Remove usage or `InetAddress#getLocalHost`

this method is very confusing and if it's used it's likely the wrong thing
with respect to the actual bound / published address. This change discourages
it's use and removes all useage. It's replaced with the actual published address
most of the time.

core/src/main/java/org/elasticsearch/cluster/node/DiscoveryNode.java

@@ -138,7 +138,7 @@ public class DiscoveryNode implements Streamable, ToXContent {
      * @param version    the version of the node.
      */
     public DiscoveryNode(String nodeName, String nodeId, TransportAddress address, Map<String, String> attributes, Version version) {
-        this(nodeName, nodeId, NetworkUtils.getLocalHost().getHostName(), NetworkUtils.getLocalHost().getHostAddress(), address, attributes, version);
+        this(nodeName, nodeId, address.getHost(), address.getAddress(), address, attributes, version);
     }
 
     /**

core/src/main/java/org/elasticsearch/cluster/service/InternalClusterService.java

@@ -40,6 +40,8 @@ import org.elasticsearch.common.logging.ESLogger;
 import org.elasticsearch.common.logging.Loggers;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.text.StringText;
+import org.elasticsearch.common.transport.BoundTransportAddress;
+import org.elasticsearch.common.transport.TransportAddress;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.util.concurrent.*;
 import org.elasticsearch.discovery.Discovery;
@@ -159,7 +161,8 @@ public class InternalClusterService extends AbstractLifecycleComponent<ClusterSe
         Map<String, String> nodeAttributes = discoveryNodeService.buildAttributes();
         // note, we rely on the fact that its a new id each time we start, see FD and "kill -9" handling
         final String nodeId = DiscoveryService.generateNodeId(settings);
-        DiscoveryNode localNode = new DiscoveryNode(settings.get("name"), nodeId, transportService.boundAddress().publishAddress(), nodeAttributes, version);
+        final TransportAddress publishAddress = transportService.boundAddress().publishAddress();
+        DiscoveryNode localNode = new DiscoveryNode(settings.get("name"), nodeId, publishAddress, nodeAttributes, version);
         DiscoveryNodes.Builder nodeBuilder = DiscoveryNodes.builder().put(localNode).localNodeId(localNode.id());
         this.clusterState = ClusterState.builder(clusterState).nodes(nodeBuilder).blocks(initialBlocks).build();
         this.transportService.setLocalNode(localNode);

core/src/main/java/org/elasticsearch/common/network/NetworkUtils.java

@@ -127,17 +127,6 @@ public abstract class NetworkUtils {
         return Constants.WINDOWS ? false : true;
     }
     
-    /** Returns localhost, or if its misconfigured, falls back to loopback. Use with caution!!!! */
-    // TODO: can we remove this?
-    public static InetAddress getLocalHost() {
-        try {
-            return InetAddress.getLocalHost();
-        } catch (UnknownHostException e) {
-            logger.warn("failed to resolve local host, fallback to loopback", e);
-            return InetAddress.getLoopbackAddress();
-        }
-    }
-    
     /** Returns addresses for all loopback interfaces that are up. */
     public static InetAddress[] getLoopbackAddresses() throws SocketException {
         List<InetAddress> list = new ArrayList<>();

core/src/main/java/org/elasticsearch/common/transport/DummyTransportAddress.java

@@ -44,6 +44,21 @@ public class DummyTransportAddress implements TransportAddress {
         return other == INSTANCE;
     }
 
+    @Override
+    public String getHost() {
+        return "dummy";
+    }
+
+    @Override
+    public String getAddress() {
+        return "0.0.0.0"; // see https://en.wikipedia.org/wiki/0.0.0.0
+    }
+
+    @Override
+    public int getPort() {
+        return 42;
+    }
+
     @Override
     public DummyTransportAddress readFrom(StreamInput in) throws IOException {
         return INSTANCE;

core/src/main/java/org/elasticsearch/common/transport/InetSocketTransportAddress.java

@@ -30,7 +30,7 @@ import java.net.InetSocketAddress;
 /**
  * A transport address used for IP socket address (wraps {@link java.net.InetSocketAddress}).
  */
-public class InetSocketTransportAddress implements TransportAddress {
+public final class InetSocketTransportAddress implements TransportAddress {
 
     private static boolean resolveAddress = false;
 
@@ -92,6 +92,21 @@ public class InetSocketTransportAddress implements TransportAddress {
                 address.getAddress().equals(((InetSocketTransportAddress) other).address.getAddress());
     }
 
+    @Override
+    public String getHost() {
+        return address.getHostName();
+    }
+
+    @Override
+    public String getAddress() {
+        return address.getAddress().getHostAddress();
+    }
+
+    @Override
+    public int getPort() {
+        return address.getPort();
+    }
+
     public InetSocketAddress address() {
         return this.address;
     }

core/src/main/java/org/elasticsearch/common/transport/LocalTransportAddress.java

@@ -29,7 +29,7 @@ import java.io.IOException;
 /**
  *
  */
-public class LocalTransportAddress implements TransportAddress {
+public final class LocalTransportAddress implements TransportAddress {
 
     public static final LocalTransportAddress PROTO = new LocalTransportAddress("_na");
 
@@ -57,6 +57,21 @@ public class LocalTransportAddress implements TransportAddress {
         return other instanceof LocalTransportAddress && id.equals(((LocalTransportAddress) other).id);
     }
 
+    @Override
+    public String getHost() {
+        return "local";
+    }
+
+    @Override
+    public String getAddress() {
+        return "0.0.0.0"; // see https://en.wikipedia.org/wiki/0.0.0.0
+    }
+
+    @Override
+    public int getPort() {
+        return 0;
+    }
+
     @Override
     public LocalTransportAddress readFrom(StreamInput in) throws IOException {
         return new LocalTransportAddress(in);

core/src/main/java/org/elasticsearch/common/transport/TransportAddress.java

@@ -28,7 +28,24 @@ import org.elasticsearch.common.io.stream.Writeable;
  */
 public interface TransportAddress extends Writeable<TransportAddress> {
 
+    /**
+     * Returns the host string for this transport address
+     */
+    String getHost();
+
+    /**
+     * Returns the address string for this transport address
+     */
+    String getAddress();
+
+    /**
+     * Returns the port of this transport address if applicable
+     */
+    int getPort();
+
     short uniqueAddressTypeId();
 
     boolean sameHost(TransportAddress other);
+
+    public String toString();
 }

core/src/test/java/org/elasticsearch/cluster/routing/allocation/decider/MockDiskUsagesIT.java

@@ -27,6 +27,7 @@ import org.elasticsearch.cluster.*;
 import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.cluster.routing.RoutingNode;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.transport.DummyTransportAddress;
 import org.elasticsearch.monitor.fs.FsInfo;
 import org.elasticsearch.test.ESIntegTestCase;
 import org.junit.Test;
@@ -167,7 +168,7 @@ public class MockDiskUsagesIT extends ESIntegTestCase {
                 usage.getTotalBytes(), usage.getFreeBytes(), usage.getFreeBytes());
         paths[0] = path;
         FsInfo fsInfo = new FsInfo(System.currentTimeMillis(), paths);
-        return new NodeStats(new DiscoveryNode(nodeName, null, Version.V_2_0_0_beta1),
+        return new NodeStats(new DiscoveryNode(nodeName, DummyTransportAddress.INSTANCE, Version.CURRENT),
                 System.currentTimeMillis(),
                 null, null, null, null, null,
                 fsInfo,

core/src/test/java/org/elasticsearch/test/InternalTestCluster.java

@@ -108,6 +108,7 @@ import org.junit.Assert;
 
 import java.io.Closeable;
 import java.io.IOException;
+import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.nio.file.Path;
 import java.util.ArrayList;
@@ -504,7 +505,6 @@ public final class InternalTestCluster extends TestCluster {
     public static String clusterName(String prefix, long clusterSeed) {
         StringBuilder builder = new StringBuilder(prefix);
         final int childVM = RandomizedTest.systemPropertyAsInt(SysGlobals.CHILDVM_SYSPROP_JVM_ID, 0);
-        builder.append('-').append(NetworkUtils.getLocalHost().getHostName());
         builder.append("-CHILD_VM=[").append(childVM).append(']');
         builder.append("-CLUSTER_SEED=[").append(clusterSeed).append(']');
         // if multiple maven task run on a single host we better have an identifier that doesn't rely on input params

dev-tools/src/main/resources/forbidden/all-signatures.txt

@@ -18,6 +18,9 @@
 java.net.URL#getPath()
 java.net.URL#getFile()
 
+@defaultMessage Usage of getLocalHost is discouraged
+java.net.InetAddress#getLocalHost()
+
 @defaultMessage Use java.nio.file instead of java.io.File API
 java.util.jar.JarFile
 java.util.zip.ZipFile