optimize javadoc

Author: hfutatzhanghb

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/fairness/RouterAsyncRpcFairnessPolicyController.java

@@ -30,6 +30,9 @@
 import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.
     DFS_ROUTER_ASYNC_RPC_MAX_ASYNC_CALL_PERMIT_DEFAULT;
 
+/**
+ * When router async rpc enabled, it is recommended to use this fairness controller.
+ */
 public class RouterAsyncRpcFairnessPolicyController extends
     AbstractRouterRpcFairnessPolicyController {
 

hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/async/TestRouterAsyncRpc.java

@@ -45,16 +45,17 @@ public class TestRouterAsyncRpc extends TestRouterRpc {
 
   @BeforeClass
   public static void globalSetUp() throws Exception {
-    // Start routers with only an RPC service
+    // Start routers with only an RPC service.
     Configuration routerConf = new RouterConfigBuilder()
         .metrics()
         .rpc()
         .build();
-    // We decrease the DN cache times to make the test faster
+    // We decrease the DN cache times to make the test faster.
     routerConf.setTimeDuration(
         RBFConfigKeys.DN_REPORT_CACHE_EXPIRE, 1, TimeUnit.SECONDS);
-    // use async router.
+    // Use async router.
     routerConf.setBoolean(DFS_ROUTER_ASYNC_RPC_ENABLE_KEY, true);
+    // Use RouterAsyncRpcFairnessPolicyController as the fairness controller.
     routerConf.setClass(DFS_ROUTER_FAIRNESS_POLICY_CONTROLLER_CLASS,
         RouterAsyncRpcFairnessPolicyController.class,
         RouterRpcFairnessPolicyController.class);
@@ -65,7 +66,7 @@ public static void globalSetUp() throws Exception {
   public void testSetup() throws Exception {
     super.testSetup();
     cluster = super.getCluster();
-    // Random router for this test
+    // Random router for this test.
     rndRouter = cluster.getRandomRouter();
   }