Add getClusterDescription method to com.mongodb.client.MongoClient

JAVA-3307

Author: jyemin

driver-sync/src/main/com/mongodb/client/MongoClient.java

@@ -19,6 +19,9 @@
 import com.mongodb.ClientSessionOptions;
 import com.mongodb.MongoNamespace;
 import com.mongodb.annotations.Immutable;
+import com.mongodb.connection.ClusterDescription;
+import com.mongodb.connection.ClusterSettings;
+import com.mongodb.event.ClusterListener;
 import org.bson.Document;
 import org.bson.conversions.Bson;
 
@@ -230,4 +233,20 @@ public interface MongoClient extends Closeable {
      */
     <TResult> ChangeStreamIterable<TResult> watch(ClientSession clientSession, List<? extends Bson> pipeline, Class<TResult> resultClass);
 
+    /**
+     * Gets the current cluster description.
+     *
+     * <p>
+     * This method will not block, meaning that it may return a {@link ClusterDescription} whose {@code clusterType} is unknown
+     * and whose {@link com.mongodb.connection.ServerDescription}s are all in the connecting state.  If the application requires
+     * notifications after the driver has connected to a member of the cluster, it should register a {@link ClusterListener} via
+     * the {@link ClusterSettings} in {@link com.mongodb.MongoClientSettings}.
+     * </p>
+     *
+     * @return the current cluster description
+     * @see ClusterSettings.Builder#addClusterListener(ClusterListener)
+     * @see com.mongodb.MongoClientSettings.Builder#applyToClusterSettings(com.mongodb.Block)
+     * @since 3.11
+     */
+    ClusterDescription getClusterDescription();
 }

driver-sync/src/main/com/mongodb/client/internal/MongoClientImpl.java

@@ -33,6 +33,7 @@
 import com.mongodb.client.MongoIterable;
 import com.mongodb.client.model.changestream.ChangeStreamLevel;
 import com.mongodb.connection.Cluster;
+import com.mongodb.connection.ClusterDescription;
 import com.mongodb.connection.DefaultClusterFactory;
 import com.mongodb.connection.SocketSettings;
 import com.mongodb.connection.SocketStreamFactory;
@@ -175,6 +176,11 @@ public <TResult> ChangeStreamIterable<TResult> watch(final ClientSession clientS
         return createChangeStreamIterable(clientSession, pipeline, resultClass);
     }
 
+    @Override
+    public ClusterDescription getClusterDescription() {
+        return delegate.getCluster().getCurrentDescription();
+    }
+
     private <TResult> ChangeStreamIterable<TResult> createChangeStreamIterable(@Nullable final ClientSession clientSession,
                                                                                final List<? extends Bson> pipeline,
                                                                                final Class<TResult> resultClass) {

driver-sync/src/test/unit/com/mongodb/client/MongoClientSpecification.groovy

@@ -19,14 +19,21 @@ package com.mongodb.client
 import com.mongodb.MongoClientSettings
 import com.mongodb.MongoNamespace
 import com.mongodb.ReadConcern
+import com.mongodb.ServerAddress
 import com.mongodb.WriteConcern
-import com.mongodb.client.internal.ListDatabasesIterableImpl
 import com.mongodb.client.internal.MongoClientImpl
 import com.mongodb.client.internal.MongoDatabaseImpl
 import com.mongodb.client.internal.MongoIterables
 import com.mongodb.client.internal.TestOperationExecutor
 import com.mongodb.client.model.changestream.ChangeStreamLevel
 import com.mongodb.connection.Cluster
+import com.mongodb.connection.ClusterConnectionMode
+import com.mongodb.connection.ClusterDescription
+import com.mongodb.connection.ClusterType
+import com.mongodb.connection.ServerConnectionState
+import com.mongodb.connection.ServerDescription
+import com.mongodb.connection.ServerType
+import com.mongodb.connection.ServerVersion
 import org.bson.BsonDocument
 import org.bson.Document
 import spock.lang.Specification
@@ -154,4 +161,25 @@ class MongoClientSpecification extends Specification {
         then:
         thrown(IllegalArgumentException)
     }
+
+    def 'should get the cluster description'() {
+        given:
+        def clusterDescription = new ClusterDescription(ClusterConnectionMode.SINGLE, ClusterType.STANDALONE,
+                [ServerDescription.builder()
+                         .address(new ServerAddress())
+                         .type(ServerType.UNKNOWN)
+                         .state(ServerConnectionState.CONNECTING)
+                         .version(new ServerVersion())
+                         .build()])
+        def cluster = Mock(Cluster) {
+            1 * getCurrentDescription() >> {
+                clusterDescription
+            }
+        }
+        def settings = MongoClientSettings.builder().build()
+        def client = new MongoClientImpl(cluster, settings, new TestOperationExecutor([]))
+
+        expect:
+        client.getClusterDescription() == clusterDescription
+    }
 }