Add a deprecation warning regarding allocation awareness in search request (#48351)

This is a follow up of #43453 where we added
a system property to disallow allocation awareness in search requests. Since search requests
will no longer check the allocation awareness attributes for routing in the next major version,
this change adds a deprecation warning on any setup that uses these attributes.

Relates #43453

Author: jimczi

qa/evil-tests/src/test/java/org/elasticsearch/cluster/routing/EvilSystemPropertyTests.java

@@ -34,6 +34,7 @@ public void testDisableSearchAllocationAwareness() {
             .build();
         OperationRouting routing = new OperationRouting(indexSettings,
             new ClusterSettings(Settings.EMPTY, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS));
+        assertWarnings(OperationRouting.IGNORE_AWARENESS_ATTRIBUTES_DEPRECATION_MESSAGE);
         assertThat(routing.getAwarenessAttributes().size(), equalTo(1));
         assertThat(routing.getAwarenessAttributes().get(0), equalTo("test"));
         System.setProperty("es.search.ignore_awareness_attributes", "true");

server/src/main/java/org/elasticsearch/cluster/routing/OperationRouting.java

@@ -19,13 +19,15 @@
 
 package org.elasticsearch.cluster.routing;
 
+import org.apache.logging.log4j.LogManager;
 import org.elasticsearch.Version;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.metadata.IndexMetaData;
 import org.elasticsearch.cluster.node.DiscoveryNodes;
 import org.elasticsearch.cluster.routing.allocation.decider.AwarenessAllocationDecider;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.common.settings.ClusterSettings;
 import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.common.settings.Settings;
@@ -50,14 +52,23 @@ public class OperationRouting {
             Setting.boolSetting("cluster.routing.use_adaptive_replica_selection", true,
                     Setting.Property.Dynamic, Setting.Property.NodeScope);
 
+    private static final DeprecationLogger deprecationLogger = new DeprecationLogger(LogManager.getLogger(OperationRouting.class));
+    private static final String IGNORE_AWARENESS_ATTRIBUTES_PROPERTY = "es.search.ignore_awareness_attributes";
+    static final String IGNORE_AWARENESS_ATTRIBUTES_DEPRECATION_MESSAGE =
+        "searches will not be routed based on awareness attributes starting in version 8.0.0; " +
+            "to opt into this behaviour now please set the system property [" + IGNORE_AWARENESS_ATTRIBUTES_PROPERTY + "] to [true]";
+
     private List<String> awarenessAttributes;
     private boolean useAdaptiveReplicaSelection;
 
     public OperationRouting(Settings settings, ClusterSettings clusterSettings) {
         // whether to ignore awareness attributes when routing requests
-        boolean ignoreAwarenessAttr = parseBoolean(System.getProperty("es.search.ignore_awareness_attributes"), false);
+        boolean ignoreAwarenessAttr = parseBoolean(System.getProperty(IGNORE_AWARENESS_ATTRIBUTES_PROPERTY), false);
         if (ignoreAwarenessAttr == false) {
             awarenessAttributes = AwarenessAllocationDecider.CLUSTER_ROUTING_ALLOCATION_AWARENESS_ATTRIBUTE_SETTING.get(settings);
+            if (awarenessAttributes.isEmpty() == false) {
+                deprecationLogger.deprecated(IGNORE_AWARENESS_ATTRIBUTES_DEPRECATION_MESSAGE);
+            }
             clusterSettings.addSettingsUpdateConsumer(AwarenessAllocationDecider.CLUSTER_ROUTING_ALLOCATION_AWARENESS_ATTRIBUTE_SETTING,
                 this::setAwarenessAttributes);
         } else {
@@ -77,7 +88,13 @@ List<String> getAwarenessAttributes() {
     }
 
     private void setAwarenessAttributes(List<String> awarenessAttributes) {
-        this.awarenessAttributes = awarenessAttributes;
+        boolean ignoreAwarenessAttr = parseBoolean(System.getProperty(IGNORE_AWARENESS_ATTRIBUTES_PROPERTY), false);
+        if (ignoreAwarenessAttr == false) {
+            if (this.awarenessAttributes.isEmpty() && awarenessAttributes.isEmpty() == false) {
+                deprecationLogger.deprecated(IGNORE_AWARENESS_ATTRIBUTES_DEPRECATION_MESSAGE);
+            }
+            this.awarenessAttributes = awarenessAttributes;
+        }
     }
 
     public ShardIterator indexShards(ClusterState clusterState, String index, String id, @Nullable String routing) {

server/src/test/java/org/elasticsearch/cluster/routing/OperationRoutingTests.java

@@ -22,6 +22,7 @@
 import org.elasticsearch.action.support.replication.ClusterStateCreationUtils;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.metadata.IndexMetaData;
+import org.elasticsearch.cluster.routing.allocation.decider.AwarenessAllocationDecider;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.settings.ClusterSettings;
 import org.elasticsearch.common.settings.Settings;
@@ -44,14 +45,14 @@
 import java.util.Set;
 import java.util.TreeMap;
 
+import static org.elasticsearch.cluster.routing.OperationRouting.IGNORE_AWARENESS_ATTRIBUTES_DEPRECATION_MESSAGE;
 import static org.hamcrest.CoreMatchers.containsString;
 import static org.hamcrest.Matchers.containsInAnyOrder;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.greaterThan;
 import static org.hamcrest.object.HasToString.hasToString;
 
-public class OperationRoutingTests extends ESTestCase{
-
+public class OperationRoutingTests extends ESTestCase {
     public void testGenerateShardId() {
         int[][] possibleValues = new int[][] {
             {8,4,2}, {20, 10, 2}, {36, 12, 3}, {15,5,1}
@@ -606,4 +607,14 @@ public void testAdaptiveReplicaSelection() throws Exception {
         terminate(threadPool);
     }
 
+    public void testAllocationAwarenessDeprecation() {
+        OperationRouting routing = new OperationRouting(
+            Settings.builder()
+                .put(AwarenessAllocationDecider.CLUSTER_ROUTING_ALLOCATION_AWARENESS_ATTRIBUTE_SETTING.getKey(), "foo")
+                .build(),
+            new ClusterSettings(Settings.EMPTY, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS)
+        );
+        assertWarnings(IGNORE_AWARENESS_ATTRIBUTES_DEPRECATION_MESSAGE);
+    }
+
 }