Add deprecation warning when a system index is followed

x-pack/plugin/ccr/qa/multi-cluster/src/test/java/org/elasticsearch/xpack/ccr/FollowIndexIT.java

@@ -8,21 +8,28 @@
 
 import org.apache.http.client.methods.HttpPost;
 import org.elasticsearch.client.Request;
+import org.elasticsearch.client.RequestOptions;
 import org.elasticsearch.client.Response;
 import org.elasticsearch.client.ResponseException;
 import org.elasticsearch.client.RestClient;
+import org.elasticsearch.client.WarningFailureException;
 import org.elasticsearch.cluster.metadata.DataStream;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.settings.SecureString;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
+import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.repositories.fs.FsRepository;
 import org.elasticsearch.rest.RestStatus;
+import org.elasticsearch.tasks.TaskResultsService;
 
 import java.io.IOException;
+import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
 
+import static org.elasticsearch.common.xcontent.XContentFactory.jsonBuilder;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.emptyOrNullString;
 import static org.hamcrest.Matchers.equalTo;
@@ -235,6 +242,36 @@ public void testFollowSearchableSnapshotsFails() throws Exception {
         }
     }
 
+    public void testFollowSystemIndexTriggersDeprecationWarnings() throws Exception {
+        if ("leader".equals(targetCluster)) {
+            final Request request = new Request("POST", "/" + TaskResultsService.TASK_INDEX + "/_doc/123");
+            XContentBuilder document = jsonBuilder();
+            document.startObject();
+            document.field("completed", true);
+            document.endObject();
+
+            // Avoid throwing a warning exception since we're writing into a system index
+            request.setOptions(RequestOptions.DEFAULT.toBuilder().setWarningsHandler(warnings -> false));
+            request.setJsonEntity(Strings.toString(document));
+            assertOK(adminClient().performRequest(request));
+            ensureGreen(TaskResultsService.TASK_INDEX);
+        } else {
+            final WarningFailureException exception = expectThrows(WarningFailureException.class,
+                () -> followIndex(TaskResultsService.TASK_INDEX, ".tasks-follower"));
+
+            final List<String> warnings = exception.getResponse().getWarnings();
+            boolean expectedWarningMessageFound = warnings.stream()
+                .anyMatch(warning ->
+                    warning.startsWith("Following a system index [" + TaskResultsService.TASK_INDEX) &&
+                        warning.endsWith("will not work in the next major version"));
+            assertThat(
+                "Expected to find a warning about following system indices but the warnings are: " + warnings,
+                expectedWarningMessageFound,
+                equalTo(true)
+            );
+        }
+    }
+
     @Override
     protected Settings restClientSettings() {
         String token = basicAuthHeaderValue("admin", new SecureString("admin-password".toCharArray()));

x-pack/plugin/ccr/src/internalClusterTest/java/org/elasticsearch/xpack/ccr/AutoFollowIT.java

@@ -26,6 +26,7 @@
 import org.elasticsearch.xpack.CcrIntegTestCase;
 import org.elasticsearch.xpack.core.ccr.AutoFollowMetadata;
 import org.elasticsearch.xpack.core.ccr.AutoFollowStats;
+import org.elasticsearch.xpack.core.ccr.CCR;
 import org.elasticsearch.xpack.core.ccr.action.ActivateAutoFollowPatternAction;
 import org.elasticsearch.xpack.core.ccr.action.CcrStatsAction;
 import org.elasticsearch.xpack.core.ccr.action.DeleteAutoFollowPatternAction;
@@ -117,7 +118,7 @@ public void testCleanFollowedLeaderIndexUUIDs() throws Exception {
 
             Metadata metadata = getFollowerCluster().clusterService().state().metadata();
             String leaderIndexUUID = metadata.index("copy-logs-201901")
-                .getCustomData(Ccr.CCR_CUSTOM_METADATA_KEY)
+                .getCustomData(CCR.CCR_CUSTOM_METADATA_KEY)
                 .get(Ccr.CCR_CUSTOM_METADATA_LEADER_INDEX_UUID_KEY);
             AutoFollowMetadata autoFollowMetadata = metadata.custom(AutoFollowMetadata.TYPE);
             assertThat(autoFollowMetadata, notNullValue());

x-pack/plugin/ccr/src/internalClusterTest/java/org/elasticsearch/xpack/ccr/CcrRepositoryIT.java

@@ -59,6 +59,7 @@
 import org.elasticsearch.xpack.ccr.action.repositories.PutCcrRestoreSessionAction;
 import org.elasticsearch.xpack.ccr.repository.CcrRepository;
 import org.elasticsearch.xpack.ccr.repository.CcrRestoreSourceService;
+import org.elasticsearch.xpack.core.ccr.CCR;
 import org.elasticsearch.xpack.core.ccr.action.PutFollowAction;
 
 import java.io.IOException;
@@ -185,7 +186,7 @@ public void testThatRepositoryRecoversEmptyIndexBasedOnLeaderSettings() throws I
         IndexMetadata leaderMetadata = leaderState.getState().metadata().index(leaderIndex);
         IndexMetadata followerMetadata = followerState.getState().metadata().index(followerIndex);
         assertEquals(leaderMetadata.getNumberOfShards(), followerMetadata.getNumberOfShards());
-        Map<String, String> ccrMetadata = followerMetadata.getCustomData(Ccr.CCR_CUSTOM_METADATA_KEY);
+        Map<String, String> ccrMetadata = followerMetadata.getCustomData(CCR.CCR_CUSTOM_METADATA_KEY);
         assertEquals(leaderIndex, ccrMetadata.get(Ccr.CCR_CUSTOM_METADATA_LEADER_INDEX_NAME_KEY));
         assertEquals(leaderMetadata.getIndexUUID(), ccrMetadata.get(Ccr.CCR_CUSTOM_METADATA_LEADER_INDEX_UUID_KEY));
         assertEquals("leader_cluster", ccrMetadata.get(Ccr.CCR_CUSTOM_METADATA_REMOTE_CLUSTER_NAME_KEY));

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

@@ -132,7 +132,6 @@
 public class Ccr extends Plugin implements ActionPlugin, PersistentTaskPlugin, EnginePlugin, RepositoryPlugin, ClusterPlugin {
 
     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";
     public static final String CCR_CUSTOM_METADATA_LEADER_INDEX_NAME_KEY = "leader_index_name";

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

@@ -44,6 +44,7 @@
 import org.elasticsearch.xpack.core.ccr.AutoFollowMetadata;
 import org.elasticsearch.xpack.core.ccr.AutoFollowMetadata.AutoFollowPattern;
 import org.elasticsearch.xpack.core.ccr.AutoFollowStats;
+import org.elasticsearch.xpack.core.ccr.CCR;
 import org.elasticsearch.xpack.core.ccr.action.PutFollowAction;
 import org.elasticsearch.xpack.searchablesnapshots.SearchableSnapshotsConstants;
 
@@ -555,7 +556,7 @@ private static boolean leaderIndexAlreadyFollowed(AutoFollowPattern autoFollowPa
                 // we should let the auto follower attempt to auto follow it, so it can fail later and
                 // it is then visible in the auto follow stats. For example a cluster can just happen to have
                 // an index with the same name as the new follower index.
-                Map<String, String> customData = indexMetadata.getCustomData(Ccr.CCR_CUSTOM_METADATA_KEY);
+                Map<String, String> customData = indexMetadata.getCustomData(CCR.CCR_CUSTOM_METADATA_KEY);
                 if (customData != null) {
                     String recordedLeaderIndexUUID = customData.get(Ccr.CCR_CUSTOM_METADATA_LEADER_INDEX_UUID_KEY);
                     return leaderIndex.getUUID().equals(recordedLeaderIndexUUID);

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

@@ -71,6 +71,7 @@
 import org.elasticsearch.xpack.ccr.action.bulk.BulkShardOperationsAction;
 import org.elasticsearch.xpack.ccr.action.bulk.BulkShardOperationsRequest;
 import org.elasticsearch.xpack.ccr.action.bulk.BulkShardOperationsResponse;
+import org.elasticsearch.xpack.core.ccr.CCR;
 import org.elasticsearch.xpack.core.ccr.action.ShardFollowTask;
 
 import java.util.ArrayList;
@@ -521,7 +522,7 @@ private void logRetentionLeaseFailure(final String retentionLeaseId, final Throw
 
     private String getLeaderShardHistoryUUID(ShardFollowTask params) {
         IndexMetadata followIndexMetadata = clusterService.state().metadata().index(params.getFollowShardId().getIndex());
-        Map<String, String> ccrIndexMetadata = followIndexMetadata.getCustomData(Ccr.CCR_CUSTOM_METADATA_KEY);
+        Map<String, String> ccrIndexMetadata = followIndexMetadata.getCustomData(CCR.CCR_CUSTOM_METADATA_KEY);
         String[] recordedLeaderShardHistoryUUIDs = extractLeaderShardHistoryUUIDs(ccrIndexMetadata);
         return recordedLeaderShardHistoryUUIDs[params.getLeaderShardId().id()];
     }

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

@@ -21,6 +21,7 @@
 import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.TransportService;
 import org.elasticsearch.xpack.ccr.Ccr;
+import org.elasticsearch.xpack.core.ccr.CCR;
 import org.elasticsearch.xpack.core.ccr.action.FollowInfoAction;
 import org.elasticsearch.xpack.core.ccr.action.FollowInfoAction.Response.FollowerInfo;
 import org.elasticsearch.xpack.core.ccr.action.FollowInfoAction.Response.Status;
@@ -65,7 +66,7 @@ static List<FollowerInfo> getFollowInfos(List<String> concreteFollowerIndices, C
 
         for (String index : concreteFollowerIndices) {
             IndexMetadata indexMetadata = state.metadata().index(index);
-            Map<String, String> ccrCustomData = indexMetadata.getCustomData(Ccr.CCR_CUSTOM_METADATA_KEY);
+            Map<String, String> ccrCustomData = indexMetadata.getCustomData(CCR.CCR_CUSTOM_METADATA_KEY);
             if (ccrCustomData != null) {
                 Optional<ShardFollowTask> result;
                 if (persistentTasks != null) {

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

@@ -23,7 +23,7 @@
 import org.elasticsearch.persistent.PersistentTasksService;
 import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.TransportService;
-import org.elasticsearch.xpack.ccr.Ccr;
+import org.elasticsearch.xpack.core.ccr.CCR;
 import org.elasticsearch.xpack.core.ccr.action.PauseFollowAction;
 import org.elasticsearch.xpack.core.ccr.action.ShardFollowTask;
 
@@ -56,7 +56,7 @@ protected void masterOperation(PauseFollowAction.Request request,
             listener.onFailure(new IndexNotFoundException(request.getFollowIndex()));
             return;
         }
-        if (followerIMD.getCustomData(Ccr.CCR_CUSTOM_METADATA_KEY) == null) {
+        if (followerIMD.getCustomData(CCR.CCR_CUSTOM_METADATA_KEY) == null) {
             listener.onFailure(new IllegalArgumentException("index [" + request.getFollowIndex() + "] is not a follower index"));
             return;
         }

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

@@ -27,9 +27,12 @@
 import org.elasticsearch.cluster.metadata.Metadata;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.inject.Inject;
+import org.elasticsearch.common.logging.DeprecationCategory;
+import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.common.settings.IndexScopedSettings;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.concurrent.AbstractRunnable;
+import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.index.Index;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.license.LicenseUtils;
@@ -52,12 +55,14 @@
 import java.util.Locale;
 import java.util.Objects;
 import java.util.function.BiConsumer;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
 public final class TransportPutFollowAction
     extends TransportMasterNodeAction<PutFollowAction.Request, PutFollowAction.Response> {
 
     private static final Logger logger = LogManager.getLogger(TransportPutFollowAction.class);
+    private static final DeprecationLogger deprecationLogger = DeprecationLogger.getLogger(TransportPutFollowAction.class);
 
     private final IndexScopedSettings indexScopedSettings;
     private final Client client;
@@ -135,6 +140,12 @@ private void createFollowerIndex(
             return;
         }
 
+        if (leaderIndexMetadata.isSystem()) {
+            deprecationLogger.deprecate(DeprecationCategory.INDICES,
+                "ccr_follow_system_indices",
+                "Following a system index " + leaderIndexMetadata.getIndex() + " will not work in the next major version"
+            );
+        }
         final Settings replicatedRequestSettings = TransportResumeFollowAction.filter(request.getSettings());
         if (replicatedRequestSettings.isEmpty() == false) {
             final List<String> unknownKeys =
@@ -232,18 +243,21 @@ public void onFailure(Exception e) {
             listener = originalListener;
         }
 
+        final Supplier<ThreadContext.StoredContext> contextSupplier = threadPool.getThreadContext().newRestorableContext(true);
         RestoreClusterStateListener.createAndRegisterListener(clusterService, response, listener.delegateFailure(
             (delegatedListener, restoreSnapshotResponse) -> {
-                RestoreInfo restoreInfo = restoreSnapshotResponse.getRestoreInfo();
-                if (restoreInfo == null) {
-                    // If restoreInfo is null then it is possible there was a master failure during the
-                    // restore.
-                    delegatedListener.onResponse(new PutFollowAction.Response(true, false, false));
-                } else if (restoreInfo.failedShards() == 0) {
-                    initiateFollowing(clientWithHeaders, request, delegatedListener);
-                } else {
-                    assert restoreInfo.failedShards() > 0 : "Should have failed shards";
-                    delegatedListener.onResponse(new PutFollowAction.Response(true, false, false));
+                try (ThreadContext.StoredContext ctx = contextSupplier.get()) {
+                    RestoreInfo restoreInfo = restoreSnapshotResponse.getRestoreInfo();
+                    if (restoreInfo == null) {
+                        // If restoreInfo is null then it is possible there was a master failure during the
+                        // restore.
+                        delegatedListener.onResponse(new PutFollowAction.Response(true, false, false));
+                    } else if (restoreInfo.failedShards() == 0) {
+                        initiateFollowing(clientWithHeaders, request, delegatedListener);
+                    } else {
+                        assert restoreInfo.failedShards() > 0 : "Should have failed shards";
+                        delegatedListener.onResponse(new PutFollowAction.Response(true, false, false));
+                    }
                 }
             }));
     }

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

@@ -48,6 +48,7 @@
 import org.elasticsearch.xpack.ccr.CcrLicenseChecker;
 import org.elasticsearch.xpack.ccr.CcrSettings;
 import org.elasticsearch.xpack.core.ClientHelper;
+import org.elasticsearch.xpack.core.ccr.CCR;
 import org.elasticsearch.xpack.core.ccr.action.FollowParameters;
 import org.elasticsearch.xpack.core.ccr.action.ResumeFollowAction;
 import org.elasticsearch.xpack.core.ccr.action.ShardFollowTask;
@@ -121,7 +122,7 @@ protected void masterOperation(final ResumeFollowAction.Request request,
             return;
         }
 
-        final Map<String, String> ccrMetadata = followerIndexMetadata.getCustomData(Ccr.CCR_CUSTOM_METADATA_KEY);
+        final Map<String, String> ccrMetadata = followerIndexMetadata.getCustomData(CCR.CCR_CUSTOM_METADATA_KEY);
         if (ccrMetadata == null) {
             throw new IllegalArgumentException("follow index ["+ request.getFollowerIndex() + "] does not have ccr metadata");
         }
@@ -183,7 +184,7 @@ static void validate(
         final MapperService followerMapperService) {
         FollowParameters parameters = request.getParameters();
 
-        Map<String, String> ccrIndexMetadata = followIndex.getCustomData(Ccr.CCR_CUSTOM_METADATA_KEY);
+        Map<String, String> ccrIndexMetadata = followIndex.getCustomData(CCR.CCR_CUSTOM_METADATA_KEY);
         if (ccrIndexMetadata == null) {
             throw new IllegalArgumentException("follow index ["+ followIndex.getIndex().getName() + "] does not have ccr metadata");
         }

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

@@ -41,6 +41,7 @@
 import org.elasticsearch.xpack.ccr.Ccr;
 import org.elasticsearch.xpack.ccr.CcrRetentionLeases;
 import org.elasticsearch.xpack.ccr.CcrSettings;
+import org.elasticsearch.xpack.core.ccr.CCR;
 import org.elasticsearch.xpack.core.ccr.action.ShardFollowTask;
 import org.elasticsearch.xpack.core.ccr.action.UnfollowAction;
 
@@ -95,7 +96,7 @@ public void onFailure(final String source, final Exception e) {
             @Override
             public void clusterStateProcessed(final String source, final ClusterState oldState, final ClusterState newState) {
                 final IndexMetadata indexMetadata = oldState.metadata().index(request.getFollowerIndex());
-                final Map<String, String> ccrCustomMetadata = indexMetadata.getCustomData(Ccr.CCR_CUSTOM_METADATA_KEY);
+                final Map<String, String> ccrCustomMetadata = indexMetadata.getCustomData(CCR.CCR_CUSTOM_METADATA_KEY);
                 final String remoteClusterName = ccrCustomMetadata.get(Ccr.CCR_CUSTOM_METADATA_REMOTE_CLUSTER_NAME_KEY);
 
                 final String leaderIndexName = ccrCustomMetadata.get(Ccr.CCR_CUSTOM_METADATA_LEADER_INDEX_NAME_KEY);
@@ -222,7 +223,7 @@ static ClusterState unfollow(String followerIndex, ClusterState current) {
             throw new IndexNotFoundException(followerIndex);
         }
 
-        if (followerIMD.getCustomData(Ccr.CCR_CUSTOM_METADATA_KEY) == null) {
+        if (followerIMD.getCustomData(CCR.CCR_CUSTOM_METADATA_KEY) == null) {
             throw new IllegalArgumentException("index [" + followerIndex + "] is not a follower index");
         }
 
@@ -253,7 +254,7 @@ static ClusterState unfollow(String followerIndex, ClusterState current) {
         newIndexMetadata.settings(builder);
         newIndexMetadata.settingsVersion(followerIMD.getSettingsVersion() + 1);
         // Remove ccr custom metadata
-        newIndexMetadata.removeCustom(Ccr.CCR_CUSTOM_METADATA_KEY);
+        newIndexMetadata.removeCustom(CCR.CCR_CUSTOM_METADATA_KEY);
 
         Metadata newMetadata = Metadata.builder(current.metadata())
             .put(newIndexMetadata)

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

@@ -88,6 +88,7 @@
 import org.elasticsearch.xpack.ccr.action.repositories.GetCcrRestoreFileChunkRequest;
 import org.elasticsearch.xpack.ccr.action.repositories.PutCcrRestoreSessionAction;
 import org.elasticsearch.xpack.ccr.action.repositories.PutCcrRestoreSessionRequest;
+import org.elasticsearch.xpack.core.ccr.CCR;
 
 import java.io.Closeable;
 import java.io.IOException;
@@ -222,7 +223,7 @@ public IndexMetadata getSnapshotIndexMetaData(RepositoryData repositoryData, Sna
         metadata.put(Ccr.CCR_CUSTOM_METADATA_LEADER_INDEX_UUID_KEY, leaderIndexMetadata.getIndexUUID());
         metadata.put(Ccr.CCR_CUSTOM_METADATA_LEADER_INDEX_NAME_KEY, leaderIndexMetadata.getIndex().getName());
         metadata.put(Ccr.CCR_CUSTOM_METADATA_REMOTE_CLUSTER_NAME_KEY, remoteClusterAlias);
-        imdBuilder.putCustom(Ccr.CCR_CUSTOM_METADATA_KEY, metadata);
+        imdBuilder.putCustom(CCR.CCR_CUSTOM_METADATA_KEY, metadata);
 
         imdBuilder.settings(leaderIndexMetadata.getSettings());
 
@@ -343,7 +344,7 @@ public void restoreShard(Store store, SnapshotId snapshotId, IndexId indexId, Sh
             // TODO: Add timeouts to network calls / the restore process.
             createEmptyStore(store);
 
-            final Map<String, String> ccrMetadata = store.indexSettings().getIndexMetadata().getCustomData(Ccr.CCR_CUSTOM_METADATA_KEY);
+            final Map<String, String> ccrMetadata = store.indexSettings().getIndexMetadata().getCustomData(CCR.CCR_CUSTOM_METADATA_KEY);
             final String leaderIndexName = ccrMetadata.get(Ccr.CCR_CUSTOM_METADATA_LEADER_INDEX_NAME_KEY);
             final String leaderUUID = ccrMetadata.get(Ccr.CCR_CUSTOM_METADATA_LEADER_INDEX_UUID_KEY);
             final Index leaderIndex = new Index(leaderIndexName, leaderUUID);