HDFS-16157. Support configuring DNS record to get list of journal nodes contributed by Leon Gao. (#3284)

* Add DNS resolution for QJM

* Add log

* Resolve comments

* checkstyle

* typo

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java

@@ -645,6 +645,17 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
   public static final String  DFS_NAMENODE_EDITS_PLUGIN_PREFIX = "dfs.namenode.edits.journal-plugin";
   public static final String  DFS_NAMENODE_EDITS_DIR_REQUIRED_KEY = "dfs.namenode.edits.dir.required";
   public static final String  DFS_NAMENODE_EDITS_DIR_DEFAULT = "file:///tmp/hadoop/dfs/name";
+
+  public static final String
+      DFS_NAMENODE_EDITS_QJOURNALS_RESOLUTION_ENABLED =
+      "dfs.namenode.edits.qjournals.resolution-enabled";
+  public static final boolean
+      DFS_NAMENODE_EDITS_QJOURNALS_RESOLUTION_ENABLED_DEFAULT = false;
+
+  public static final String
+      DFS_NAMENODE_EDITS_QJOURNALS_RESOLUTION_RESOLVER_IMPL =
+      "dfs.namenode.edits.qjournals.resolver.impl";
+
   public static final String  DFS_METRICS_SESSION_ID_KEY =
       HdfsClientConfigKeys.DeprecatedKeys.DFS_METRICS_SESSION_ID_KEY;
   public static final String  DFS_METRICS_PERCENTILES_INTERVALS_KEY = "dfs.metrics.percentiles.intervals";

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSUtil.java

@@ -490,7 +490,7 @@ public static Set<String> getJournalNodeAddresses(
                     " to append it with namenodeId");
                 URI uri = new URI(journalsUri);
                 List<InetSocketAddress> socketAddresses = Util.
-                    getAddressesList(uri);
+                    getAddressesList(uri, conf);
                 for (InetSocketAddress is : socketAddresses) {
                   journalNodeList.add(is.getHostName());
                 }
@@ -501,7 +501,7 @@ public static Set<String> getJournalNodeAddresses(
           } else {
             URI uri = new URI(journalsUri);
             List<InetSocketAddress> socketAddresses = Util.
-                getAddressesList(uri);
+                getAddressesList(uri, conf);
             for (InetSocketAddress is : socketAddresses) {
               journalNodeList.add(is.getHostName());
             }
@@ -512,7 +512,7 @@ public static Set<String> getJournalNodeAddresses(
           return journalNodeList;
         } else {
           URI uri = new URI(journalsUri);
-          List<InetSocketAddress> socketAddresses = Util.getAddressesList(uri);
+          List<InetSocketAddress> socketAddresses = Util.getAddressesList(uri, conf);
           for (InetSocketAddress is : socketAddresses) {
             journalNodeList.add(is.getHostName());
           }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/qjournal/client/QuorumJournalManager.java

@@ -414,7 +414,7 @@ static List<AsyncLogger> createLoggers(Configuration conf,
                                          String nameServiceId)
       throws IOException {
     List<AsyncLogger> ret = Lists.newArrayList();
-    List<InetSocketAddress> addrs = Util.getAddressesList(uri);
+    List<InetSocketAddress> addrs = Util.getAddressesList(uri, conf);
     if (addrs.size() % 2 == 0) {
       LOG.warn("Quorum journal URI '" + uri + "' has an even number " +
           "of Journal Nodes specified. This is not recommended!");

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/qjournal/server/JournalNodeSyncer.java

@@ -315,7 +315,7 @@ private List<InetSocketAddress> getJournalAddrList(String uriStr) throws
       IOException {
     URI uri = new URI(uriStr);
     return Util.getLoggerAddresses(uri,
-        Sets.newHashSet(jn.getBoundIpcAddress()));
+        Sets.newHashSet(jn.getBoundIpcAddress()), conf);
   }
 
   private void getMissingLogSegments(List<RemoteEditLog> thisJournalEditLogs,

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/common/Util.java

@@ -43,6 +43,8 @@
 import org.apache.hadoop.hdfs.server.namenode.ImageServlet;
 import org.apache.hadoop.hdfs.util.DataTransferThrottler;
 import org.apache.hadoop.io.MD5Hash;
+import org.apache.hadoop.net.DomainNameResolver;
+import org.apache.hadoop.net.DomainNameResolverFactory;
 import org.apache.hadoop.net.NetUtils;
 import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.security.authentication.client.AuthenticationException;
@@ -361,7 +363,7 @@ private static MD5Hash parseMD5Header(HttpURLConnection connection) {
     return (header != null) ? new MD5Hash(header) : null;
   }
 
-  public static List<InetSocketAddress> getAddressesList(URI uri)
+  public static List<InetSocketAddress> getAddressesList(URI uri, Configuration conf)
       throws IOException{
     String authority = uri.getAuthority();
     Preconditions.checkArgument(authority != null && !authority.isEmpty(),
@@ -372,8 +374,35 @@ public static List<InetSocketAddress> getAddressesList(URI uri)
       parts[i] = parts[i].trim();
     }
 
+    boolean resolveNeeded = conf.getBoolean(
+        DFSConfigKeys.DFS_NAMENODE_EDITS_QJOURNALS_RESOLUTION_ENABLED,
+        DFSConfigKeys.DFS_NAMENODE_EDITS_QJOURNALS_RESOLUTION_ENABLED_DEFAULT);
+    DomainNameResolver dnr = DomainNameResolverFactory.newInstance(
+        conf,
+        DFSConfigKeys.DFS_NAMENODE_EDITS_QJOURNALS_RESOLUTION_RESOLVER_IMPL);
+
     List<InetSocketAddress> addrs = Lists.newArrayList();
     for (String addr : parts) {
+      if (resolveNeeded) {
+        LOG.info("Resolving journal address: " + addr);
+        InetSocketAddress isa = NetUtils.createSocketAddr(
+            addr, DFSConfigKeys.DFS_JOURNALNODE_RPC_PORT_DEFAULT);
+        // Get multiple hostnames from domain name if needed,
+        // for example multiple hosts behind a DNS entry.
+        int port = isa.getPort();
+        // QJM should just use FQDN
+        String[] hostnames = dnr
+            .getAllResolvedHostnameByDomainName(isa.getHostName(), true);
+        if (hostnames.length == 0) {
+          throw new UnknownHostException(addr);
+        }
+        for (String h : hostnames) {
+          addrs.add(NetUtils.createSocketAddr(
+              h + ":" + port,
+              DFSConfigKeys.DFS_JOURNALNODE_RPC_PORT_DEFAULT)
+          );
+        }
+      } else {
         InetSocketAddress isa = NetUtils.createSocketAddr(
             addr, DFSConfigKeys.DFS_JOURNALNODE_RPC_PORT_DEFAULT);
         if (isa.isUnresolved()) {
@@ -381,12 +410,13 @@ public static List<InetSocketAddress> getAddressesList(URI uri)
         }
         addrs.add(isa);
       }
+    }
     return addrs;
   }
 
   public static List<InetSocketAddress> getLoggerAddresses(URI uri,
-      Set<InetSocketAddress> addrsToExclude) throws IOException {
+      Set<InetSocketAddress> addrsToExclude, Configuration conf) throws IOException {
-    List<InetSocketAddress> addrsList = getAddressesList(uri);
+    List<InetSocketAddress> addrsList = getAddressesList(uri, conf);
     addrsList.removeAll(addrsToExclude);
     return addrsList;
   }

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

@@ -502,6 +502,25 @@
   <value>org.apache.hadoop.hdfs.qjournal.client.QuorumJournalManager</value>
 </property>
 
+<property>
+  <name>dfs.namenode.edits.qjournals.resolution-enabled</name>
+  <value>false</value>
+  <description>
+    Determines if the given qjournals address is a domain name which needs to
+    be resolved.
+    This is used by namenode to resolve qjournals.
+  </description>
+</property>
+
+<property>
+  <name>dfs.namenode.edits.qjournals.resolver.impl</name>
+  <value></value>
+  <description>
+    Qjournals resolver implementation used by namenode.
+    Effective with dfs.namenode.edits.qjournals.resolution-enabled on.
+  </description>
+</property>
+
 <property>
   <name>dfs.permissions.enabled</name>
   <value>true</value>

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

@@ -194,6 +194,15 @@ The order in which you set these configurations is unimportant, but the values y
           <value>qjournal://node1.example.com:8485;node2.example.com:8485;node3.example.com:8485/mycluster</value>
         </property>
 
+    You can also configure journal nodes by setting up dns round-robin record to avoid hardcoded names:
+
+        <property>
+          <name>dfs.namenode.edits.qjournals.resolution-enabled</name>
+          <value>true</value>
+        </property>
+
+    This will require you to configure multiple IPs behind one dns record on the host level, for example round robin DNS.
+
 *   **dfs.client.failover.proxy.provider.[nameservice ID]** - the Java class that HDFS clients use to contact the Active NameNode
 
     Configure the name of the Java class which will be used by the DFS Client to

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/qjournal/client/TestQuorumJournalManager.java

@@ -33,13 +33,17 @@
 import java.io.File;
 import java.io.IOException;
 import java.net.InetSocketAddress;
+import java.net.URI;
 import java.net.URISyntaxException;
 import java.net.URL;
+import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.TimeoutException;
 
+import org.apache.hadoop.hdfs.server.common.Util;
+import org.apache.hadoop.net.MockDomainNameResolver;
 import org.apache.hadoop.util.Lists;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -1124,6 +1128,32 @@ public void testSelectViaRpcAfterJNRestart() throws Exception {
     }
   }
 
+  @Test
+  public void testGetJournalAddressListWithResolution() throws Exception {
+    Configuration configuration = new Configuration();
+    configuration.setBoolean(
+        DFSConfigKeys.DFS_NAMENODE_EDITS_QJOURNALS_RESOLUTION_ENABLED, true);
+    configuration.set(
+        DFSConfigKeys.DFS_NAMENODE_EDITS_QJOURNALS_RESOLUTION_RESOLVER_IMPL,
+        MockDomainNameResolver.class.getName());
+
+    URI uriWithDomain = URI.create("qjournal://"
+        + MockDomainNameResolver.DOMAIN + ":1234" + "/testns");
+    List<InetSocketAddress> result = Util.getAddressesList(uriWithDomain, configuration);
+    assertEquals(2, result.size());
+    assertEquals(new InetSocketAddress(MockDomainNameResolver.FQDN_1, 1234), result.get(0));
+    assertEquals(new InetSocketAddress(MockDomainNameResolver.FQDN_2, 1234), result.get(1));
+
+    uriWithDomain = URI.create("qjournal://"
+        + MockDomainNameResolver.UNKNOW_DOMAIN + ":1234" + "/testns");
+    try{
+      Util.getAddressesList(uriWithDomain, configuration);
+      fail("Should throw unknown host exception.");
+    } catch (UnknownHostException e) {
+      // expected
+    }
+  }
+  
   private QuorumJournalManager createSpyingQJM()
       throws IOException, URISyntaxException {
     AsyncLogger.Factory spyFactory = new AsyncLogger.Factory() {