Add GET api to get weighted round robin shard routing weights

Signed-off-by: Anshu Agarwal <anshukag@amazon.com>

rest-api-spec/src/main/resources/rest-api-spec/api/cluster.get_wrr_weights.json

@@ -0,0 +1,25 @@
+{
+  "cluster.get_wrr_weights": {
+    "documentation": {
+      "url": "TBA",
+      "description": "TBA"
+    },
+    "stability": "experimental",
+    "url": {
+      "paths": [
+        {
+          "path": "/_cluster/routing/awareness/{attribute}/weights",
+          "methods": [
+            "GET"
+          ],
+          "parts": {
+            "attribute": {
+              "type": "string",
+              "description": "Awareness attribute name"
+            }
+          }
+        }
+      ]
+    }
+  }
+}

server/src/internalClusterTest/java/org/opensearch/cluster/routing/WRRRoutingIT.java

@@ -0,0 +1,50 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.cluster.routing;
+
+import org.opensearch.action.ActionRequestValidationException;
+import org.opensearch.action.admin.cluster.shards.routing.wrr.get.ClusterGetWRRWeightsResponse;
+import org.opensearch.action.admin.cluster.shards.routing.wrr.put.ClusterPutWRRWeightsResponse;
+
+import org.opensearch.test.OpenSearchIntegTestCase;
+
+import java.util.Map;
+
+import static org.opensearch.test.OpenSearchIntegTestCase.Scope.TEST;
+
+@OpenSearchIntegTestCase.ClusterScope(scope = TEST, supportsDedicatedMasters = true, numDataNodes = 3)
+public class WRRRoutingIT extends OpenSearchIntegTestCase {
+
+    public void testUpdateWRRWeights() {
+
+        Map<String, Object> weights = Map.of("a", "1", "b", "1", "c", "0");
+        WRRWeight wrrWeight = new WRRWeight("zone", weights);
+        ClusterPutWRRWeightsResponse response = client().admin().cluster().prepareWRRWeights().setWRRWeights(wrrWeight).get();
+        assertEquals(response.isAcknowledged(), true);
+    }
+
+    public void testUpdateWRRWeights_MoreThanOneZoneHasZeroWeight() {
+
+        Map<String, Object> weights = Map.of("a", "1", "b", "0", "c", "0");
+        WRRWeight wrrWeight = new WRRWeight("zone", weights);
+        assertThrows(
+            ActionRequestValidationException.class,
+            () -> client().admin().cluster().prepareWRRWeights().setWRRWeights(wrrWeight).get()
+        );
+    }
+
+    public void testGetWRRWeights() {
+
+        Map<String, Object> weights = Map.of("a", "1", "b", "1", "c", "1");
+        WRRWeight wrrWeight = new WRRWeight("zone", weights);
+        ClusterPutWRRWeightsResponse response = client().admin().cluster().prepareWRRWeights().setWRRWeights(wrrWeight).get();
+        ClusterGetWRRWeightsResponse response1 = client().admin().cluster().prepareGetWRRWeights().get();
+        assertEquals(response1.weights(), wrrWeight);
+    }
+}

server/src/main/java/org/opensearch/action/ActionModule.java

@@ -79,7 +79,9 @@
 import org.opensearch.action.admin.cluster.settings.TransportClusterUpdateSettingsAction;
 import org.opensearch.action.admin.cluster.shards.ClusterSearchShardsAction;
 import org.opensearch.action.admin.cluster.shards.TransportClusterSearchShardsAction;
+import org.opensearch.action.admin.cluster.shards.routing.wrr.get.ClusterGetWRRWeightsAction;
 import org.opensearch.action.admin.cluster.shards.routing.wrr.put.ClusterPutWRRWeightsAction;
+import org.opensearch.action.admin.cluster.shards.routing.wrr.get.TransportGetWRRWeightsAction;
 import org.opensearch.action.admin.cluster.shards.routing.wrr.put.TransportPutWRRWeightsAction;
 import org.opensearch.action.admin.cluster.snapshots.clone.CloneSnapshotAction;
 import org.opensearch.action.admin.cluster.snapshots.clone.TransportCloneSnapshotAction;
@@ -293,6 +295,7 @@
 import org.opensearch.rest.action.admin.cluster.RestCloneSnapshotAction;
 import org.opensearch.rest.action.admin.cluster.RestClusterAllocationExplainAction;
 import org.opensearch.rest.action.admin.cluster.RestClusterGetSettingsAction;
+import org.opensearch.rest.action.admin.cluster.RestClusterGetWRRWeightsAction;
 import org.opensearch.rest.action.admin.cluster.RestClusterHealthAction;
 import org.opensearch.rest.action.admin.cluster.RestClusterPutWRRWeightsAction;
 import org.opensearch.rest.action.admin.cluster.RestClusterRerouteAction;
@@ -561,6 +564,7 @@ public <Request extends ActionRequest, Response extends ActionResponse> void reg
         actions.register(RestoreSnapshotAction.INSTANCE, TransportRestoreSnapshotAction.class);
         actions.register(SnapshotsStatusAction.INSTANCE, TransportSnapshotsStatusAction.class);
         actions.register(ClusterPutWRRWeightsAction.INSTANCE, TransportPutWRRWeightsAction.class);
+        actions.register(ClusterGetWRRWeightsAction.INSTANCE, TransportGetWRRWeightsAction.class);
         actions.register(IndicesStatsAction.INSTANCE, TransportIndicesStatsAction.class);
         actions.register(IndicesSegmentsAction.INSTANCE, TransportIndicesSegmentsAction.class);
         actions.register(IndicesShardStoresAction.INSTANCE, TransportIndicesShardStoresAction.class);
@@ -742,6 +746,7 @@ public void initRestHandlers(Supplier<DiscoveryNodes> nodesInCluster) {
         registerHandler.accept(new RestOpenIndexAction());
         registerHandler.accept(new RestAddIndexBlockAction());
         registerHandler.accept(new RestClusterPutWRRWeightsAction());
+        registerHandler.accept(new RestClusterGetWRRWeightsAction());
 
         registerHandler.accept(new RestUpdateSettingsAction());
         registerHandler.accept(new RestGetSettingsAction());

server/src/main/java/org/opensearch/action/admin/cluster/shards/routing/wrr/get/ClusterGetWRRWeightsAction.java

@@ -0,0 +1,25 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.action.admin.cluster.shards.routing.wrr.get;
+
+import org.opensearch.action.ActionType;
+
+/**
+ * Action to get weights for weighted round-robin search routing policy.
+ *
+ * @opensearch.internal
+ */
+public class ClusterGetWRRWeightsAction extends ActionType<ClusterGetWRRWeightsResponse> {
+    public static final ClusterGetWRRWeightsAction INSTANCE = new ClusterGetWRRWeightsAction();
+    public static final String NAME = "cluster:admin/routing/awareness/weights/get";
+
+    private ClusterGetWRRWeightsAction() {
+        super(NAME, ClusterGetWRRWeightsResponse::new);
+    }
+}

server/src/main/java/org/opensearch/action/admin/cluster/shards/routing/wrr/get/ClusterGetWRRWeightsRequest.java

@@ -0,0 +1,57 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.action.admin.cluster.shards.routing.wrr.get;
+
+import org.opensearch.action.ActionRequestValidationException;
+import org.opensearch.action.support.clustermanager.ClusterManagerNodeReadRequest;
+import org.opensearch.cluster.routing.WRRWeight;
+import org.opensearch.common.io.stream.StreamInput;
+import org.opensearch.common.io.stream.StreamOutput;
+
+import java.io.IOException;
+import java.util.List;
+
+/**
+ * Request to get weights for weighted round-robin search routing policy.
+ *
+ * @opensearch.internal
+ */
+public class ClusterGetWRRWeightsRequest extends ClusterManagerNodeReadRequest<ClusterGetWRRWeightsRequest> {
+    String awarenessAttribute;
+
+    public String getAwarenessAttribute() {
+        return awarenessAttribute;
+    }
+
+    public void setAwarenessAttribute(String awarenessAttribute) {
+        this.awarenessAttribute = awarenessAttribute;
+    }
+
+    public ClusterGetWRRWeightsRequest() {
+    }
+
+    public ClusterGetWRRWeightsRequest(StreamInput in) throws IOException {
+        super(in);
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        super.writeTo(out);
+    }
+
+    @Override
+    public ActionRequestValidationException validate() {
+        return null;
+    }
+
+    public ClusterGetWRRWeightsRequest weights(List<WRRWeight> weights) {
+        return this;
+    }
+
+}

server/src/main/java/org/opensearch/action/admin/cluster/shards/routing/wrr/get/ClusterGetWRRWeightsRequestBuilder.java

@@ -0,0 +1,36 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.action.admin.cluster.shards.routing.wrr.get;
+
+import org.opensearch.action.support.clustermanager.ClusterManagerNodeReadOperationRequestBuilder;
+import org.opensearch.client.OpenSearchClient;
+import org.opensearch.cluster.routing.WRRWeight;
+
+import java.util.List;
+
+/**
+ * Request builder to get weights for weighted round-robin search routing policy.
+ *
+ * @opensearch.internal
+ */
+public class ClusterGetWRRWeightsRequestBuilder extends ClusterManagerNodeReadOperationRequestBuilder<
+    ClusterGetWRRWeightsRequest,
+    ClusterGetWRRWeightsResponse,
+    ClusterGetWRRWeightsRequestBuilder> {
+
+    public ClusterGetWRRWeightsRequestBuilder(OpenSearchClient client, ClusterGetWRRWeightsAction action) {
+        super(client, action, new ClusterGetWRRWeightsRequest());
+    }
+
+    public ClusterGetWRRWeightsRequestBuilder setWeights(List<WRRWeight> weights) {
+        request.weights(weights);
+        return this;
+    }
+
+}

server/src/main/java/org/opensearch/action/admin/cluster/shards/routing/wrr/get/ClusterGetWRRWeightsResponse.java

@@ -0,0 +1,103 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.action.admin.cluster.shards.routing.wrr.get;
+
+import org.opensearch.action.ActionResponse;
+
+import org.opensearch.cluster.metadata.WeightedRoundRobinMetadata;
+import org.opensearch.cluster.routing.WRRWeight;
+import org.opensearch.common.io.stream.StreamInput;
+import org.opensearch.common.io.stream.StreamOutput;
+import org.opensearch.common.xcontent.ToXContentObject;
+import org.opensearch.common.xcontent.XContentBuilder;
+import org.opensearch.common.xcontent.XContentParser;
+
+import java.io.IOException;
+import java.util.Map;
+
+import static org.opensearch.common.xcontent.XContentParserUtils.ensureExpectedToken;
+
+/**
+ * Response from fetching weights for weighted round-robin search routing policy.
+ *
+ * @opensearch.internal
+ */
+public class ClusterGetWRRWeightsResponse extends ActionResponse implements ToXContentObject {
+    private WRRWeight wrrWeight;
+    private Object localNodeWeight;
+
+    ClusterGetWRRWeightsResponse() {
+        this.wrrWeight = null;
+    }
+
+    ClusterGetWRRWeightsResponse(Object localNodeWeight, WRRWeight wrrWeight) {
+        this.localNodeWeight = localNodeWeight;
+        this.wrrWeight = wrrWeight;
+
+    }
+
+    ClusterGetWRRWeightsResponse(WRRWeight wrrWeights) {
+        this.wrrWeight = wrrWeights;
+    }
+
+    ClusterGetWRRWeightsResponse(WeightedRoundRobinMetadata metadata) {
+
+        this.wrrWeight = metadata.getWrrWeight();
+    }
+
+    ClusterGetWRRWeightsResponse(StreamInput in) throws IOException {
+        if (in.available() != 0) {
+            this.wrrWeight = new WRRWeight(in);
+
+        }
+    }
+
+    /**
+     * List of weights to return
+     *
+     * @return list or weights
+     */
+    public WRRWeight weights() {
+        return this.wrrWeight;
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        if (wrrWeight != null) {
+            wrrWeight.writeTo(out);
+
+        }
+    }
+
+    @Override
+    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+        builder.startObject();
+        if (this.wrrWeight != null) {
+            for (Map.Entry<String, Object> entry : wrrWeight.weights().entrySet()) {
+                builder.field(entry.getKey(), entry.getValue());
+            }
+            if (localNodeWeight != null) {
+                builder.field("node_weight", localNodeWeight.toString());
+            }
+        } else if (localNodeWeight != null) {
+            builder.field("node_weight", localNodeWeight.toString());
+        } else {
+            builder.field("msg", "Weights are not set");
+        }
+
+        builder.endObject();
+
+        return builder;
+    }
+
+    public static ClusterGetWRRWeightsResponse fromXContent(XContentParser parser) throws IOException {
+        ensureExpectedToken(XContentParser.Token.START_OBJECT, parser.nextToken(), parser);
+        return new ClusterGetWRRWeightsResponse(WeightedRoundRobinMetadata.fromXContent(parser));
+    }
+}