HDFS-13634. RBF: Configurable value in xml for async connection request queue size. Contributed by CR Hota.

(cherry picked from commit a0ebb6b39f2932d3ea2fb5e287f52b841e108428)

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/ConnectionManager.java

@@ -49,9 +49,6 @@ public class ConnectionManager {
   private static final Logger LOG =
       LoggerFactory.getLogger(ConnectionManager.class);
 
-  /** Number of parallel new connections to create. */
-  protected static final int MAX_NEW_CONNECTIONS = 100;
-
   /** Minimum amount of active connections: 50%. */
   protected static final float MIN_ACTIVE_RATIO = 0.5f;
 
@@ -77,8 +74,10 @@ public class ConnectionManager {
   private final Lock writeLock = readWriteLock.writeLock();
 
   /** Queue for creating new connections. */
-  private final BlockingQueue<ConnectionPool> creatorQueue =
-      new ArrayBlockingQueue<>(MAX_NEW_CONNECTIONS);
+  private final BlockingQueue<ConnectionPool> creatorQueue;
+  /** Max size of queue for creating new connections. */
+  private final int creatorQueueMaxSize;
+
   /** Create new connections asynchronously. */
   private final ConnectionCreator creator;
   /** Periodic executor to remove stale connection pools. */
@@ -106,7 +105,12 @@ public class ConnectionManager {
     this.pools = new HashMap<>();
 
     // Create connections in a thread asynchronously
-    this.creator = new ConnectionCreator(creatorQueue);
+    this.creatorQueueMaxSize = this.conf.getInt(
+        RBFConfigKeys.DFS_ROUTER_NAMENODE_CONNECTION_CREATOR_QUEUE_SIZE,
+        RBFConfigKeys.DFS_ROUTER_NAMENODE_CONNECTION_CREATOR_QUEUE_SIZE_DEFAULT
+        );
+    this.creatorQueue = new ArrayBlockingQueue<>(this.creatorQueueMaxSize);
+    this.creator = new ConnectionCreator(this.creatorQueue);
     this.creator.setDaemon(true);
 
     // Cleanup periods
@@ -213,7 +217,7 @@ public class ConnectionManager {
     if (conn == null || !conn.isUsable()) {
       if (!this.creatorQueue.offer(pool)) {
         LOG.error("Cannot add more than {} connections at the same time",
-            MAX_NEW_CONNECTIONS);
+            this.creatorQueueMaxSize);
       }
     }
 

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RBFConfigKeys.java

@@ -93,6 +93,11 @@ public class RBFConfigKeys extends CommonConfigurationKeysPublic {
       TimeUnit.SECONDS.toMillis(5);
 
   // HDFS Router NN client
+  public static final String
+      DFS_ROUTER_NAMENODE_CONNECTION_CREATOR_QUEUE_SIZE =
+      FEDERATION_ROUTER_PREFIX + "connection.creator.queue-size";
+  public static final int
+      DFS_ROUTER_NAMENODE_CONNECTION_CREATOR_QUEUE_SIZE_DEFAULT = 100;
   public static final String DFS_ROUTER_NAMENODE_CONNECTION_POOL_SIZE =
       FEDERATION_ROUTER_PREFIX + "connection.pool-size";
   public static final int DFS_ROUTER_NAMENODE_CONNECTION_POOL_SIZE_DEFAULT =

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/resources/hdfs-rbf-default.xml

@@ -93,6 +93,14 @@
     </description>
   </property>
 
+  <property>
+    <name>dfs.federation.router.connection.creator.queue-size</name>
+    <value>100</value>
+    <description>
+      Size of async connection creator queue.
+    </description>
+  </property>
+
   <property>
     <name>dfs.federation.router.connection.pool-size</name>
     <value>1</value>