Relax SearchReplicaAllocation decider

It doesn't make sense to require that search replicas be allocated to
nodes with the search role if the cluster has no nodes with the search
role.

Signed-off-by: Michael Froh <[email protected]>

Author: msfroh

server/src/main/java/org/opensearch/cluster/metadata/MetadataCreateIndexService.java

@@ -1179,8 +1179,7 @@ public static void updateRemoteStoreSettings(
                 translogRepo = RemoteStoreNodeAttribute.getTranslogRepoName(remoteNode.get().getAttributes());
                 segmentRepo = RemoteStoreNodeAttribute.getSegmentRepoName(remoteNode.get().getAttributes());
                 if (segmentRepo != null) {
-                    settingsBuilder.put(SETTING_REMOTE_STORE_ENABLED, true)
-                        .put(SETTING_REMOTE_SEGMENT_STORE_REPOSITORY, segmentRepo);
+                    settingsBuilder.put(SETTING_REMOTE_STORE_ENABLED, true).put(SETTING_REMOTE_SEGMENT_STORE_REPOSITORY, segmentRepo);
                     if (translogRepo != null) {
                         settingsBuilder.put(SETTING_REMOTE_TRANSLOG_STORE_REPOSITORY, translogRepo);
                     }

server/src/main/java/org/opensearch/cluster/routing/allocation/decider/SearchReplicaAllocationDecider.java

@@ -34,8 +34,15 @@ public Decision canRemain(ShardRouting shardRouting, RoutingNode node, RoutingAl
 
     private Decision canAllocate(ShardRouting shardRouting, DiscoveryNode node, RoutingAllocation allocation) {
         boolean isSearchReplica = shardRouting.isSearchOnly();
+        boolean existSearchNodes = false;
+        for (DiscoveryNode discoveryNode : allocation.nodes()) {
+            if (discoveryNode.isSearchNode()) {
+                existSearchNodes = true;
+            }
+        }
+        boolean canAllocateSearchReplica = node.isSearchNode() || (existSearchNodes == false);
 
-        if ((node.isSearchNode() && isSearchReplica) || (node.isSearchNode() == false && isSearchReplica == false)) {
+        if ((canAllocateSearchReplica && isSearchReplica) || (node.isSearchNode() == false && isSearchReplica == false)) {
             return allocation.decision(
                 Decision.YES,
                 NAME,

server/src/main/java/org/opensearch/indices/IndicesService.java

@@ -216,7 +216,6 @@
 import static org.opensearch.index.TieredMergePolicyProvider.MIN_DEFAULT_MAX_MERGE_AT_ONCE;
 import static org.opensearch.index.query.AbstractQueryBuilder.parseInnerQueryBuilder;
 import static org.opensearch.indices.IndicesRequestCache.INDICES_REQUEST_CACHE_MAX_SIZE_ALLOWED_IN_CACHE_SETTING;
-import static org.opensearch.node.remotestore.RemoteStoreNodeAttribute.isRemoteDataAttributePresent;
 import static org.opensearch.search.SearchService.ALLOW_EXPENSIVE_QUERIES;
 
 /**

server/src/main/java/org/opensearch/node/remotestore/RemoteStoreNodeAttribute.java

@@ -194,17 +194,17 @@ private static Tuple<String, String> getValue(Map<String, String> attributes, Li
 
     private Map<String, String> getValidatedRepositoryNames(DiscoveryNode node) {
         Set<Tuple<String, String>> repositoryNames = new HashSet<>();
-        if (containsKey(node.getAttributes(), REMOTE_SEGMENT_REPOSITORY_NAME_ATTRIBUTE_KEYS) &&
-            containsKey(node.getAttributes(), List.of(REMOTE_STORE_SEGMENTS_ONLY_ATTRIBUTE_KEY)) &&
-            "true".equals(node.getAttributes().get(REMOTE_STORE_SEGMENTS_ONLY_ATTRIBUTE_KEY).toLowerCase(Locale.ROOT))) {
+        if (containsKey(node.getAttributes(), REMOTE_SEGMENT_REPOSITORY_NAME_ATTRIBUTE_KEYS)
+            && containsKey(node.getAttributes(), List.of(REMOTE_STORE_SEGMENTS_ONLY_ATTRIBUTE_KEY))
+            && "true".equals(node.getAttributes().get(REMOTE_STORE_SEGMENTS_ONLY_ATTRIBUTE_KEY).toLowerCase(Locale.ROOT))) {
             repositoryNames.add(validateAttributeNonNull(node, REMOTE_SEGMENT_REPOSITORY_NAME_ATTRIBUTE_KEYS));
         } else if (containsKey(node.getAttributes(), REMOTE_SEGMENT_REPOSITORY_NAME_ATTRIBUTE_KEYS)
             || containsKey(node.getAttributes(), REMOTE_TRANSLOG_REPOSITORY_NAME_ATTRIBUTE_KEYS)) {
-            repositoryNames.add(validateAttributeNonNull(node, REMOTE_TRANSLOG_REPOSITORY_NAME_ATTRIBUTE_KEYS));
-            repositoryNames.add(validateAttributeNonNull(node, REMOTE_CLUSTER_STATE_REPOSITORY_NAME_ATTRIBUTE_KEYS));
-        } else if (containsKey(node.getAttributes(), REMOTE_CLUSTER_STATE_REPOSITORY_NAME_ATTRIBUTE_KEYS)) {
-            repositoryNames.add(validateAttributeNonNull(node, REMOTE_CLUSTER_STATE_REPOSITORY_NAME_ATTRIBUTE_KEYS));
-        }
+                repositoryNames.add(validateAttributeNonNull(node, REMOTE_TRANSLOG_REPOSITORY_NAME_ATTRIBUTE_KEYS));
+                repositoryNames.add(validateAttributeNonNull(node, REMOTE_CLUSTER_STATE_REPOSITORY_NAME_ATTRIBUTE_KEYS));
+            } else if (containsKey(node.getAttributes(), REMOTE_CLUSTER_STATE_REPOSITORY_NAME_ATTRIBUTE_KEYS)) {
+                repositoryNames.add(validateAttributeNonNull(node, REMOTE_CLUSTER_STATE_REPOSITORY_NAME_ATTRIBUTE_KEYS));
+            }
         if (containsKey(node.getAttributes(), REMOTE_ROUTING_TABLE_REPOSITORY_NAME_ATTRIBUTE_KEYS)) {
             repositoryNames.add(validateAttributeNonNull(node, REMOTE_ROUTING_TABLE_REPOSITORY_NAME_ATTRIBUTE_KEYS));
         }