HADOOP-13932. Fix indefinite article in comments (Contributed by LiXin Ge via Daniel Templeton)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImagePreTransactionalStorageInspector.java

@@ -41,7 +41,7 @@ import org.apache.hadoop.hdfs.server.namenode.NNStorage.NameNodeFile;
 import org.apache.hadoop.io.IOUtils;
 
 /**
- * Inspects a FSImage storage directory in the "old" (pre-HDFS-1073) format.
+ * Inspects an FSImage storage directory in the "old" (pre-HDFS-1073) format.
  * This format has the following data files:
  *   - fsimage
  *   - fsimage.ckpt (when checkpoint is being uploaded)

hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HdfsRollingUpgrade.md

@@ -67,7 +67,7 @@ Note that rolling upgrade is supported only from Hadoop-2.4.0 onwards.
 
 ### Upgrade without Downtime
 
-In a HA cluster, there are two or more *NameNodes (NNs)*, many *DataNodes (DNs)*,
+In an HA cluster, there are two or more *NameNodes (NNs)*, many *DataNodes (DNs)*,
 a few *JournalNodes (JNs)* and a few *ZooKeeperNodes (ZKNs)*.
 *JNs* is relatively stable and does not require upgrade when upgrading HDFS in most of the cases.
 In the rolling upgrade procedure described here,
@@ -78,7 +78,7 @@ Upgrading *JNs* and *ZKNs* may incur cluster downtime.
 
 Suppose there are two namenodes *NN1* and *NN2*,
 where *NN1* and *NN2* are respectively in active and standby states.
-The following are the steps for upgrading a HA cluster:
+The following are the steps for upgrading an HA cluster:
 
 1. Prepare Rolling Upgrade
     1. Run "[`hdfs dfsadmin -rollingUpgrade prepare`](#dfsadmin_-rollingUpgrade)"
@@ -135,7 +135,7 @@ However, datanodes can still be upgraded in a rolling manner.
 
 In a non-HA cluster, there are a *NameNode (NN)*, a *SecondaryNameNode (SNN)*
 and many *DataNodes (DNs)*.
-The procedure for upgrading a non-HA cluster is similar to upgrading a HA cluster
+The procedure for upgrading a non-HA cluster is similar to upgrading an HA cluster
 except that Step 2 "Upgrade Active and Standby *NNs*" is changed to below:
 
 * Upgrade *NN* and *SNN*
@@ -180,7 +180,7 @@ are not changed between these two releases.
 
 ### Downgrade without Downtime
 
-In a HA cluster,
+In an HA cluster,
 when a rolling upgrade from an old software release to a new software release is in progress,
 it is possible to downgrade, in a rolling fashion, the upgraded machines back to the old software release.
 Same as before, suppose *NN1* and *NN2* are respectively in active and standby states.

hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/LibHdfs.md

@@ -76,7 +76,7 @@ libdhfs is thread safe.
 
 *   Concurrency and Hadoop FS "handles"
 
-    The Hadoop FS implementation includes a FS handle cache which
+    The Hadoop FS implementation includes an FS handle cache which
     caches based on the URI of the namenode along with the user
     connecting. So, all calls to `hdfsConnect` will return the same
     handle but calls to `hdfsConnectAsUser` with different users will

hadoop-yarn-project/hadoop-yarn/dev-support/jdiff/Apache_Hadoop_YARN_API_2.6.0.xml

@@ -9801,7 +9801,7 @@
       <param name="defaultPort" type="int"/>
       <doc>
       <![CDATA[Get the socket address for <code>name</code> property as a
- <code>InetSocketAddress</code>. On a HA cluster,
+ <code>InetSocketAddress</code>. On an HA cluster,
  this fetches the address corresponding to the RM identified by
  {@link #RM_HA_ID}.
  @param name property name.

hadoop-yarn-project/hadoop-yarn/dev-support/jdiff/Apache_Hadoop_YARN_API_2.7.2.xml

@@ -9416,7 +9416,7 @@
       <param name="defaultPort" type="int"/>
       <doc>
       <![CDATA[Get the socket address for <code>name</code> property as a
- <code>InetSocketAddress</code>. On a HA cluster,
+ <code>InetSocketAddress</code>. On an HA cluster,
  this fetches the address corresponding to the RM identified by
  {@link #RM_HA_ID}.
  @param name property name.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/conf/HAUtil.java

@@ -208,7 +208,7 @@ public class HAUtil {
 
   @VisibleForTesting
   static String getNeedToSetValueMessage(String confKey) {
-    return confKey + " needs to be set in a HA configuration.";
+    return confKey + " needs to be set in an HA configuration.";
   }
 
   @VisibleForTesting
@@ -223,7 +223,7 @@ public class HAUtil {
                                                         String rmId) {
     return YarnConfiguration.RM_HA_IDS + "("
       + ids +  ") need to contain " + YarnConfiguration.RM_HA_ID + "("
-      + rmId + ") in a HA configuration.";
+      + rmId + ") in an HA configuration.";
   }
 
   @VisibleForTesting

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/conf/YarnConfiguration.java

@@ -2702,7 +2702,7 @@ public class YarnConfiguration extends Configuration {
 
   /**
    * Get the socket address for <code>name</code> property as a
-   * <code>InetSocketAddress</code>. On a HA cluster,
+   * <code>InetSocketAddress</code>. On an HA cluster,
    * this fetches the address corresponding to the RM identified by
    * {@link #RM_HA_ID}.
    * @param name property name.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/resources/yarn-default.xml

@@ -427,7 +427,7 @@
   <property>
     <description>Host:Port of the ZooKeeper server to be used by the RM. This
       must be supplied when using the ZooKeeper based implementation of the
-      RM state store and/or embedded automatic failover in a HA setting.
+      RM state store and/or embedded automatic failover in an HA setting.
     </description>
     <name>yarn.resourcemanager.zk-address</name>
     <!--value>127.0.0.1:2181</value-->
@@ -476,7 +476,7 @@
 
   <property>
     <description>
-      ACLs to be used for the root znode when using ZKRMStateStore in a HA
+      ACLs to be used for the root znode when using ZKRMStateStore in an HA
       scenario for fencing.
 
       ZKRMStateStore supports implicit fencing to allow a single
@@ -602,7 +602,7 @@
   </property>
 
   <property>
-    <description>Name of the cluster. In a HA setting,
+    <description>Name of the cluster. In an HA setting,
       this is used to ensure the RM participates in leader
       election for this cluster and ensures it does not affect
       other clusters</description>
@@ -2172,7 +2172,7 @@
   <property>
     <name>yarn.timeline-service.client.fd-retain-secs</name>
     <description>
-      How long the ATS v1.5 writer will keep a FSStream open.
+      How long the ATS v1.5 writer will keep an FSStream open.
       If this fsstream does not write anything for this configured time,
       it will be close.
     </description>

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/recovery/FileSystemRMStateStore.java

@@ -745,7 +745,7 @@ public class FileSystemRMStateStore extends RMStateStore {
         try {
           return run();
         } catch (IOException e) {
-          LOG.info("Exception while executing a FS operation.", e);
+          LOG.info("Exception while executing an FS operation.", e);
           if (++retry > fsNumRetries) {
             LOG.info("Maxed out FS retries. Giving up!");
             throw e;

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/FSQueueMetrics.java

@@ -200,7 +200,7 @@ public class FSQueueMetrics extends QueueMetrics {
    * @param parent parent queue
    * @param enableUserMetrics  if user metrics is needed
    * @param conf configuration
-   * @return a FSQueueMetrics object
+   * @return an FSQueueMetrics object
    */
   @VisibleForTesting
   public synchronized

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-tests/src/test/java/org/apache/hadoop/yarn/server/MiniYARNCluster.java

@@ -383,7 +383,7 @@ public class MiniYARNCluster extends CompositeService {
   }
 
   /**
-   * In a HA cluster, go through all the RMs and find the Active RM. In a
+   * In an HA cluster, go through all the RMs and find the Active RM. In a
    * non-HA cluster, return the index of the only RM.
    *
    * @return index of the active RM or -1 if none of them turn active