remove v6.8.x version constant and the backcompat code that uses it

server/src/main/java/org/elasticsearch/ElasticsearchException.java

@@ -1027,7 +1027,7 @@ private enum ElasticsearchExceptionHandle {
                 org.elasticsearch.index.shard.ShardNotInPrimaryModeException.class,
                 org.elasticsearch.index.shard.ShardNotInPrimaryModeException::new,
                 155,
-                Version.V_6_8_1);
+                UNKNOWN_VERSION_ADDED);
 
         final Class<? extends ElasticsearchException> exceptionClass;
         final CheckedFunction<StreamInput, ? extends ElasticsearchException, IOException> constructor;

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

@@ -46,10 +46,6 @@ public class Version implements Comparable<Version>, ToXContentFragment {
      */
     public static final int V_EMPTY_ID = 0;
     public static final Version V_EMPTY = new Version(V_EMPTY_ID, org.apache.lucene.util.Version.LATEST);
-    public static final int V_6_8_0_ID = 6080099;
-    public static final Version V_6_8_0 = new Version(V_6_8_0_ID, org.apache.lucene.util.Version.LUCENE_7_7_0);
-    public static final int V_6_8_1_ID = 6080199;
-    public static final Version V_6_8_1 = new Version(V_6_8_1_ID, org.apache.lucene.util.Version.LUCENE_7_7_0);
     public static final int V_7_0_0_ID = 7000099;
     public static final Version V_7_0_0 = new Version(V_7_0_0_ID, org.apache.lucene.util.Version.LUCENE_8_0_0);
     public static final int V_7_0_1_ID = 7000199;
@@ -96,10 +92,6 @@ public static Version fromId(int id) {
                 return V_7_0_1;
             case V_7_0_0_ID:
                 return V_7_0_0;
-            case V_6_8_1_ID:
-                return V_6_8_1;
-            case V_6_8_0_ID:
-                return V_6_8_0;
             case V_EMPTY_ID:
                 return V_EMPTY;
             default:
@@ -283,8 +275,11 @@ public Version minimumCompatibilityVersion() {
         if (major == 6) {
             // force the minimum compatibility for version 6 to 5.6 since we don't reference version 5 anymore
             return Version.fromId(5060099);
-        } else if (major >= 7) {
-            // all major versions from 7 onwards are compatible with last minor series of the previous major
+        } else if (major == 7) {
+            // force the minimum compatibility for version 7 to 6.8 since we don't reference version 6 anymore
+            return Version.fromId(6080099);
+        } else if (major >= 8) {
+            // all major versions from 8 onwards are compatible with last minor series of the previous major
             Version bwcVersion = null;
 
             for (int i = DeclaredVersionsHolder.DECLARED_VERSIONS.size() - 1; i >= 0; i--) {

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

@@ -186,7 +186,7 @@ public void testMinCompatVersion() {
 
         // from 7.0 on we are supporting the latest minor of the previous major... this might fail once we add a new version ie. 5.x is
         // released since we need to bump the supported minor in Version#minimumCompatibilityVersion()
-        Version lastVersion = Version.V_6_8_0; // TODO: remove this once min compat version is a constant instead of method
+        Version lastVersion = Version.fromString("6.8.0"); // TODO: remove this once min compat version is a constant instead of method
         assertEquals(lastVersion.major, Version.V_7_0_0.minimumCompatibilityVersion().major);
         assertEquals("did you miss to bump the minor in Version#minimumCompatibilityVersion()",
                 lastVersion.minor, Version.V_7_0_0.minimumCompatibilityVersion().minor);
@@ -345,7 +345,7 @@ public static void assertUnknownVersion(Version version) {
 
     public void testIsCompatible() {
         assertTrue(isCompatible(Version.CURRENT, Version.CURRENT.minimumCompatibilityVersion()));
-        assertFalse(isCompatible(Version.fromString("6.7.0"), Version.fromString("7.0.0")));
+        assertFalse(isCompatible(Version.V_7_0_0, Version.V_8_0_0));
         assertTrue(isCompatible(Version.fromString("6.8.0"), Version.fromString("7.0.0")));
         assertFalse(isCompatible(Version.fromId(2000099), Version.V_7_0_0));
         assertFalse(isCompatible(Version.fromId(2000099), Version.fromString("6.5.0")));

server/src/test/java/org/elasticsearch/cluster/coordination/JoinTaskExecutorTests.java

@@ -54,8 +54,7 @@ public void testPreventJoinClusterWithUnsupportedIndices() {
         Settings.builder().build();
         MetaData.Builder metaBuilder = MetaData.builder();
         IndexMetaData indexMetaData = IndexMetaData.builder("test")
-            .settings(settings(VersionUtils.getPreviousVersion(Version.CURRENT
-                .minimumIndexCompatibilityVersion())))
+            .settings(settings(Version.fromString("6.8.0"))) // latest V6 released version
             .numberOfShards(1)
             .numberOfReplicas(1).build();
         metaBuilder.put(indexMetaData, false);

server/src/test/java/org/elasticsearch/cluster/metadata/MetaDataCreateIndexServiceTests.java

@@ -433,12 +433,6 @@ public void testCalculateNumRoutingShards() {
         assertEquals(2048, MetaDataCreateIndexService.calculateNumRoutingShards(1024, Version.CURRENT));
         assertEquals(4096, MetaDataCreateIndexService.calculateNumRoutingShards(2048, Version.CURRENT));
 
-        Version latestV6 = VersionUtils.getPreviousVersion(Version.V_7_0_0);
-        int numShards = randomIntBetween(1, 1000);
-        assertEquals(numShards, MetaDataCreateIndexService.calculateNumRoutingShards(numShards, latestV6));
-        assertEquals(numShards, MetaDataCreateIndexService.calculateNumRoutingShards(numShards,
-            VersionUtils.randomVersionBetween(random(), VersionUtils.getFirstVersion(), latestV6)));
-
         for (int i = 0; i < 1000; i++) {
             int randomNumShards = randomIntBetween(1, 10000);
             int numRoutingShards = MetaDataCreateIndexService.calculateNumRoutingShards(randomNumShards, Version.CURRENT);

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/SecurityTests.java

@@ -318,29 +318,6 @@ public void testJoinValidatorForFIPSLicense() throws Exception {
         }
     }
 
-    public void testIndexJoinValidator_Old_And_Rolling() throws Exception {
-        createComponents(Settings.EMPTY);
-        BiConsumer<DiscoveryNode, ClusterState> joinValidator = security.getJoinValidator();
-        assertNotNull(joinValidator);
-        Version version = VersionUtils.randomVersionBetween(random(), VersionUtils.getFirstVersion(),
-            VersionUtils.getPreviousVersion(Version.V_7_0_0));
-        DiscoveryNode node = new DiscoveryNode("foo", buildNewFakeTransportAddress(), Version.CURRENT);
-        IndexMetaData indexMetaData = IndexMetaData.builder(SECURITY_MAIN_ALIAS)
-            .settings(settings(version)
-                .put(INDEX_FORMAT_SETTING.getKey(), INTERNAL_MAIN_INDEX_FORMAT - 1))
-            .numberOfShards(1).numberOfReplicas(0)
-            .build();
-        DiscoveryNode existingOtherNode = new DiscoveryNode("bar", buildNewFakeTransportAddress(), version);
-        DiscoveryNodes discoveryNodes = DiscoveryNodes.builder().add(existingOtherNode).build();
-        ClusterState clusterState = ClusterState.builder(ClusterName.DEFAULT)
-            .nodes(discoveryNodes)
-            .metaData(MetaData.builder().put(indexMetaData, true).build()).build();
-        IllegalStateException e = expectThrows(IllegalStateException.class,
-            () -> joinValidator.accept(node, clusterState));
-        assertThat(e.getMessage(), equalTo("Security index is not on the current version [6] - " +
-            "The Upgrade API must be run for 7.x nodes to join the cluster"));
-    }
-
     public void testIndexJoinValidator_FullyCurrentCluster() throws Exception {
         createComponents(Settings.EMPTY);
         BiConsumer<DiscoveryNode, ClusterState> joinValidator = security.getJoinValidator();