[CLIENT] Unknown node version should be a lower bound

Today when we start a `TransportClient` we use the given transport
addresses and create a `DiscoveryNode` from it without knowing the
actual nodes version. We just use the `Version.CURRENT` which is an
upper bound. Yet, the other node might be a version less than the
currently running and serialisation of the nodes info might break. We
should rather use a lower bound here which is the version of the first
release with the same major version as `Version.CURRENT` since this is
what we officially support.

This commit moves to use the minimum major version or an RC / Snapshot
if the current version is a snapshot.

Closes #6894

src/main/java/org/elasticsearch/Version.java

@@ -453,6 +453,17 @@ public class Version implements Serializable {
         return version.id >= id;
     }
 
+    /**
+     * Returns the minimum compatible version based on the current
+     * version. Ie a node needs to have at least the return version in order
+     * to communicate with a node running the current version. The returned version
+     * is in most of the cases the smallest major version release unless the current version
+     * is a beta or RC release then the version itself is returned.
+     */
+    public Version minimumCompatibilityVersion() {
+        return Version.smallest(this, fromId(major * 1000000 + 99));
+    }
+
     /**
      * Just the version number (without -SNAPSHOT if snapshot).
      */

src/main/java/org/elasticsearch/client/transport/TransportClient.java

@@ -196,6 +196,10 @@ public class TransportClient extends AbstractClient {
         internalClient = injector.getInstance(InternalTransportClient.class);
     }
 
+    TransportClientNodesService nodeService() {
+        return nodesService;
+    }
+
     /**
      * Returns the current registered transport addresses to use (added using
      * {@link #addTransportAddress(org.elasticsearch.common.transport.TransportAddress)}.

src/main/java/org/elasticsearch/client/transport/TransportClientNodesService.java

@@ -67,7 +67,7 @@ public class TransportClientNodesService extends AbstractComponent {
 
     private final ThreadPool threadPool;
 
-    private final Version version;
+    private final Version minCompatibilityVersion;
 
     // nodes that are added to be discovered
     private volatile ImmutableList<DiscoveryNode> listedNodes = ImmutableList.of();
@@ -95,7 +95,7 @@ public class TransportClientNodesService extends AbstractComponent {
         this.clusterName = clusterName;
         this.transportService = transportService;
         this.threadPool = threadPool;
-        this.version = version;
+        this.minCompatibilityVersion = version.minimumCompatibilityVersion();
 
         this.nodesSamplerInterval = componentSettings.getAsTime("nodes_sampler_interval", timeValueSeconds(5));
         this.pingTimeout = componentSettings.getAsTime("ping_timeout", timeValueSeconds(5)).millis();
@@ -161,7 +161,7 @@ public class TransportClientNodesService extends AbstractComponent {
             ImmutableList.Builder<DiscoveryNode> builder = ImmutableList.builder();
             builder.addAll(listedNodes());
             for (TransportAddress transportAddress : filtered) {
-                DiscoveryNode node = new DiscoveryNode("#transport#-" + tempNodeIdGenerator.incrementAndGet(), transportAddress, version);
+                DiscoveryNode node = new DiscoveryNode("#transport#-" + tempNodeIdGenerator.incrementAndGet(), transportAddress, minCompatibilityVersion);
                 logger.debug("adding address [{}]", node);
                 builder.add(node);
             }

src/test/java/org/elasticsearch/VersionTests.java

@@ -104,4 +104,14 @@ public class VersionTests extends ElasticsearchTestCase {
         final Version version = randomFrom(Version.V_0_18_0, Version.V_0_90_13, Version.V_1_3_0);
         assertEquals(version, Version.indexCreated(ImmutableSettings.builder().put(IndexMetaData.SETTING_UUID, "foo").put(IndexMetaData.SETTING_VERSION_CREATED, version).build()));
     }
+
+    @Test
+    public void testMinCompatVersion() {
+        assertThat(Version.V_2_0_0.minimumCompatibilityVersion(), equalTo(Version.V_2_0_0));
+        assertThat(Version.V_1_3_0.minimumCompatibilityVersion(), equalTo(Version.V_1_0_0));
+        assertThat(Version.V_1_2_0.minimumCompatibilityVersion(), equalTo(Version.V_1_0_0));
+        assertThat(Version.V_1_2_3.minimumCompatibilityVersion(), equalTo(Version.V_1_0_0));
+        assertThat(Version.V_1_0_0_RC2.minimumCompatibilityVersion(), equalTo(Version.V_1_0_0_RC2));
+    }
+
 }

src/test/java/org/elasticsearch/client/transport/TransportClientTests.java

@@ -19,13 +19,22 @@
 
 package org.elasticsearch.client.transport;
 
+import org.elasticsearch.Version;
+import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.common.settings.ImmutableSettings;
+import org.elasticsearch.common.transport.TransportAddress;
+import org.elasticsearch.node.Node;
+import org.elasticsearch.node.NodeBuilder;
+import org.elasticsearch.node.internal.InternalNode;
 import org.elasticsearch.test.ElasticsearchIntegrationTest;
 import org.elasticsearch.test.ElasticsearchIntegrationTest.ClusterScope;
-import org.hamcrest.Matchers;
+import org.elasticsearch.transport.TransportService;
 import org.junit.Test;
 
-import static org.elasticsearch.test.ElasticsearchIntegrationTest.*;
+import static org.elasticsearch.test.ElasticsearchIntegrationTest.Scope;
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.greaterThanOrEqualTo;
+import static org.hamcrest.Matchers.startsWith;
 
 @ClusterScope(scope = Scope.TEST, numDataNodes = 0, transportClientRatio = 1.0)
 public class TransportClientTests extends ElasticsearchIntegrationTest {
@@ -35,7 +44,41 @@ public class TransportClientTests extends ElasticsearchIntegrationTest {
         String nodeName = internalCluster().startNode(ImmutableSettings.builder().put("node.data", false));
 
         TransportClient client = (TransportClient) internalCluster().client(nodeName);
-        assertThat(client.connectedNodes().get(0).dataNode(), Matchers.equalTo(false));
+        assertThat(client.connectedNodes().get(0).dataNode(), equalTo(false));
 
     }
+
+    @Test
+    public void testNodeVersionIsUpdated() {
+        TransportClient client = (TransportClient)  internalCluster().client();
+        TransportClientNodesService nodeService = client.nodeService();
+        Node node = NodeBuilder.nodeBuilder().data(false).settings(ImmutableSettings.builder()
+                .put(internalCluster().getDefaultSettings())
+                .put("http.enabled", false)
+                .put("index.store.type", "ram")
+                .put("config.ignore_system_properties", true) // make sure we get what we set :)
+                .put("gateway.type", "none")
+                .build()).clusterName("foobar").build();
+        node.start();
+        try {
+            TransportAddress transportAddress = ((InternalNode) node).injector().getInstance(TransportService.class).boundAddress().publishAddress();
+            client.addTransportAddress(transportAddress);
+            assertThat(nodeService.connectedNodes().size(), greaterThanOrEqualTo(1)); // since we force transport clients there has to be one node started that we connect to.
+            for (DiscoveryNode discoveryNode : nodeService.connectedNodes()) {  // connected nodes have updated version
+                assertThat(discoveryNode.getVersion(), equalTo(Version.CURRENT));
+            }
+
+            for (DiscoveryNode discoveryNode : nodeService.listedNodes()) {
+                assertThat(discoveryNode.id(), startsWith("#transport#-"));
+                assertThat(discoveryNode.getVersion(), equalTo(Version.CURRENT.minimumCompatibilityVersion()));
+            }
+
+            assertThat(nodeService.filteredNodes().size(), equalTo(1));
+            for (DiscoveryNode discoveryNode : nodeService.filteredNodes()) {
+                assertThat(discoveryNode.getVersion(), equalTo(Version.CURRENT.minimumCompatibilityVersion()));
+            }
+        } finally {
+            node.stop();
+        }
+    }
 }