. and others.  All rights reserved.
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
@@ -14,35 +14,60 @@ import akka.actor.ActorRef;
 import akka.actor.ActorSystem;
 import akka.actor.PoisonPill;
 import akka.actor.Props;
-import akka.cluster.Cluster;
-import akka.cluster.Member;
+import akka.dispatch.Mapper;
+import akka.dispatch.OnComplete;
+import akka.pattern.Patterns;
 import akka.util.Timeout;
+import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
 import com.google.common.base.Throwables;
-import com.google.common.collect.Collections2;
+import com.google.common.collect.ClassToInstanceMap;
 import com.google.common.collect.ForwardingObject;
+import com.google.common.collect.ImmutableClassToInstanceMap;
+import com.google.common.util.concurrent.FutureCallback;
+import com.google.common.util.concurrent.Futures;
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.MoreExecutors;
+import com.google.common.util.concurrent.SettableFuture;
 import com.google.common.util.concurrent.Uninterruptibles;
 import java.util.AbstractMap.SimpleEntry;
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Comparator;
 import java.util.EnumMap;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
+import java.util.concurrent.CompletionStage;
+import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
+import org.opendaylight.controller.cluster.ActorSystemProvider;
 import org.opendaylight.controller.cluster.access.concepts.MemberName;
 import org.opendaylight.controller.cluster.databroker.actors.dds.DataStoreClient;
 import org.opendaylight.controller.cluster.databroker.actors.dds.SimpleDataStoreClientActor;
-import org.opendaylight.controller.cluster.datastore.DistributedDataStore;
-import org.opendaylight.controller.cluster.datastore.config.PrefixShardConfiguration;
+import org.opendaylight.controller.cluster.datastore.AbstractDataStore;
+import org.opendaylight.controller.cluster.datastore.Shard;
+import org.opendaylight.controller.cluster.datastore.config.Configuration;
+import org.opendaylight.controller.cluster.datastore.config.ModuleShardConfiguration;
+import org.opendaylight.controller.cluster.datastore.messages.CreateShard;
+import org.opendaylight.controller.cluster.datastore.shardstrategy.ModuleShardStrategy;
 import org.opendaylight.controller.cluster.datastore.utils.ActorContext;
 import org.opendaylight.controller.cluster.datastore.utils.ClusterUtils;
+import org.opendaylight.controller.cluster.dom.api.CDSDataTreeProducer;
+import org.opendaylight.controller.cluster.dom.api.CDSShardAccess;
 import org.opendaylight.controller.cluster.sharding.ShardedDataTreeActor.ShardedDataTreeActorCreator;
-import org.opendaylight.controller.cluster.sharding.messages.CreatePrefixShard;
+import org.opendaylight.controller.cluster.sharding.messages.InitConfigListener;
+import org.opendaylight.controller.cluster.sharding.messages.LookupPrefixShard;
+import org.opendaylight.controller.cluster.sharding.messages.PrefixShardRemovalLookup;
 import org.opendaylight.controller.cluster.sharding.messages.ProducerCreated;
 import org.opendaylight.controller.cluster.sharding.messages.ProducerRemoved;
-import org.opendaylight.controller.cluster.sharding.messages.RemovePrefixShard;
+import org.opendaylight.controller.cluster.sharding.messages.StartConfigShardLookup;
 import org.opendaylight.mdsal.common.api.LogicalDatastoreType;
 import org.opendaylight.mdsal.dom.api.DOMDataTreeCursorAwareTransaction;
 import org.opendaylight.mdsal.dom.api.DOMDataTreeIdentifier;
@@ -51,6 +76,7 @@ import org.opendaylight.mdsal.dom.api.DOMDataTreeLoopException;
 import org.opendaylight.mdsal.dom.api.DOMDataTreeProducer;
 import org.opendaylight.mdsal.dom.api.DOMDataTreeProducerException;
 import org.opendaylight.mdsal.dom.api.DOMDataTreeService;
+import org.opendaylight.mdsal.dom.api.DOMDataTreeServiceExtension;
 import org.opendaylight.mdsal.dom.api.DOMDataTreeShard;
 import org.opendaylight.mdsal.dom.api.DOMDataTreeShardingConflictException;
 import org.opendaylight.mdsal.dom.api.DOMDataTreeShardingService;
@@ -58,11 +84,15 @@ import org.opendaylight.mdsal.dom.broker.DOMDataTreeShardRegistration;
 import org.opendaylight.mdsal.dom.broker.ShardedDOMDataTree;
 import org.opendaylight.mdsal.dom.spi.DOMDataTreePrefixTable;
 import org.opendaylight.mdsal.dom.spi.DOMDataTreePrefixTableEntry;
+import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.controller.md.sal.clustering.prefix.shard.configuration.rev170110.PrefixShards;
 import org.opendaylight.yangtools.concepts.ListenerRegistration;
 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import scala.collection.JavaConverters;
+import scala.compat.java8.FutureConverters;
+import scala.concurrent.Future;
+import scala.concurrent.Promise;
+import scala.concurrent.duration.FiniteDuration;
 
 /**
  * A layer on top of DOMDataTreeService that distributes producer/shard registrations to remote nodes via
@@ -73,31 +103,40 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
 
     private static final Logger LOG = LoggerFactory.getLogger(DistributedShardedDOMDataTree.class);
 
-    private static final Timeout DEFAULT_ASK_TIMEOUT = new Timeout(15, TimeUnit.SECONDS);
     private static final int MAX_ACTOR_CREATION_RETRIES = 100;
     private static final int ACTOR_RETRY_DELAY = 100;
     private static final TimeUnit ACTOR_RETRY_TIME_UNIT = TimeUnit.MILLISECONDS;
+    private static final int LOOKUP_TASK_MAX_RETRIES = 100;
+    static final FiniteDuration SHARD_FUTURE_TIMEOUT_DURATION =
+            new FiniteDuration(LOOKUP_TASK_MAX_RETRIES * LOOKUP_TASK_MAX_RETRIES * 3, TimeUnit.SECONDS);
+    static final Timeout SHARD_FUTURE_TIMEOUT = new Timeout(SHARD_FUTURE_TIMEOUT_DURATION);
 
     static final String ACTOR_ID = "ShardedDOMDataTreeFrontend";
 
     private final ShardedDOMDataTree shardedDOMDataTree;
     private final ActorSystem actorSystem;
-    private final DistributedDataStore distributedOperDatastore;
-    private final DistributedDataStore distributedConfigDatastore;
+    private final AbstractDataStore distributedOperDatastore;
+    private final AbstractDataStore distributedConfigDatastore;
 
     private final ActorRef shardedDataTreeActor;
     private final MemberName memberName;
 
+    @GuardedBy("shards")
     private final DOMDataTreePrefixTable<DOMDataTreeShardRegistration<DOMDataTreeShard>> shards =
             DOMDataTreePrefixTable.create();
 
-    private final EnumMap<LogicalDatastoreType, DistributedShardRegistration> defaultShardRegistrations =
+    private final EnumMap<LogicalDatastoreType, Entry<DataStoreClient, ActorRef>> configurationShardMap =
             new EnumMap<>(LogicalDatastoreType.class);
 
-    public DistributedShardedDOMDataTree(final ActorSystem actorSystem,
-                                         final DistributedDataStore distributedOperDatastore,
-                                         final DistributedDataStore distributedConfigDatastore) {
-        this.actorSystem = Preconditions.checkNotNull(actorSystem);
+    private final EnumMap<LogicalDatastoreType, PrefixedShardConfigWriter> writerMap =
+            new EnumMap<>(LogicalDatastoreType.class);
+
+    private final PrefixedShardConfigUpdateHandler updateHandler;
+
+    public DistributedShardedDOMDataTree(final ActorSystemProvider actorSystemProvider,
+                                         final AbstractDataStore distributedOperDatastore,
+                                         final AbstractDataStore distributedConfigDatastore) {
+        this.actorSystem = Preconditions.checkNotNull(actorSystemProvider).getActorSystem();
         this.distributedOperDatastore = Preconditions.checkNotNull(distributedOperDatastore);
         this.distributedConfigDatastore = Preconditions.checkNotNull(distributedConfigDatastore);
         shardedDOMDataTree = new ShardedDOMDataTree();
@@ -108,25 +147,127 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
                         .setActorSystem(actorSystem)
                         .setClusterWrapper(distributedConfigDatastore.getActorContext().getClusterWrapper())
                         .setDistributedConfigDatastore(distributedConfigDatastore)
-                        .setDistributedOperDatastore(distributedOperDatastore),
+                        .setDistributedOperDatastore(distributedOperDatastore)
+                        .setLookupTaskMaxRetries(LOOKUP_TASK_MAX_RETRIES),
                 ACTOR_ID);
 
         this.memberName = distributedConfigDatastore.getActorContext().getCurrentMemberName();
 
-        //create shard registration for DEFAULT_SHARD
+        updateHandler = new PrefixedShardConfigUpdateHandler(shardedDataTreeActor,
+                distributedConfigDatastore.getActorContext().getCurrentMemberName());
+
+        LOG.debug("{} - Starting prefix configuration shards", memberName);
+        createPrefixConfigShard(distributedConfigDatastore);
+        createPrefixConfigShard(distributedOperDatastore);
+    }
+
+    private static void createPrefixConfigShard(final AbstractDataStore dataStore) {
+        Configuration configuration = dataStore.getActorContext().getConfiguration();
+        Collection<MemberName> memberNames = configuration.getUniqueMemberNamesForAllShards();
+        CreateShard createShardMessage =
+                new CreateShard(new ModuleShardConfiguration(PrefixShards.QNAME.getNamespace(),
+                        "prefix-shard-configuration", ClusterUtils.PREFIX_CONFIG_SHARD_ID, ModuleShardStrategy.NAME,
+                        memberNames),
+                        Shard.builder(), dataStore.getActorContext().getDatastoreContext());
+
+        dataStore.getActorContext().getShardManager().tell(createShardMessage, noSender());
+    }
+
+    /**
+     * This will try to initialize prefix configuration shards upon their
+     * successful start. We need to create writers to these shards, so we can
+     * satisfy future {@link #createDistributedShard} and
+     * {@link #resolveShardAdditions} requests and update prefix configuration
+     * shards accordingly.
+     *
+     * <p>
+     * We also need to initialize listeners on these shards, so we can react
+     * on changes made on them by other cluster members or even by ourselves.
+     *
+     * <p>
+     * Finally, we need to be sure that default shards for both operational and
+     * configuration data stores are up and running and we have distributed
+     * shards frontend created for them.
+     *
+     * <p>
+     * This is intended to be invoked by blueprint as initialization method.
+     */
+    public void init() {
+        // create our writers to the configuration
         try {
-            defaultShardRegistrations.put(LogicalDatastoreType.CONFIGURATION,
-                    initDefaultShard(LogicalDatastoreType.CONFIGURATION));
-        } catch (final DOMDataTreeProducerException | DOMDataTreeShardingConflictException e) {
-            LOG.error("Unable to create default shard frontend for config shard", e);
+            LOG.debug("{} - starting config shard lookup.", memberName);
+
+            // We have to wait for prefix config shards to be up and running
+            // so we can create datastore clients for them
+            handleConfigShardLookup().get(SHARD_FUTURE_TIMEOUT_DURATION.length(), SHARD_FUTURE_TIMEOUT_DURATION.unit());
+        } catch (InterruptedException | ExecutionException | TimeoutException e) {
+            throw new IllegalStateException("Prefix config shards not found", e);
         }
 
         try {
-            defaultShardRegistrations.put(LogicalDatastoreType.OPERATIONAL,
-                    initDefaultShard(LogicalDatastoreType.OPERATIONAL));
-        } catch (final DOMDataTreeProducerException | DOMDataTreeShardingConflictException e) {
-            LOG.error("Unable to create default shard frontend for operational shard", e);
+            LOG.debug("{}: Prefix configuration shards ready - creating clients", memberName);
+            configurationShardMap.put(LogicalDatastoreType.CONFIGURATION,
+                    createDatastoreClient(ClusterUtils.PREFIX_CONFIG_SHARD_ID,
+                            distributedConfigDatastore.getActorContext()));
+        } catch (final DOMDataTreeShardCreationFailedException e) {
+            throw new IllegalStateException(
+                    "Unable to create datastoreClient for config DS prefix configuration shard.", e);
+        }
+
+        try {
+            configurationShardMap.put(LogicalDatastoreType.OPERATIONAL,
+                    createDatastoreClient(ClusterUtils.PREFIX_CONFIG_SHARD_ID,
+                            distributedOperDatastore.getActorContext()));
+
+        } catch (final DOMDataTreeShardCreationFailedException e) {
+            throw new IllegalStateException(
+                        "Unable to create datastoreClient for oper DS prefix configuration shard.", e);
         }
+
+        writerMap.put(LogicalDatastoreType.CONFIGURATION, new PrefixedShardConfigWriter(
+                configurationShardMap.get(LogicalDatastoreType.CONFIGURATION).getKey()));
+
+        writerMap.put(LogicalDatastoreType.OPERATIONAL, new PrefixedShardConfigWriter(
+                configurationShardMap.get(LogicalDatastoreType.OPERATIONAL).getKey()));
+
+        updateHandler.initListener(distributedConfigDatastore, LogicalDatastoreType.CONFIGURATION);
+        updateHandler.initListener(distributedOperDatastore, LogicalDatastoreType.OPERATIONAL);
+
+        distributedConfigDatastore.getActorContext().getShardManager().tell(InitConfigListener.INSTANCE, noSender());
+        distributedOperDatastore.getActorContext().getShardManager().tell(InitConfigListener.INSTANCE, noSender());
+
+
+        //create shard registration for DEFAULT_SHARD
+        initDefaultShard(LogicalDatastoreType.CONFIGURATION);
+        initDefaultShard(LogicalDatastoreType.OPERATIONAL);
+    }
+
+    private ListenableFuture<List<Void>> handleConfigShardLookup() {
+
+        final ListenableFuture<Void> configFuture = lookupConfigShard(LogicalDatastoreType.CONFIGURATION);
+        final ListenableFuture<Void> operFuture = lookupConfigShard(LogicalDatastoreType.OPERATIONAL);
+
+        return Futures.allAsList(configFuture, operFuture);
+    }
+
+    private ListenableFuture<Void> lookupConfigShard(final LogicalDatastoreType type) {
+        final SettableFuture<Void> future = SettableFuture.create();
+
+        final Future<Object> ask =
+                Patterns.ask(shardedDataTreeActor, new StartConfigShardLookup(type), SHARD_FUTURE_TIMEOUT);
+
+        ask.onComplete(new OnComplete<Object>() {
+            @Override
+            public void onComplete(final Throwable throwable, final Object result) {
+                if (throwable != null) {
+                    future.setException(throwable);
+                } else {
+                    future.set(null);
+                }
+            }
+        }, actorSystem.dispatcher());
+
+        return future;
     }
 
     @Nonnull
@@ -135,96 +276,131 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
             final T listener, final Collection<DOMDataTreeIdentifier> subtrees,
             final boolean allowRxMerges, final Collection<DOMDataTreeProducer> producers)
             throws DOMDataTreeLoopException {
+        return shardedDOMDataTree.registerListener(listener, subtrees, allowRxMerges, producers);
+    }
 
-        throw new UnsupportedOperationException("Not implemented");
+    @Override
+    public ClassToInstanceMap<DOMDataTreeServiceExtension> getExtensions() {
+        return ImmutableClassToInstanceMap.of();
     }
 
     @Nonnull
     @Override
     public DOMDataTreeProducer createProducer(@Nonnull final Collection<DOMDataTreeIdentifier> subtrees) {
-        LOG.debug("{} - Creating producer for {}",
-                distributedConfigDatastore.getActorContext().getClusterWrapper().getCurrentMemberName(), subtrees);
+        LOG.debug("{} - Creating producer for {}", memberName, subtrees);
         final DOMDataTreeProducer producer = shardedDOMDataTree.createProducer(subtrees);
 
         final Object response = distributedConfigDatastore.getActorContext()
                 .executeOperation(shardedDataTreeActor, new ProducerCreated(subtrees));
         if (response == null) {
-            LOG.debug("{} - Received success from remote nodes, creating producer:{}",
-                    distributedConfigDatastore.getActorContext().getClusterWrapper().getCurrentMemberName(), subtrees);
+            LOG.debug("{} - Received success from remote nodes, creating producer:{}", memberName, subtrees);
             return new ProxyProducer(producer, subtrees, shardedDataTreeActor,
-                    distributedConfigDatastore.getActorContext());
-        } else if (response instanceof Exception) {
-            closeProducer(producer);
-            throw Throwables.propagate((Exception) response);
-        } else {
-            closeProducer(producer);
-            throw new RuntimeException("Unexpected response to create producer received." + response);
+                    distributedConfigDatastore.getActorContext(), shards);
+        }
+
+        closeProducer(producer);
+
+        if (response instanceof Throwable) {
+            Throwables.throwIfUnchecked((Throwable) response);
+            throw new RuntimeException((Throwable) response);
         }
+        throw new RuntimeException("Unexpected response to create producer received." + response);
     }
 
     @Override
-    @SuppressWarnings("checkstyle:IllegalCatch")
-    //TODO: it would be better to block here until the message is processed by the actor
-    public DistributedShardRegistration createDistributedShard(
+    public CompletionStage<DistributedShardRegistration> createDistributedShard(
             final DOMDataTreeIdentifier prefix, final Collection<MemberName> replicaMembers)
-            throws DOMDataTreeShardingConflictException, DOMDataTreeProducerException {
-        final DOMDataTreePrefixTableEntry<DOMDataTreeShardRegistration<DOMDataTreeShard>> lookup =
-                shards.lookup(prefix);
-        if (lookup != null && lookup.getValue().getPrefix().equals(prefix)) {
-            throw new DOMDataTreeShardingConflictException(
-                    "Prefix " + prefix + " is already occupied by another shard.");
+            throws DOMDataTreeShardingConflictException {
+
+        synchronized (shards) {
+            final DOMDataTreePrefixTableEntry<DOMDataTreeShardRegistration<DOMDataTreeShard>> lookup =
+                    shards.lookup(prefix);
+            if (lookup != null && lookup.getValue().getPrefix().equals(prefix)) {
+                throw new DOMDataTreeShardingConflictException(
+                        "Prefix " + prefix + " is already occupied by another shard.");
+            }
         }
 
-        PrefixShardConfiguration config = new PrefixShardConfiguration(prefix, "prefix", replicaMembers);
-        shardedDataTreeActor.tell(new CreatePrefixShard(config), noSender());
+        final PrefixedShardConfigWriter writer = writerMap.get(prefix.getDatastoreType());
+
+        final ListenableFuture<Void> writeFuture =
+                writer.writeConfig(prefix.getRootIdentifier(), replicaMembers);
+
+        final Promise<DistributedShardRegistration> shardRegistrationPromise = akka.dispatch.Futures.promise();
+        Futures.addCallback(writeFuture, new FutureCallback<Void>() {
+            @Override
+            public void onSuccess(@Nullable final Void result) {
+
+                final Future<Object> ask =
+                        Patterns.ask(shardedDataTreeActor, new LookupPrefixShard(prefix), SHARD_FUTURE_TIMEOUT);
+
+                shardRegistrationPromise.completeWith(ask.transform(
+                        new Mapper<Object, DistributedShardRegistration>() {
+                            @Override
+                            public DistributedShardRegistration apply(final Object parameter) {
+                                return new DistributedShardRegistrationImpl(
+                                        prefix, shardedDataTreeActor, DistributedShardedDOMDataTree.this);
+                            }
+                        },
+                        new Mapper<Throwable, Throwable>() {
+                            @Override
+                            public Throwable apply(final Throwable throwable) {
+                                return new DOMDataTreeShardCreationFailedException(
+                                        "Unable to create a cds shard.", throwable);
+                            }
+                        }, actorSystem.dispatcher()));
+            }
+
+            @Override
+            public void onFailure(final Throwable throwable) {
+                shardRegistrationPromise.failure(
+                        new DOMDataTreeShardCreationFailedException("Unable to create a cds shard.", throwable));
+            }
+        }, MoreExecutors.directExecutor());
 
-        return new DistributedShardRegistrationImpl(prefix, shardedDataTreeActor, this);
+        return FutureConverters.toJava(shardRegistrationPromise.future());
     }
 
     void resolveShardAdditions(final Set<DOMDataTreeIdentifier> additions) {
-        LOG.debug("Member {}: Resolving additions : {}", memberName, additions);
-        final ArrayList<DOMDataTreeIdentifier> list = new ArrayList<>(additions);
+        LOG.debug("{}: Resolving additions : {}", memberName, additions);
         // we need to register the shards from top to bottom, so we need to atleast make sure the ordering reflects that
-        Collections.sort(list, (o1, o2) -> {
-            if (o1.getRootIdentifier().getPathArguments().size() < o2.getRootIdentifier().getPathArguments().size()) {
-                return -1;
-            } else if (o1.getRootIdentifier().getPathArguments().size()
-                    == o2.getRootIdentifier().getPathArguments().size()) {
-                return 0;
-            } else {
-                return 1;
-            }
-        });
-        list.forEach(this::createShardFrontend);
+        additions
+            .stream()
+            .sorted(Comparator.comparingInt(o -> o.getRootIdentifier().getPathArguments().size()))
+            .forEachOrdered(this::createShardFrontend);
     }
 
     void resolveShardRemovals(final Set<DOMDataTreeIdentifier> removals) {
-        LOG.debug("Member {}: Resolving removals : {}", memberName, removals);
+        LOG.debug("{}: Resolving removals : {}", memberName, removals);
 
         // do we need to go from bottom to top?
         removals.forEach(this::despawnShardFrontend);
     }
 
     private void createShardFrontend(final DOMDataTreeIdentifier prefix) {
-        LOG.debug("Member {}: Creating CDS shard for prefix: {}", memberName, prefix);
+        LOG.debug("{}: Creating CDS shard for prefix: {}", memberName, prefix);
         final String shardName = ClusterUtils.getCleanShardName(prefix.getRootIdentifier());
-        final DistributedDataStore distributedDataStore =
+        final AbstractDataStore distributedDataStore =
                 prefix.getDatastoreType().equals(org.opendaylight.mdsal.common.api.LogicalDatastoreType.CONFIGURATION)
                         ? distributedConfigDatastore : distributedOperDatastore;
 
-        try (final DOMDataTreeProducer producer = localCreateProducer(Collections.singletonList(prefix))) {
+        try (DOMDataTreeProducer producer = localCreateProducer(Collections.singletonList(prefix))) {
             final Entry<DataStoreClient, ActorRef> entry =
                     createDatastoreClient(shardName, distributedDataStore.getActorContext());
 
             final DistributedShardFrontend shard =
                     new DistributedShardFrontend(distributedDataStore, entry.getKey(), prefix);
 
-            @SuppressWarnings("unchecked")
             final DOMDataTreeShardRegistration<DOMDataTreeShard> reg =
-                    (DOMDataTreeShardRegistration) shardedDOMDataTree.registerDataTreeShard(prefix, shard, producer);
-            shards.store(prefix, reg);
+                    shardedDOMDataTree.registerDataTreeShard(prefix, shard, producer);
+
+            synchronized (shards) {
+                shards.store(prefix, reg);
+            }
+
         } catch (final DOMDataTreeShardingConflictException e) {
-            LOG.error("Prefix {} is already occupied by another shard", prefix, e);
+            LOG.error("{}: Prefix {} is already occupied by another shard",
+                    distributedConfigDatastore.getActorContext().getClusterWrapper().getCurrentMemberName(), prefix, e);
         } catch (DOMDataTreeProducerException e) {
             LOG.error("Unable to close producer", e);
         } catch (DOMDataTreeShardCreationFailedException e) {
@@ -233,19 +409,45 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
     }
 
     private void despawnShardFrontend(final DOMDataTreeIdentifier prefix) {
-        LOG.debug("Member {}: Removing CDS shard for prefix: {}", memberName, prefix);
-        final DOMDataTreePrefixTableEntry<DOMDataTreeShardRegistration<DOMDataTreeShard>> lookup =
-                shards.lookup(prefix);
+        LOG.debug("{}: Removing CDS shard for prefix: {}", memberName, prefix);
+        final DOMDataTreePrefixTableEntry<DOMDataTreeShardRegistration<DOMDataTreeShard>> lookup;
+        synchronized (shards) {
+            lookup = shards.lookup(prefix);
+        }
 
         if (lookup == null || !lookup.getValue().getPrefix().equals(prefix)) {
-            LOG.debug("Member {}: Received despawn for non-existing CDS shard frontend, prefix: {}, ignoring..",
+            LOG.debug("{}: Received despawn for non-existing CDS shard frontend, prefix: {}, ignoring..",
                     memberName, prefix);
             return;
         }
 
         lookup.getValue().close();
         // need to remove from our local table thats used for tracking
-        shards.remove(prefix);
+        synchronized (shards) {
+            shards.remove(prefix);
+        }
+
+        final PrefixedShardConfigWriter writer = writerMap.get(prefix.getDatastoreType());
+        final ListenableFuture<Void> future = writer.removeConfig(prefix.getRootIdentifier());
+
+        Futures.addCallback(future, new FutureCallback<Void>() {
+            @Override
+            public void onSuccess(@Nullable final Void result) {
+                LOG.debug("{} - Succesfuly removed shard for {}", memberName, prefix);
+            }
+
+            @Override
+            public void onFailure(final Throwable throwable) {
+                LOG.error("Removal of shard {} from configuration failed.", prefix, throwable);
+            }
+        }, MoreExecutors.directExecutor());
+    }
+
+    DOMDataTreePrefixTableEntry<DOMDataTreeShardRegistration<DOMDataTreeShard>> lookupShardFrontend(
+            final DOMDataTreeIdentifier prefix) {
+        synchronized (shards) {
+            return shards.lookup(prefix);
+        }
     }
 
     DOMDataTreeProducer localCreateProducer(final Collection<DOMDataTreeIdentifier> prefix) {
@@ -262,6 +464,10 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
 
         LOG.debug("Registering shard[{}] at prefix: {}", shard, prefix);
 
+        if (producer instanceof ProxyProducer) {
+            return shardedDOMDataTree.registerDataTreeShard(prefix, shard, ((ProxyProducer) producer).delegate());
+        }
+
         return shardedDOMDataTree.registerDataTreeShard(prefix, shard, producer);
     }
 
@@ -270,7 +476,7 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
             final String shardName, final ActorContext actorContext)
             throws DOMDataTreeShardCreationFailedException {
 
-        LOG.debug("Creating distributed datastore client for shard {}", shardName);
+        LOG.debug("{}: Creating distributed datastore client for shard {}", memberName, shardName);
         final Props distributedDataStoreClientProps =
                 SimpleDataStoreClientActor.props(memberName, "Shard-" + shardName, actorContext, shardName);
 
@@ -279,22 +485,59 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
             return new SimpleEntry<>(SimpleDataStoreClientActor
                     .getDistributedDataStoreClient(clientActor, 30, TimeUnit.SECONDS), clientActor);
         } catch (final Exception e) {
-            LOG.error("Failed to get actor for {}", distributedDataStoreClientProps, e);
+            LOG.error("{}: Failed to get actor for {}", distributedDataStoreClientProps, memberName, e);
             clientActor.tell(PoisonPill.getInstance(), noSender());
             throw new DOMDataTreeShardCreationFailedException(
                     "Unable to create datastore client for shard{" + shardName + "}", e);
         }
     }
 
-    private DistributedShardRegistration initDefaultShard(final LogicalDatastoreType logicalDatastoreType)
-            throws DOMDataTreeProducerException, DOMDataTreeShardingConflictException {
-        final Collection<Member> members = JavaConverters.asJavaCollectionConverter(
-            Cluster.get(actorSystem).state().members()).asJavaCollection();
-        final Collection<MemberName> names = Collections2.transform(members,
-            m -> MemberName.forName(m.roles().iterator().next()));
+    @SuppressWarnings("checkstyle:IllegalCatch")
+    private void initDefaultShard(final LogicalDatastoreType logicalDatastoreType) {
 
-        return createDistributedShard(
-                new DOMDataTreeIdentifier(logicalDatastoreType, YangInstanceIdentifier.EMPTY), names);
+        final PrefixedShardConfigWriter writer = writerMap.get(logicalDatastoreType);
+
+        if (writer.checkDefaultIsPresent()) {
+            LOG.debug("{}: Default shard for {} is already present in the config. Possibly saved in snapshot.",
+                    memberName, logicalDatastoreType);
+        } else {
+            try {
+                // Currently the default shard configuration is present in the out-of-box modules.conf and is
+                // expected to be present. So look up the local default shard here and create the frontend.
+
+                // TODO we don't have to do it for config and operational default shard separately. Just one of them
+                // should be enough
+                final ActorContext actorContext = logicalDatastoreType == LogicalDatastoreType.CONFIGURATION
+                        ? distributedConfigDatastore.getActorContext() : distributedOperDatastore.getActorContext();
+
+                final Optional<ActorRef> defaultLocalShardOptional =
+                        actorContext.findLocalShard(ClusterUtils.getCleanShardName(YangInstanceIdentifier.EMPTY));
+
+                if (defaultLocalShardOptional.isPresent()) {
+                    LOG.debug("{}: Default shard for {} is already started, creating just frontend", memberName,
+                            logicalDatastoreType);
+                    createShardFrontend(new DOMDataTreeIdentifier(logicalDatastoreType, YangInstanceIdentifier.EMPTY));
+                }
+
+                // The local shard isn't present - we assume that means the local member isn't in the replica list
+                // and will be dynamically created later via an explicit add-shard-replica request. This is the
+                // bootstrapping mechanism to add a new node into an existing cluster. The following code to create
+                // the default shard as a prefix shard is problematic in this scenario so it is commented out. Since
+                // the default shard is a module-based shard by default, it makes sense to always treat it as such,
+                // ie bootstrap it in the same manner as the special prefix-configuration and EOS shards.
+//                final Collection<MemberName> names = distributedConfigDatastore.getActorContext().getConfiguration()
+//                        .getUniqueMemberNamesForAllShards();
+//                Await.result(FutureConverters.toScala(createDistributedShard(
+//                        new DOMDataTreeIdentifier(logicalDatastoreType, YangInstanceIdentifier.EMPTY), names)),
+//                        SHARD_FUTURE_TIMEOUT_DURATION);
+//            } catch (DOMDataTreeShardingConflictException e) {
+//                LOG.debug("{}: Default shard for {} already registered, possibly due to other node doing it faster",
+//                        memberName, logicalDatastoreType);
+            } catch (Exception e) {
+                LOG.error("{}: Default shard initialization for {} failed", memberName, logicalDatastoreType, e);
+                throw new RuntimeException(e);
+            }
+        }
     }
 
     private static void closeProducer(final DOMDataTreeProducer producer) {
@@ -326,7 +569,7 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
         throw new IllegalStateException("Failed to create actor for ShardedDOMDataTree", lastException);
     }
 
-    private static class DistributedShardRegistrationImpl implements DistributedShardRegistration {
+    private class DistributedShardRegistrationImpl implements DistributedShardRegistration {
 
         private final DOMDataTreeIdentifier prefix;
         private final ActorRef shardedDataTreeActor;
@@ -341,29 +584,57 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
         }
 
         @Override
-        public void close() {
+        public CompletionStage<Void> close() {
             // first despawn on the local node
             distributedShardedDOMDataTree.despawnShardFrontend(prefix);
             // update the config so the remote nodes are updated
-            shardedDataTreeActor.tell(new RemovePrefixShard(prefix), noSender());
+            final Future<Object> ask =
+                    Patterns.ask(shardedDataTreeActor, new PrefixShardRemovalLookup(prefix), SHARD_FUTURE_TIMEOUT);
+
+            final Future<Void> closeFuture = ask.transform(
+                    new Mapper<Object, Void>() {
+                        @Override
+                        public Void apply(final Object parameter) {
+                            return null;
+                        }
+                    },
+                    new Mapper<Throwable, Throwable>() {
+                        @Override
+                        public Throwable apply(final Throwable throwable) {
+                            return throwable;
+                        }
+                    }, actorSystem.dispatcher());
+
+            return FutureConverters.toJava(closeFuture);
         }
     }
 
-    private static final class ProxyProducer extends ForwardingObject implements DOMDataTreeProducer {
+    // TODO what about producers created by this producer?
+    // They should also be CDSProducers
+    private static final class ProxyProducer extends ForwardingObject implements CDSDataTreeProducer {
 
         private final DOMDataTreeProducer delegate;
         private final Collection<DOMDataTreeIdentifier> subtrees;
         private final ActorRef shardDataTreeActor;
         private final ActorContext actorContext;
+        @GuardedBy("shardAccessMap")
+        private final Map<DOMDataTreeIdentifier, CDSShardAccessImpl> shardAccessMap = new HashMap<>();
+
+        // We don't have to guard access to shardTable in ProxyProducer.
+        // ShardTable's entries relevant to this ProxyProducer shouldn't
+        // change during producer's lifetime.
+        private final DOMDataTreePrefixTable<DOMDataTreeShardRegistration<DOMDataTreeShard>> shardTable;
 
         ProxyProducer(final DOMDataTreeProducer delegate,
                       final Collection<DOMDataTreeIdentifier> subtrees,
                       final ActorRef shardDataTreeActor,
-                      final ActorContext actorContext) {
+                      final ActorContext actorContext,
+                      final DOMDataTreePrefixTable<DOMDataTreeShardRegistration<DOMDataTreeShard>> shardLayout) {
             this.delegate = Preconditions.checkNotNull(delegate);
             this.subtrees = Preconditions.checkNotNull(subtrees);
             this.shardDataTreeActor = Preconditions.checkNotNull(shardDataTreeActor);
             this.actorContext = Preconditions.checkNotNull(actorContext);
+            this.shardTable = Preconditions.checkNotNull(shardLayout);
         }
 
         @Nonnull
@@ -374,6 +645,7 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
 
         @Nonnull
         @Override
+        @SuppressWarnings("checkstyle:hiddenField")
         public DOMDataTreeProducer createProducer(@Nonnull final Collection<DOMDataTreeIdentifier> subtrees) {
             // TODO we probably don't need to distribute this on the remote nodes since once we have this producer
             // open we surely have the rights to all the subtrees.
@@ -381,12 +653,17 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
         }
 
         @Override
+        @SuppressWarnings("checkstyle:IllegalCatch")
         public void close() throws DOMDataTreeProducerException {
             delegate.close();
 
+            synchronized (shardAccessMap) {
+                shardAccessMap.values().forEach(CDSShardAccessImpl::close);
+            }
+
             final Object o = actorContext.executeOperation(shardDataTreeActor, new ProducerRemoved(subtrees));
             if (o instanceof DOMDataTreeProducerException) {
-                throw ((DOMDataTreeProducerException) o);
+                throw (DOMDataTreeProducerException) o;
             } else if (o instanceof Throwable) {
                 throw new DOMDataTreeProducerException("Unable to close producer", (Throwable) o);
             }
@@ -396,5 +673,33 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
         protected DOMDataTreeProducer delegate() {
             return delegate;
         }
+
+        @Nonnull
+        @Override
+        public CDSShardAccess getShardAccess(@Nonnull final DOMDataTreeIdentifier subtree) {
+            Preconditions.checkArgument(
+                    subtrees.stream().anyMatch(dataTreeIdentifier -> dataTreeIdentifier.contains(subtree)),
+                    "Subtree %s is not controlled by this producer %s", subtree, this);
+
+            final DOMDataTreePrefixTableEntry<DOMDataTreeShardRegistration<DOMDataTreeShard>> lookup =
+                    shardTable.lookup(subtree);
+            Preconditions.checkState(lookup != null, "Subtree %s is not contained in any registered shard.", subtree);
+
+            final DOMDataTreeIdentifier lookupId = lookup.getValue().getPrefix();
+
+            synchronized (shardAccessMap) {
+                if (shardAccessMap.get(lookupId) != null) {
+                    return shardAccessMap.get(lookupId);
+                }
+
+                // TODO Maybe we can have static factory method and return the same instance
+                // for same subtrees. But maybe it is not needed since there can be only one
+                // producer attached to some subtree at a time. And also how we can close ShardAccess
+                // then
+                final CDSShardAccessImpl shardAccess = new CDSShardAccessImpl(lookupId, actorContext);
+                shardAccessMap.put(lookupId, shardAccess);
+                return shardAccess;
+            }
+        }
     }
 }