Remove unneeded cast
[controller.git] / opendaylight / md-sal / sal-distributed-datastore / src / main / java / org / opendaylight / controller / cluster / sharding / DistributedShardedDOMDataTree.java
index 69dfe4c7b7335186edd00aaf5384e9e45d6c2354..99c03768ed111bff08a9a8d9fbd8bcbd98e739d6 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,
@@ -14,40 +14,57 @@ 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.ForwardingObject;
+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.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.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;
@@ -63,13 +80,15 @@ 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.Await;
 import scala.concurrent.Future;
+import scala.concurrent.Promise;
 import scala.concurrent.duration.FiniteDuration;
 
 /**
@@ -84,30 +103,39 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
     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;
-    static final FiniteDuration SHARD_FUTURE_TIMEOUT_DURATION = new FiniteDuration(
-                    ShardedDataTreeActor.LOOKUP_TASK_MAX_RETRIES * ShardedDataTreeActor.LOOKUP_TASK_MAX_RETRIES * 3,
-                    TimeUnit.SECONDS);
+    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 =
             new EnumMap<>(LogicalDatastoreType.class);
 
+    private final EnumMap<LogicalDatastoreType, Entry<DataStoreClient, ActorRef>> configurationShardMap =
+            new EnumMap<>(LogicalDatastoreType.class);
+
+    private final EnumMap<LogicalDatastoreType, PrefixedShardConfigWriter> writerMap =
+            new EnumMap<>(LogicalDatastoreType.class);
+
+    private final PrefixedShardConfigUpdateHandler updateHandler;
+
     public DistributedShardedDOMDataTree(final ActorSystemProvider actorSystemProvider,
-                                         final DistributedDataStore distributedOperDatastore,
-                                         final DistributedDataStore distributedConfigDatastore) {
+                                         final AbstractDataStore distributedOperDatastore,
+                                         final AbstractDataStore distributedConfigDatastore) {
         this.actorSystem = Preconditions.checkNotNull(actorSystemProvider).getActorSystem();
         this.distributedOperDatastore = Preconditions.checkNotNull(distributedOperDatastore);
         this.distributedConfigDatastore = Preconditions.checkNotNull(distributedConfigDatastore);
@@ -119,27 +147,144 @@ 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();
 
+        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 {
+            LOG.debug("{} - starting config shard lookup.",
+                    distributedConfigDatastore.getActorContext().getCurrentMemberName());
+
+            // 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());
+
+            LOG.debug("Prefix configuration shards ready - creating clients");
+
+        } catch (InterruptedException | ExecutionException | TimeoutException e) {
+            throw new IllegalStateException("Prefix config shards not found", e);
+        }
+
+        try {
+            LOG.debug("Prefix configuration shards ready - creating clients");
+            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
         try {
             defaultShardRegistrations.put(LogicalDatastoreType.CONFIGURATION,
                     initDefaultShard(LogicalDatastoreType.CONFIGURATION));
         } catch (final InterruptedException | ExecutionException e) {
-            LOG.error("Unable to create default shard frontend for config shard", e);
+            throw new IllegalStateException("Unable to create default shard frontend for config shard", e);
         }
 
         try {
             defaultShardRegistrations.put(LogicalDatastoreType.OPERATIONAL,
                     initDefaultShard(LogicalDatastoreType.OPERATIONAL));
         } catch (final InterruptedException | ExecutionException e) {
-            LOG.error("Unable to create default shard frontend for operational shard", e);
+            throw new IllegalStateException("Unable to create default shard frontend for operational shard", e);
         }
     }
 
+    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) throws Throwable {
+                if (throwable != null) {
+                    future.setException(throwable);
+                } else {
+                    future.set(null);
+                }
+            }
+        }, actorSystem.dispatcher());
+
+        return future;
+    }
+
     @Nonnull
     @Override
     public <T extends DOMDataTreeListener> ListenerRegistration<T> registerListener(
@@ -162,7 +307,7 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
             LOG.debug("{} - Received success from remote nodes, creating producer:{}",
                     distributedConfigDatastore.getActorContext().getClusterWrapper().getCurrentMemberName(), subtrees);
             return new ProxyProducer(producer, subtrees, shardedDataTreeActor,
-                    distributedConfigDatastore.getActorContext());
+                    distributedConfigDatastore.getActorContext(), shards);
         } else if (response instanceof Exception) {
             closeProducer(producer);
             throw Throwables.propagate((Exception) response);
@@ -176,34 +321,54 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
     public CompletionStage<DistributedShardRegistration> createDistributedShard(
             final DOMDataTreeIdentifier prefix, final Collection<MemberName> replicaMembers)
             throws DOMDataTreeShardingConflictException {
-        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.");
+
+        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.");
+            }
         }
 
-        final PrefixShardConfiguration config = new PrefixShardConfiguration(prefix, "prefix", replicaMembers);
+        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()));
+            }
 
-        final Future<Object> ask =
-                Patterns.ask(shardedDataTreeActor, new CreatePrefixShard(config), SHARD_FUTURE_TIMEOUT);
-
-        final Future<DistributedShardRegistration> shardRegistrationFuture = 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());
-
-        return FutureConverters.toJava(shardRegistrationFuture);
+            @Override
+            public void onFailure(final Throwable throwable) {
+                shardRegistrationPromise.failure(
+                        new DOMDataTreeShardCreationFailedException("Unable to create a cds shard.", throwable));
+            }
+        });
+
+        return FutureConverters.toJava(shardRegistrationPromise.future());
     }
 
     void resolveShardAdditions(final Set<DOMDataTreeIdentifier> additions) {
@@ -233,23 +398,27 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
     private void createShardFrontend(final DOMDataTreeIdentifier prefix) {
         LOG.debug("Member {}: 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) {
@@ -259,8 +428,10 @@ 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);
+        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..",
@@ -270,13 +441,31 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
 
         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);
+            }
+        });
     }
 
     DOMDataTreePrefixTableEntry<DOMDataTreeShardRegistration<DOMDataTreeShard>> lookupShardFrontend(
             final DOMDataTreeIdentifier prefix) {
-        return shards.lookup(prefix);
-
+        synchronized (shards) {
+            return shards.lookup(prefix);
+        }
     }
 
     DOMDataTreeProducer localCreateProducer(final Collection<DOMDataTreeIdentifier> prefix) {
@@ -321,23 +510,54 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
         }
     }
 
+    @SuppressWarnings("checkstyle:IllegalCatch")
     private DistributedShardRegistration initDefaultShard(final LogicalDatastoreType logicalDatastoreType)
             throws ExecutionException, InterruptedException {
-        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()));
+        final Collection<MemberName> names =
+                distributedConfigDatastore.getActorContext().getConfiguration().getUniqueMemberNamesForAllShards();
 
-        try {
-            // we should probably only have one node create the default shards
-            return createDistributedShard(
-                    new DOMDataTreeIdentifier(logicalDatastoreType, YangInstanceIdentifier.EMPTY), names)
-                    .toCompletableFuture().get();
-        } catch (DOMDataTreeShardingConflictException e) {
-            LOG.debug("Default shard already registered, possibly due to other node doing it faster");
+        final PrefixedShardConfigWriter writer = writerMap.get(logicalDatastoreType);
+
+        if (writer.checkDefaultIsPresent()) {
+            LOG.debug("Default shard for {} is already present in the config. Possibly saved in snapshot.",
+                    logicalDatastoreType);
             return new DistributedShardRegistrationImpl(
                     new DOMDataTreeIdentifier(logicalDatastoreType, YangInstanceIdentifier.EMPTY),
                     shardedDataTreeActor, this);
+        } else {
+            try {
+                // There can be situation when there is already started default shard
+                // because it is present in modules.conf. In that case we have to create
+                // just frontend for default shard, but not shard itself
+                // 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 is already started, creating just frontend", logicalDatastoreType);
+                    createShardFrontend(new DOMDataTreeIdentifier(logicalDatastoreType, YangInstanceIdentifier.EMPTY));
+                    return new DistributedShardRegistrationImpl(
+                            new DOMDataTreeIdentifier(logicalDatastoreType, YangInstanceIdentifier.EMPTY),
+                            shardedDataTreeActor, this);
+                }
+
+                // we should probably only have one node create the default shards
+                return Await.result(FutureConverters.toScala(createDistributedShard(
+                        new DOMDataTreeIdentifier(logicalDatastoreType, YangInstanceIdentifier.EMPTY), names)),
+                        SHARD_FUTURE_TIMEOUT_DURATION);
+            } catch (DOMDataTreeShardingConflictException e) {
+                LOG.debug("Default shard already registered, possibly due to other node doing it faster");
+                return new DistributedShardRegistrationImpl(
+                        new DOMDataTreeIdentifier(logicalDatastoreType, YangInstanceIdentifier.EMPTY),
+                        shardedDataTreeActor, this);
+            } catch (Exception e) {
+                LOG.error("{} default shard initialization failed", logicalDatastoreType, e);
+                throw new RuntimeException(e);
+            }
         }
     }
 
@@ -390,18 +610,18 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
             distributedShardedDOMDataTree.despawnShardFrontend(prefix);
             // update the config so the remote nodes are updated
             final Future<Object> ask =
-                    Patterns.ask(shardedDataTreeActor, new RemovePrefixShard(prefix), SHARD_FUTURE_TIMEOUT);
+                    Patterns.ask(shardedDataTreeActor, new PrefixShardRemovalLookup(prefix), SHARD_FUTURE_TIMEOUT);
 
             final Future<Void> closeFuture = ask.transform(
                     new Mapper<Object, Void>() {
                         @Override
-                        public Void apply(Object parameter) {
+                        public Void apply(final Object parameter) {
                             return null;
                         }
                     },
                     new Mapper<Throwable, Throwable>() {
                         @Override
-                        public Throwable apply(Throwable throwable) {
+                        public Throwable apply(final Throwable throwable) {
                             return throwable;
                         }
                     }, actorSystem.dispatcher());
@@ -410,21 +630,32 @@ public class DistributedShardedDOMDataTree implements DOMDataTreeService, DOMDat
         }
     }
 
-    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
@@ -442,12 +673,17 @@ 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);
             }
@@ -457,5 +693,33 @@ 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 {} is not controlled by this producer {}", subtree, this);
+
+            final DOMDataTreePrefixTableEntry<DOMDataTreeShardRegistration<DOMDataTreeShard>> lookup =
+                    shardTable.lookup(subtree);
+            Preconditions.checkState(lookup != null, "Subtree {} is not contained in any registered shard.");
+
+            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;
+            }
+        }
     }
 }