Wildcard cluster names for cross cluster search

core/src/main/java/org/elasticsearch/action/search/RemoteClusterService.java

@@ -25,6 +25,7 @@
 import org.elasticsearch.action.admin.cluster.shards.ClusterSearchShardsGroup;
 import org.elasticsearch.action.admin.cluster.shards.ClusterSearchShardsResponse;
 import org.elasticsearch.action.support.PlainActionFuture;
+import org.elasticsearch.cluster.metadata.ClusterNameExpressionResolver;
 import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.cluster.node.DiscoveryNodes;
 import org.elasticsearch.cluster.routing.PlainShardIterator;
@@ -55,6 +56,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
@@ -111,11 +113,13 @@ public final class RemoteClusterService extends AbstractComponent implements Clo
 
     private final TransportService transportService;
     private final int numRemoteConnections;
+    private final ClusterNameExpressionResolver clusterNameResolver;
     private volatile Map<String, RemoteClusterConnection> remoteClusters = Collections.emptyMap();
 
     RemoteClusterService(Settings settings, TransportService transportService) {
         super(settings);
         this.transportService = transportService;
+        this.clusterNameResolver = new ClusterNameExpressionResolver(settings);
         numRemoteConnections = REMOTE_CONNECTIONS_PER_CLUSTER.get(settings);
     }
 
@@ -203,25 +207,30 @@ boolean isRemoteNodeConnected(final String remoteCluster, final DiscoveryNode no
      */
     Map<String, List<String>> groupClusterIndices(String[] requestIndices, Predicate<String> indexExists) {
         Map<String, List<String>> perClusterIndices = new HashMap<>();
+        Set<String> remoteClusterNames = this.remoteClusters.keySet();
         for (String index : requestIndices) {
             int i = index.indexOf(REMOTE_CLUSTER_INDEX_SEPARATOR);
-            String indexName = index;
-            String clusterName = LOCAL_CLUSTER_GROUP_KEY;
             if (i >= 0) {
                 String remoteClusterName = index.substring(0, i);
-                if (isRemoteClusterRegistered(remoteClusterName)) {
+                List<String> clusters = clusterNameResolver.resolveClusterNames(remoteClusterNames, remoteClusterName);
+                if (clusters.isEmpty()) {
                     if (indexExists.test(index)) {
                         // we use : as a separator for remote clusters. might conflict if there is an index that is actually named
                         // remote_cluster_alias:index_name - for this case we fail the request. the user can easily change the cluster alias
                         // if that happens
                         throw new IllegalArgumentException("Can not filter indices; index " + index +
                             " exists but there is also a remote cluster named: " + remoteClusterName);
+                        }
+                    String indexName = index.substring(i + 1);
+                    for (String clusterName : clusters) {
+                        perClusterIndices.computeIfAbsent(clusterName, k -> new ArrayList<>()).add(indexName);
                     }
-                    indexName = index.substring(i + 1);
-                    clusterName = remoteClusterName;
+                } else {
+                    perClusterIndices.computeIfAbsent(LOCAL_CLUSTER_GROUP_KEY, k -> new ArrayList<>()).add(index);
                 }
+            } else {
+                perClusterIndices.computeIfAbsent(LOCAL_CLUSTER_GROUP_KEY, k -> new ArrayList<>()).add(index);
             }
-            perClusterIndices.computeIfAbsent(clusterName, k -> new ArrayList<String>()).add(indexName);
         }
         return perClusterIndices;
 }

core/src/main/java/org/elasticsearch/cluster/metadata/ClusterNameExpressionResolver.java

@@ -0,0 +1,100 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.cluster.metadata;
+
+import org.elasticsearch.common.component.AbstractComponent;
+import org.elasticsearch.common.regex.Regex;
+import org.elasticsearch.common.settings.Settings;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+/**
+ * Resolves cluster names from an expression. The expression must be the exact match of a cluster
+ * name or must be a wildcard expression.
+ */
+public final class ClusterNameExpressionResolver extends AbstractComponent {
+
+    private final WildcardExpressionResolver wildcardResolver = new WildcardExpressionResolver();
+
+    public ClusterNameExpressionResolver(Settings settings) {
+        super(settings);
+    }
+
+    /**
+     * Resolves the provided cluster expression to matching cluster names. This method only
+     * supports exact or wildcard matches.
+     *
+     * @param remoteClusters    the aliases for remote clusters
+     * @param clusterExpression the expressions that can be resolved to cluster names.
+     * @return the resolved cluster aliases.
+     */
+    public List<String> resolveClusterNames(Set<String> remoteClusters, String clusterExpression) {
+        if (remoteClusters.contains(clusterExpression)) {
+            return Collections.singletonList(clusterExpression);
+        } else if (Regex.isSimpleMatchPattern(clusterExpression)) {
+            return wildcardResolver.resolve(remoteClusters, clusterExpression);
+        } else {
+            return Collections.emptyList();
+        }
+    }
+
+    private static class WildcardExpressionResolver {
+
+        private List<String> resolve(Set<String> remoteClusters, String clusterExpression) {
+            if (isTrivialWildcard(clusterExpression)) {
+                return resolveTrivialWildcard(remoteClusters);
+            }
+
+            Set<String> matches = matches(remoteClusters, clusterExpression);
+            if (matches.isEmpty()) {
+                return Collections.emptyList();
+            } else {
+                return new ArrayList<>(matches);
+            }
+        }
+
+        private boolean isTrivialWildcard(String clusterExpression) {
+            return Regex.isMatchAllPattern(clusterExpression);
+        }
+
+        private List<String> resolveTrivialWildcard(Set<String> remoteClusters) {
+            return new ArrayList<>(remoteClusters);
+        }
+
+        private static Set<String> matches(Set<String> remoteClusters, String expression) {
+            if (expression.indexOf("*") == expression.length() - 1) {
+                return otherWildcard(remoteClusters, expression);
+            } else {
+                return otherWildcard(remoteClusters, expression);
+            }
+        }
+
+        private static Set<String> otherWildcard(Set<String> remoteClusters, String expression) {
+            final String pattern = expression;
+            return remoteClusters.stream()
+                .filter(n -> Regex.simpleMatch(pattern, n))
+                .collect(Collectors.toSet());
+        }
+    }
+}

core/src/test/java/org/elasticsearch/action/search/RemoteClusterServiceTests.java

@@ -143,14 +143,14 @@ public void testGroupClusterIndices() throws IOException {
                     assertTrue(service.isRemoteClusterRegistered("cluster_2"));
                     assertFalse(service.isRemoteClusterRegistered("foo"));
                     Map<String, List<String>> perClusterIndices = service.groupClusterIndices(new String[]{"foo:bar", "cluster_1:bar",
-                        "cluster_2:foo:bar", "cluster_1:test", "cluster_2:foo*", "foo"}, i -> false);
+                        "cluster_2:foo:bar", "cluster_1:test", "cluster_2:foo*", "foo", "cluster*:baz", "*:boo", "no*match:boo"}, i -> false);
                     String[] localIndices = perClusterIndices.computeIfAbsent(RemoteClusterService.LOCAL_CLUSTER_GROUP_KEY,
                         k -> Collections.emptyList()).toArray(new String[0]);
                     assertNotNull(perClusterIndices.remove(RemoteClusterService.LOCAL_CLUSTER_GROUP_KEY));
-                    assertArrayEquals(new String[]{"foo:bar", "foo"}, localIndices);
+                    assertArrayEquals(new String[]{"foo:bar", "foo", "no*match:boo"}, localIndices);
                     assertEquals(2, perClusterIndices.size());
-                    assertEquals(Arrays.asList("bar", "test"), perClusterIndices.get("cluster_1"));
-                    assertEquals(Arrays.asList("foo:bar", "foo*"), perClusterIndices.get("cluster_2"));
+                    assertEquals(Arrays.asList("bar", "test", "baz", "boo"), perClusterIndices.get("cluster_1"));
+                    assertEquals(Arrays.asList("foo:bar", "foo*", "baz", "boo"), perClusterIndices.get("cluster_2"));
 
                     IllegalArgumentException iae = expectThrows(IllegalArgumentException.class, () ->
                         service.groupClusterIndices(new String[]{"foo:bar", "cluster_1:bar",

core/src/test/java/org/elasticsearch/cluster/metadata/ClusterNameExpressionResolverTests.java

@@ -0,0 +1,75 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.cluster.metadata;
+
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.test.ESTestCase;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+public class ClusterNameExpressionResolverTests extends ESTestCase {
+
+    private ClusterNameExpressionResolver clusterNameResolver = new ClusterNameExpressionResolver(Settings.EMPTY);
+    private static final Set<String> remoteClusters = new HashSet<>();
+
+    static {
+        remoteClusters.add("cluster1");
+        remoteClusters.add("cluster2");
+        remoteClusters.add("totallyDifferent");
+    }
+
+    public void testExactMatch() {
+        List<String> clusters = clusterNameResolver.resolveClusterNames(remoteClusters, "totallyDifferent");
+        assertEquals(new HashSet<>(Arrays.asList("totallyDifferent")), new HashSet<>(clusters));
+    }
+
+    public void testNoWildCardNoMatch() {
+        List<String> clusters = clusterNameResolver.resolveClusterNames(remoteClusters, "totallyDifferent2");
+        assertNull(clusters);
+    }
+
+    public void testWildCardNoMatch() {
+        List<String> clusters = clusterNameResolver.resolveClusterNames(remoteClusters, "totally*2");
+        assertNull(clusters);
+    }
+
+    public void testSimpleWildCard() {
+        List<String> clusters = clusterNameResolver.resolveClusterNames(remoteClusters, "*");
+        assertEquals(new HashSet<>(Arrays.asList("cluster1", "cluster2", "totallyDifferent")), new HashSet<>(clusters));
+    }
+
+    public void testSuffixWildCard() {
+        List<String> clusters = clusterNameResolver.resolveClusterNames(remoteClusters, "cluster*");
+        assertEquals(new HashSet<>(Arrays.asList("cluster1", "cluster2")), new HashSet<>(clusters));
+    }
+
+    public void testPrefixWildCard() {
+        List<String> clusters = clusterNameResolver.resolveClusterNames(remoteClusters, "*Different");
+        assertEquals(new HashSet<>(Arrays.asList("totallyDifferent")), new HashSet<>(clusters));
+    }
+
+    public void testMiddleWildCard() {
+        List<String> clusters = clusterNameResolver.resolveClusterNames(remoteClusters, "clu*1");
+        assertEquals(new HashSet<>(Arrays.asList("cluster1")), new HashSet<>(clusters));
+    }
+}

qa/multi-cluster-search/src/test/resources/rest-api-spec/test/multi_cluster/10_basic.yaml

@@ -118,6 +118,30 @@
   - match: { hits.total: 6 }
   - match: { hits.hits.0._index: "test_remote_cluster:test_index" }
 
+---
+"Test wildcard search":
+  - do:
+      cluster.get_settings:
+        include_defaults: true
+
+  - set: { defaults.search.remote.my_remote_cluster.seeds.0: remote_ip }
+
+  - do:
+      cluster.put_settings:
+        flat_settings: true
+        body:
+          transient:
+            search.remote.test_remote_cluster.seeds: $remote_ip
+
+  - match: {transient: {search.remote.test_remote_cluster.seeds: $remote_ip}}
+
+  - do:
+      search:
+        index: "*:test_index"
+
+  - match: { _shards.total: 6 }
+  - match: { hits.total: 12 }
+
 ---
 "Search an filtered alias on the remote cluster":