[GitHub] [hadoop] kokonguyen191 commented on a diff in pull request #4199: HDFS-14750. RBF: Support dynamic handler allocation in routers

[GitBox <gi...@apache.org>]

kokonguyen191 commented on code in PR #4199:
URL: https://github.com/apache/hadoop/pull/4199#discussion_r866709948


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hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/fairness/TestDynamicRouterRpcFairnessPolicyController.java:
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@@ -0,0 +1,177 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hdfs.server.federation.fairness;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.atomic.LongAdder;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hdfs.HdfsConfiguration;
+import org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys;
+
+import static org.apache.hadoop.hdfs.server.federation.fairness.RouterRpcFairnessConstants.CONCURRENT_NS;
+import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.DFS_ROUTER_HANDLER_COUNT_KEY;
+import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.DFS_ROUTER_MONITOR_NAMENODE;
+
+/**
+ * Test functionality of {@link DynamicRouterRpcFairnessPolicyController).
+ */
+public class TestDynamicRouterRpcFairnessPolicyController {
+
+  private static String nameServices = "ns1.nn1, ns1.nn2, ns2.nn1, ns2.nn2";
+
+  @Test
+  public void testDynamicControllerSimple() throws InterruptedException {
+    verifyDynamicControllerSimple(true);
+    verifyDynamicControllerSimple(false);
+  }
+
+  @Test
+  public void testDynamicControllerAllPermitsAcquired() throws InterruptedException {
+    verifyDynamicControllerAllPermitsAcquired(true);
+    verifyDynamicControllerAllPermitsAcquired(false);
+  }
+
+  private void verifyDynamicControllerSimple(boolean manualRefresh)
+      throws InterruptedException {
+    // 3 permits each ns
+    DynamicRouterRpcFairnessPolicyController controller;
+    if (manualRefresh) {
+      controller = getFairnessPolicyController(9);
+    } else {
+      controller = getFairnessPolicyController(9, 4000);
+    }
+    for (int i = 0; i < 3; i++) {
+      Assert.assertTrue(controller.acquirePermit("ns1"));
+      Assert.assertTrue(controller.acquirePermit("ns2"));
+      Assert.assertTrue(controller.acquirePermit(CONCURRENT_NS));
+    }
+    Assert.assertFalse(controller.acquirePermit("ns1"));
+    Assert.assertFalse(controller.acquirePermit("ns2"));
+    Assert.assertFalse(controller.acquirePermit(CONCURRENT_NS));
+
+    // Release all permits
+    for (int i = 0; i < 3; i++) {
+      controller.releasePermit("ns1");
+      controller.releasePermit("ns2");
+      controller.releasePermit(CONCURRENT_NS);
+    }
+
+    // Inject dummy metrics
+    // Split half half for ns1 and concurrent
+    Map<String, LongAdder> rejectedPermitsPerNs = new HashMap<>();
+    Map<String, LongAdder> acceptedPermitsPerNs = new HashMap<>();
+    injectDummyMetrics(rejectedPermitsPerNs, "ns1", 10);
+    injectDummyMetrics(rejectedPermitsPerNs, "ns2", 0);
+    injectDummyMetrics(rejectedPermitsPerNs, CONCURRENT_NS, 10);
+    controller.setMetrics(rejectedPermitsPerNs, acceptedPermitsPerNs);
+
+    if (manualRefresh) {
+      controller.refreshPermitsCap();
+    } else {
+      Thread.sleep(5000);
+    }
+
+    // Current permits count should be 5:1:5

Review Comment:
   Yes it's an inherent issue with the approach when permit count scales with traffic.
   
   For example, initial handlers assigned to ns0,ns1,concurrent are 5,5,30 (40 total). After a while, all 3 namespaces have the same traffic and 40 handlers have to be spread between all of them, leading to a tiebreaking situation. Not sure what approach is best to handle these kinds of situations.



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