[CCR] Add metadata to keep track of the index uuid of the leader index in the follow index (#33367)

The follow index api checks if the recorded uuid in the follow index matches
with uuid of the leader index and fails otherwise. This validation will
prevent a follow index from following an incompatible leader index.

The create_and_follow api will automatically add this custom index metadata
when it creates the follow index.

Closes #31505

Author: martijnvg

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/Ccr.java

@@ -88,6 +88,7 @@ public class Ccr extends Plugin implements ActionPlugin, PersistentTaskPlugin, E
     public static final String CCR_THREAD_POOL_NAME = "ccr";
     public static final String CCR_CUSTOM_METADATA_KEY = "ccr";
     public static final String CCR_CUSTOM_METADATA_LEADER_INDEX_SHARD_HISTORY_UUIDS = "leader_index_shard_history_uuids";
+    public static final String CCR_CUSTOM_METADATA_LEADER_INDEX_UUID_KEY = "leader_index_uuid";
 
     private final boolean enabled;
     private final Settings settings;

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/action/TransportCreateAndFollowIndexAction.java

@@ -183,6 +183,7 @@ public ClusterState execute(final ClusterState currentState) throws Exception {
                 // Adding the leader index uuid for each shard as custom metadata:
                 Map<String, String> metadata = new HashMap<>();
                 metadata.put(Ccr.CCR_CUSTOM_METADATA_LEADER_INDEX_SHARD_HISTORY_UUIDS, String.join(",", historyUUIDs));
+                metadata.put(Ccr.CCR_CUSTOM_METADATA_LEADER_INDEX_UUID_KEY, leaderIndexMetaData.getIndexUUID());
                 imdBuilder.putCustom(Ccr.CCR_CUSTOM_METADATA_KEY, metadata);
 
                 // Copy all settings, but overwrite a few settings.

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/action/TransportFollowIndexAction.java

@@ -251,6 +251,14 @@ static void validate(
         if (followIndex == null) {
             throw new IllegalArgumentException("follow index [" + request.getFollowerIndex() + "] does not exist");
         }
+        String leaderIndexUUID = leaderIndex.getIndex().getUUID();
+        String recordedLeaderIndexUUID = followIndex
+                .getCustomData(Ccr.CCR_CUSTOM_METADATA_KEY)
+                .get(Ccr.CCR_CUSTOM_METADATA_LEADER_INDEX_UUID_KEY);
+        if (leaderIndexUUID.equals(recordedLeaderIndexUUID) == false) {
+            throw new IllegalArgumentException("follow index [" + request.getFollowerIndex() + "] should reference [" + leaderIndexUUID +
+                    "] as leader index but instead reference [" + recordedLeaderIndexUUID + "] as leader index");
+        }
 
         String[] recordedHistoryUUIDs = extractIndexShardHistoryUUIDs(followIndex);
         assert recordedHistoryUUIDs.length == leaderIndexHistoryUUID.length;

x-pack/plugin/ccr/src/test/java/org/elasticsearch/xpack/ccr/ShardChangesIT.java

@@ -17,7 +17,6 @@
 import org.elasticsearch.action.index.IndexRequest;
 import org.elasticsearch.action.search.SearchRequest;
 import org.elasticsearch.action.search.SearchResponse;
-import org.elasticsearch.action.support.ActiveShardCount;
 import org.elasticsearch.analysis.common.CommonAnalysisPlugin;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.metadata.MappingMetaData;
@@ -313,10 +312,7 @@ public void testFollowIndexAndCloseNode() throws Exception {
         internalCluster().ensureAtLeastNumDataNodes(3);
         String leaderIndexSettings = getIndexSettings(3, 1, singletonMap(IndexSettings.INDEX_SOFT_DELETES_SETTING.getKey(), "true"));
         assertAcked(client().admin().indices().prepareCreate("index1").setSource(leaderIndexSettings, XContentType.JSON));
-
-        String followerIndexSettings = getIndexSettings(3, 1, singletonMap(CcrSettings.CCR_FOLLOWING_INDEX_SETTING.getKey(), "true"));
-        assertAcked(client().admin().indices().prepareCreate("index2").setSource(followerIndexSettings, XContentType.JSON));
-        ensureGreen("index1", "index2");
+        ensureGreen("index1");
 
         AtomicBoolean run = new AtomicBoolean(true);
         Thread thread = new Thread(() -> {
@@ -338,7 +334,7 @@ public void testFollowIndexAndCloseNode() throws Exception {
         final FollowIndexAction.Request followRequest = new FollowIndexAction.Request("index1", "index2", randomIntBetween(32, 2048),
             randomIntBetween(2, 10), Long.MAX_VALUE, randomIntBetween(2, 10),
             FollowIndexAction.DEFAULT_MAX_WRITE_BUFFER_SIZE, TimeValue.timeValueMillis(500), TimeValue.timeValueMillis(10));
-        client().execute(FollowIndexAction.INSTANCE, followRequest).get();
+        client().execute(CreateAndFollowIndexAction.INSTANCE, new CreateAndFollowIndexAction.Request(followRequest)).get();
 
         long maxNumDocsReplicated = Math.min(1000, randomLongBetween(followRequest.getMaxBatchOperationCount(),
             followRequest.getMaxBatchOperationCount() * 10));
@@ -415,33 +411,6 @@ public void testFollowNonExistentIndex() throws Exception {
         expectThrows(IndexNotFoundException.class, () -> client().execute(FollowIndexAction.INSTANCE, followRequest3).actionGet());
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/33379")
-    public void testValidateFollowingIndexSettings() throws Exception {
-        assertAcked(client().admin().indices().prepareCreate("test-leader")
-            .setSettings(Settings.builder().put(IndexSettings.INDEX_SOFT_DELETES_SETTING.getKey(), true)));
-        // TODO: indexing should be optional but the current mapping logic requires for now.
-        client().prepareIndex("test-leader", "doc", "id").setSource("{\"f\": \"v\"}", XContentType.JSON).get();
-        assertAcked(client().admin().indices().prepareCreate("test-follower").get());
-        IllegalArgumentException followError = expectThrows(IllegalArgumentException.class, () -> client().execute(
-            FollowIndexAction.INSTANCE, createFollowRequest("test-leader", "test-follower")).actionGet());
-        assertThat(followError.getMessage(), equalTo("the following index [test-follower] is not ready to follow;" +
-            " the setting [index.xpack.ccr.following_index] must be enabled."));
-        // updating the `following_index` with an open index must not be allowed.
-        IllegalArgumentException updateError = expectThrows(IllegalArgumentException.class, () -> {
-            client().admin().indices().prepareUpdateSettings("test-follower")
-                .setSettings(Settings.builder().put(CcrSettings.CCR_FOLLOWING_INDEX_SETTING.getKey(), true)).get();
-        });
-        assertThat(updateError.getMessage(), containsString("Can't update non dynamic settings " +
-            "[[index.xpack.ccr.following_index]] for open indices [[test-follower/"));
-        assertAcked(client().admin().indices().prepareClose("test-follower"));
-        assertAcked(client().admin().indices().prepareUpdateSettings("test-follower")
-            .setSettings(Settings.builder().put(CcrSettings.CCR_FOLLOWING_INDEX_SETTING.getKey(), true)));
-        assertAcked(client().admin().indices().prepareOpen("test-follower").setWaitForActiveShards(ActiveShardCount.DEFAULT));
-        assertAcked(client().execute(FollowIndexAction.INSTANCE,
-            createFollowRequest("test-leader", "test-follower")).actionGet());
-        unfollowIndex("test-follower");
-    }
-
     public void testFollowIndex_lowMaxTranslogBytes() throws Exception {
         final String leaderIndexSettings = getIndexSettings(1, between(0, 1),
             singletonMap(IndexSettings.INDEX_SOFT_DELETES_SETTING.getKey(), "true"));
@@ -476,6 +445,37 @@ public void testFollowIndex_lowMaxTranslogBytes() throws Exception {
         unfollowIndex("index2");
     }
 
+    public void testDontFollowTheWrongIndex() throws Exception {
+        String leaderIndexSettings = getIndexSettings(1, 0,
+            Collections.singletonMap(IndexSettings.INDEX_SOFT_DELETES_SETTING.getKey(), "true"));
+        assertAcked(client().admin().indices().prepareCreate("index1").setSource(leaderIndexSettings, XContentType.JSON));
+        ensureGreen("index1");
+        assertAcked(client().admin().indices().prepareCreate("index3").setSource(leaderIndexSettings, XContentType.JSON));
+        ensureGreen("index3");
+
+        FollowIndexAction.Request followRequest = new FollowIndexAction.Request("index1", "index2", 1024, 1, 1024L,
+            1, 10240, TimeValue.timeValueMillis(500), TimeValue.timeValueMillis(10));
+        CreateAndFollowIndexAction.Request createAndFollowRequest = new CreateAndFollowIndexAction.Request(followRequest);
+        client().execute(CreateAndFollowIndexAction.INSTANCE, createAndFollowRequest).get();
+
+        followRequest = new FollowIndexAction.Request("index3", "index4", 1024, 1, 1024L,
+            1, 10240, TimeValue.timeValueMillis(500), TimeValue.timeValueMillis(10));
+        createAndFollowRequest = new CreateAndFollowIndexAction.Request(followRequest);
+        client().execute(CreateAndFollowIndexAction.INSTANCE, createAndFollowRequest).get();
+        unfollowIndex("index2", "index4");
+
+        FollowIndexAction.Request wrongRequest1 = new FollowIndexAction.Request("index1", "index4", 1024, 1, 1024L,
+            1, 10240, TimeValue.timeValueMillis(500), TimeValue.timeValueMillis(10));
+        Exception e = expectThrows(IllegalArgumentException.class,
+            () -> client().execute(FollowIndexAction.INSTANCE, wrongRequest1).actionGet());
+        assertThat(e.getMessage(), containsString("follow index [index4] should reference"));
+
+        FollowIndexAction.Request wrongRequest2 = new FollowIndexAction.Request("index3", "index2", 1024, 1, 1024L,
+            1, 10240, TimeValue.timeValueMillis(500), TimeValue.timeValueMillis(10));
+        e = expectThrows(IllegalArgumentException.class, () -> client().execute(FollowIndexAction.INSTANCE, wrongRequest2).actionGet());
+        assertThat(e.getMessage(), containsString("follow index [index2] should reference"));
+    }
+
     private CheckedRunnable<Exception> assertTask(final int numberOfPrimaryShards, final Map<ShardId, Long> numDocsPerShard) {
         return () -> {
             final ClusterState clusterState = client().admin().cluster().prepareState().get().getState();
@@ -512,10 +512,12 @@ private CheckedRunnable<Exception> assertTask(final int numberOfPrimaryShards, f
         };
     }
 
-    private void unfollowIndex(String index) throws Exception {
-        final UnfollowIndexAction.Request unfollowRequest = new UnfollowIndexAction.Request();
-        unfollowRequest.setFollowIndex(index);
-        client().execute(UnfollowIndexAction.INSTANCE, unfollowRequest).get();
+    private void unfollowIndex(String... indices) throws Exception {
+        for (String index : indices) {
+            final UnfollowIndexAction.Request unfollowRequest = new UnfollowIndexAction.Request();
+            unfollowRequest.setFollowIndex(index);
+            client().execute(UnfollowIndexAction.INSTANCE, unfollowRequest).get();
+        }
         assertBusy(() -> {
             final ClusterState clusterState = client().admin().cluster().prepareState().get().getState();
             final PersistentTasksCustomMetaData tasks = clusterState.getMetaData().custom(PersistentTasksCustomMetaData.TYPE);