When some shards are in unassigned state, it is useful to know the st…

…atuses of their copies in the cluster for shard recovery.

This PR adds an API that reports the nodes that hold copies of unassigned shards for specific indices, the shard versions
(which indicate how recent the copy is) and any exceptions encountered while trying to open the shard indices.
The action backing the API is implemented as a master read operation, reading the list of unassigned shards for specified
indicies from the cluster state and then fetching shard metadata from all the nodes in the cluster.

closes elastic#10952

core/src/main/java/org/elasticsearch/action/ActionModule.java

@@ -95,6 +95,8 @@
 import org.elasticsearch.action.admin.indices.recovery.TransportRecoveryAction;
 import org.elasticsearch.action.admin.indices.refresh.RefreshAction;
 import org.elasticsearch.action.admin.indices.refresh.TransportRefreshAction;
+import org.elasticsearch.action.admin.indices.shards.IndicesUnassignedShardsAction;
+import org.elasticsearch.action.admin.indices.shards.TransportIndicesUnassignedShardsAction;
 import org.elasticsearch.action.admin.indices.segments.IndicesSegmentsAction;
 import org.elasticsearch.action.admin.indices.segments.TransportIndicesSegmentsAction;
 import org.elasticsearch.action.admin.indices.settings.get.GetSettingsAction;
@@ -239,6 +241,7 @@ protected void configure() {
 
         registerAction(IndicesStatsAction.INSTANCE, TransportIndicesStatsAction.class);
         registerAction(IndicesSegmentsAction.INSTANCE, TransportIndicesSegmentsAction.class);
+        registerAction(IndicesUnassignedShardsAction.INSTANCE, TransportIndicesUnassignedShardsAction.class);
         registerAction(CreateIndexAction.INSTANCE, TransportCreateIndexAction.class);
         registerAction(DeleteIndexAction.INSTANCE, TransportDeleteIndexAction.class);
         registerAction(GetIndexAction.INSTANCE, TransportGetIndexAction.class);

core/src/main/java/org/elasticsearch/action/admin/indices/shards/IndicesUnassigedShardsRequestBuilder.java

@@ -0,0 +1,31 @@
+/*
+ * 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.action.admin.indices.shards;
+
+import org.elasticsearch.action.Action;
+import org.elasticsearch.action.support.master.MasterNodeReadOperationRequestBuilder;
+import org.elasticsearch.client.ElasticsearchClient;
+
+public class IndicesUnassigedShardsRequestBuilder extends MasterNodeReadOperationRequestBuilder<IndicesUnassignedShardsRequest, IndicesUnassigedShardsResponse, IndicesUnassigedShardsRequestBuilder> {
+
+    public IndicesUnassigedShardsRequestBuilder(ElasticsearchClient client, Action<IndicesUnassignedShardsRequest, IndicesUnassigedShardsResponse, IndicesUnassigedShardsRequestBuilder> action, String... indices) {
+        super(client, action, new IndicesUnassignedShardsRequest(indices));
+    }
+}

core/src/main/java/org/elasticsearch/action/admin/indices/shards/IndicesUnassigedShardsResponse.java

@@ -0,0 +1,166 @@
+/*
+ * 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.action.admin.indices.shards;
+
+import com.carrotsearch.hppc.cursors.ObjectObjectCursor;
+import org.elasticsearch.action.ActionResponse;
+import org.elasticsearch.common.collect.ImmutableOpenMap;
+import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.common.xcontent.ToXContent;
+import org.elasticsearch.common.xcontent.XContentBuilder;
+import org.elasticsearch.common.xcontent.XContentBuilderString;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class IndicesUnassigedShardsResponse extends ActionResponse implements ToXContent {
+
+    public static class ShardStatus {
+
+        /**
+         * Id of the node the shard belongs to
+         */
+        public final String nodeID;
+
+        /**
+         * Version of the shard, the highest
+         * version of the replica shards are
+         * promoted to primary if needed
+         */
+        public final long version;
+
+        /**
+         * Any exception that occurred
+         * while trying to open the
+         * shard index
+         */
+        public final String exception;
+
+        ShardStatus(String nodeID, long version, String exception) {
+            this.nodeID = nodeID;
+            this.version = version;
+            this.exception = exception;
+        }
+    }
+
+    private ImmutableOpenMap<String, Map<Integer, List<ShardStatus>>> shardStatuses = ImmutableOpenMap.of();
+
+    public IndicesUnassigedShardsResponse(ImmutableOpenMap<String, Map<Integer, List<ShardStatus>>> shardStatuses) {
+        this.shardStatuses = shardStatuses;
+    }
+
+    IndicesUnassigedShardsResponse() {
+    }
+
+    /**
+     * Returns {@link org.elasticsearch.action.admin.indices.shards.IndicesUnassigedShardsResponse.ShardStatus}s
+     * grouped by their index names and shard ids.
+     */
+    public ImmutableOpenMap<String, Map<Integer, List<ShardStatus>>> getShardStatuses() {
+        return shardStatuses;
+    }
+
+    @Override
+    public void readFrom(StreamInput in) throws IOException {
+        super.readFrom(in);
+        int size = in.readVInt();
+        ImmutableOpenMap.Builder<String, Map<Integer, List<ShardStatus>>> replicaMetaDataBuilder = ImmutableOpenMap.builder();
+        for (int i = 0; i < size; i++) {
+            String index = in.readString();
+            int indexEntries = in.readVInt();
+            Map<Integer, List<ShardStatus>> shardEntries = new HashMap<>(indexEntries);
+            for (int shardCount = 0; shardCount < indexEntries; shardCount++) {
+                int shardID = in.readInt();
+                int nodeEntries = in.readVInt();
+                List<ShardStatus> dataList = new ArrayList<>(nodeEntries);
+                for (int nodeCount = 0; nodeCount < nodeEntries; nodeCount++) {
+                    String nodeID = in.readString();
+                    long version = in.readLong();
+                    String exception = in.readOptionalString();
+                    dataList.add(new ShardStatus(nodeID, version, exception));
+                }
+                shardEntries.put(shardID, dataList);
+            }
+            replicaMetaDataBuilder.put(index, shardEntries);
+        }
+        shardStatuses = replicaMetaDataBuilder.build();
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        super.writeTo(out);
+        out.writeVInt(shardStatuses.size());
+        for (ObjectObjectCursor<String, Map<Integer, List<ShardStatus>>> cursor : shardStatuses) {
+            out.writeString(cursor.key);
+            out.writeVInt(cursor.value.size());
+            for (Map.Entry<Integer, List<ShardStatus>> listEntry : cursor.value.entrySet()) {
+                out.writeInt(listEntry.getKey());
+                out.writeVInt(listEntry.getValue().size());
+                for (ShardStatus data : listEntry.getValue()) {
+                    out.writeString(data.nodeID);
+                    out.writeLong(data.version);
+                    out.writeOptionalString(data.exception);
+                }
+            }
+        }
+    }
+
+    @Override
+    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+        builder.startObject(Fields.INDICES);
+        for (ObjectObjectCursor<String, Map<Integer, List<ShardStatus>>> cursor : shardStatuses) {
+            builder.startObject(cursor.key);
+
+            builder.startObject(Fields.SHARDS);
+            for (Map.Entry<Integer, List<ShardStatus>> listEntry : cursor.value.entrySet()) {
+                builder.startArray(String.valueOf(listEntry.getKey()));
+
+                for (ShardStatus metaData : listEntry.getValue()) {
+                    builder.startObject();
+                    builder.field(Fields.NODE, metaData.nodeID);
+                    builder.field(Fields.VERSION, metaData.version);
+                    if (metaData.exception != null) {
+                        builder.field(Fields.EXCEPTION, metaData.exception);
+                    }
+                    builder.endObject();
+                }
+
+                builder.endArray();
+            }
+            builder.endObject();
+
+            builder.endObject();
+        }
+        builder.endObject();
+        return builder;
+    }
+
+    static final class Fields {
+        static final XContentBuilderString INDICES = new XContentBuilderString("indices");
+        static final XContentBuilderString SHARDS = new XContentBuilderString("shards");
+        static final XContentBuilderString NODE = new XContentBuilderString("node");
+        static final XContentBuilderString VERSION = new XContentBuilderString("version");
+        static final XContentBuilderString EXCEPTION = new XContentBuilderString("exception");
+    }
+}

core/src/main/java/org/elasticsearch/action/admin/indices/shards/IndicesUnassignedShardsAction.java

@@ -0,0 +1,49 @@
+/*
+ * 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.action.admin.indices.shards;
+
+import org.elasticsearch.action.Action;
+import org.elasticsearch.client.ElasticsearchClient;
+
+/**
+ * Action for {@link TransportIndicesUnassignedShardsAction}
+ *
+ * Exposes information about where unassigned shards are located, how recent they are
+ * and reports if the shards can be opened
+ */
+public class IndicesUnassignedShardsAction extends Action<IndicesUnassignedShardsRequest, IndicesUnassigedShardsResponse, IndicesUnassigedShardsRequestBuilder> {
+
+    public static final IndicesUnassignedShardsAction INSTANCE = new IndicesUnassignedShardsAction();
+    public static final String NAME = "indices:monitor/unassigned_shards";
+
+    private IndicesUnassignedShardsAction() {
+        super(NAME);
+    }
+
+    @Override
+    public IndicesUnassigedShardsResponse newResponse() {
+        return new IndicesUnassigedShardsResponse();
+    }
+
+    @Override
+    public IndicesUnassigedShardsRequestBuilder newRequestBuilder(ElasticsearchClient client) {
+        return new IndicesUnassigedShardsRequestBuilder(client, this);
+    }
+}

core/src/main/java/org/elasticsearch/action/admin/indices/shards/IndicesUnassignedShardsRequest.java

@@ -0,0 +1,88 @@
+/*
+ * 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.action.admin.indices.shards;
+
+import org.elasticsearch.action.ActionRequestValidationException;
+import org.elasticsearch.action.IndicesRequest;
+import org.elasticsearch.action.support.IndicesOptions;
+import org.elasticsearch.action.support.master.MasterNodeReadRequest;
+import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.common.io.stream.StreamOutput;
+
+import java.io.IOException;
+
+public class IndicesUnassignedShardsRequest extends MasterNodeReadRequest<IndicesUnassignedShardsRequest> implements IndicesRequest.Replaceable {
+
+    private String[] indices = Strings.EMPTY_ARRAY;
+    private IndicesOptions indicesOptions = IndicesOptions.strictExpandOpenAndForbidClosed();
+
+    /**
+     * Create a request for unassigned shards info for <code>indices</code>
+     */
+    public IndicesUnassignedShardsRequest(String... indices) {
+        this.indices = indices;
+    }
+
+    public IndicesUnassignedShardsRequest(String index) {
+        this.indices = new String[]{index};
+    }
+
+    public IndicesUnassignedShardsRequest() {
+    }
+
+    @Override
+    public String[] indices() {
+        return indices;
+    }
+
+    @Override
+    public IndicesOptions indicesOptions() {
+        return indicesOptions;
+    }
+
+    public void indicesOptions(IndicesOptions indicesOptions) {
+        this.indicesOptions = indicesOptions;
+    }
+
+    @Override
+    public IndicesUnassignedShardsRequest indices(String... indices) {
+        this.indices = indices;
+        return this;
+    }
+
+    @Override
+    public ActionRequestValidationException validate() {
+        return null;
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        super.writeTo(out);
+        out.writeStringArrayNullable(indices);
+        indicesOptions.writeIndicesOptions(out);
+    }
+
+    @Override
+    public void readFrom(StreamInput in) throws IOException {
+        super.readFrom(in);
+        indices = in.readStringArray();
+        indicesOptions = IndicesOptions.readIndicesOptions(in);
+    }
+}