Update Rest status for DecommissioningFailedException (#5283)

Signed-off-by: Rishab Nahata <rnnahata@amazon.com>

CHANGELOG.md

@@ -25,6 +25,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Bumps `proto-google-common-protos` from 2.8.0 to 2.10.0 ([#5318](https://github.com/opensearch-project/OpenSearch/pull/5318))
 - Bumps `protobuf-java` from 3.21.7 to 3.21.9 ([#5319](https://github.com/opensearch-project/OpenSearch/pull/5319))
 ### Changed
+- Change http code for DecommissioningFailedException from 500 to 400 ([#5283](https://github.com/opensearch-project/OpenSearch/pull/5283))
+
 ### Deprecated
 ### Removed
 ### Fixed

qa/smoke-test-http/src/test/java/org/opensearch/http/AwarenessAttributeDecommissionRestIT.java

@@ -0,0 +1,101 @@
+/*
+ * 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.http;
+
+import org.opensearch.action.admin.cluster.shards.routing.weighted.put.ClusterPutWeightedRoutingResponse;
+import org.opensearch.client.Request;
+import org.opensearch.client.Response;
+import org.opensearch.client.ResponseException;
+import org.opensearch.cluster.node.DiscoveryNodeRole;
+import org.opensearch.cluster.routing.WeightedRouting;
+import org.opensearch.common.settings.Settings;
+import org.opensearch.rest.RestStatus;
+import org.opensearch.test.OpenSearchIntegTestCase;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+
+import static org.opensearch.test.NodeRoles.onlyRole;
+
+@OpenSearchIntegTestCase.ClusterScope(scope = OpenSearchIntegTestCase.Scope.TEST, numDataNodes = 0)
+public class AwarenessAttributeDecommissionRestIT extends HttpSmokeTestCase{
+
+    public void testRestStatusForDecommissioningFailedException() {
+        internalCluster().startNodes(3);
+        Request request = new Request("PUT", "/_cluster/decommission/awareness/zone/zone-1");
+        ResponseException exception = expectThrows(
+            ResponseException.class,
+            () -> getRestClient().performRequest(request)
+        );
+        assertEquals(exception.getResponse().getStatusLine().getStatusCode(), RestStatus.BAD_REQUEST.getStatus());
+        assertTrue(exception.getMessage().contains("invalid awareness attribute requested for decommissioning"));
+    }
+
+    public void testRestStatusForAcknowledgedDecommission() throws IOException {
+        Settings commonSettings = Settings.builder()
+            .put("cluster.routing.allocation.awareness.attributes", "zone")
+            .put("cluster.routing.allocation.awareness.force.zone.values", "a,b,c")
+            .build();
+
+        logger.info("--> start 3 cluster manager nodes on zones 'a' & 'b' & 'c'");
+        List<String> clusterManagerNodes = internalCluster().startNodes(
+            Settings.builder()
+                .put(commonSettings)
+                .put("node.attr.zone", "a")
+                .put(onlyRole(commonSettings, DiscoveryNodeRole.CLUSTER_MANAGER_ROLE))
+                .build(),
+            Settings.builder()
+                .put(commonSettings)
+                .put("node.attr.zone", "b")
+                .put(onlyRole(commonSettings, DiscoveryNodeRole.CLUSTER_MANAGER_ROLE))
+                .build(),
+            Settings.builder()
+                .put(commonSettings)
+                .put("node.attr.zone", "c")
+                .put(onlyRole(commonSettings, DiscoveryNodeRole.CLUSTER_MANAGER_ROLE))
+                .build()
+        );
+
+        logger.info("--> start 3 data nodes on zones 'a' & 'b' & 'c'");
+        List<String> dataNodes = internalCluster().startNodes(
+            Settings.builder()
+                .put(commonSettings)
+                .put("node.attr.zone", "a")
+                .put(onlyRole(commonSettings, DiscoveryNodeRole.DATA_ROLE))
+                .build(),
+            Settings.builder()
+                .put(commonSettings)
+                .put("node.attr.zone", "b")
+                .put(onlyRole(commonSettings, DiscoveryNodeRole.DATA_ROLE))
+                .build(),
+            Settings.builder()
+                .put(commonSettings)
+                .put("node.attr.zone", "c")
+                .put(onlyRole(commonSettings, DiscoveryNodeRole.DATA_ROLE))
+                .build()
+        );
+
+        ensureStableCluster(6);
+        logger.info("--> setting shard routing weights for weighted round robin");
+        Map<String, Double> weights = Map.of("a", 1.0, "b", 1.0, "c", 0.0);
+        WeightedRouting weightedRouting = new WeightedRouting("zone", weights);
+
+        ClusterPutWeightedRoutingResponse weightedRoutingResponse = client().admin()
+            .cluster()
+            .prepareWeightedRouting()
+            .setWeightedRouting(weightedRouting)
+            .get();
+        assertTrue(weightedRoutingResponse.isAcknowledged());
+
+        Request request = new Request("PUT", "/_cluster/decommission/awareness/zone/c");
+        Response response = getRestClient().performRequest(request);
+        assertEquals(response.getStatusLine().getStatusCode(), RestStatus.OK.getStatus());
+    }
+}

server/src/main/java/org/opensearch/cluster/decommission/DecommissioningFailedException.java

@@ -11,6 +11,7 @@
 import org.opensearch.OpenSearchException;
 import org.opensearch.common.io.stream.StreamInput;
 import org.opensearch.common.io.stream.StreamOutput;
+import org.opensearch.rest.RestStatus;
 
 import java.io.IOException;
 
@@ -52,4 +53,9 @@ public void writeTo(StreamOutput out) throws IOException {
     public DecommissionAttribute decommissionAttribute() {
         return decommissionAttribute;
     }
+
+    @Override
+    public RestStatus status() {
+        return RestStatus.BAD_REQUEST;
+    }
 }