Use singleton instance for default project-id (#123677)

No need to create new instances for the default project-id. We can use
the singleton field which should speeds up key comparsion for Map.get
operations.

Relates: #123662

Author: ywangd

server/src/main/java/org/elasticsearch/cluster/block/ClusterBlocks.java

@@ -438,7 +438,7 @@ private static void writeBlockSet(Set<ClusterBlock> blocks, StreamOutput out) th
     public static ClusterBlocks readFrom(StreamInput in) throws IOException {
         if (in.getTransportVersion().onOrAfter(TransportVersions.MULTI_PROJECT)) {
             final Set<ClusterBlock> global = readBlockSet(in);
-            final Map<ProjectId, ProjectBlocks> projectBlocksMap = in.readImmutableMap(ProjectId::new, ProjectBlocks::readFrom);
+            final Map<ProjectId, ProjectBlocks> projectBlocksMap = in.readImmutableMap(ProjectId::readFrom, ProjectBlocks::readFrom);
             if (global.isEmpty()
                 && noProjectOrDefaultProjectOnly(projectBlocksMap)
                 && projectBlocksMap.getOrDefault(Metadata.DEFAULT_PROJECT_ID, ProjectBlocks.EMPTY).indices().isEmpty()) {

server/src/main/java/org/elasticsearch/cluster/metadata/Metadata.java

@@ -88,7 +88,7 @@ public class Metadata implements Diffable<Metadata>, ChunkedToXContent {
     public static final String UNKNOWN_CLUSTER_UUID = "_na_";
     // TODO multi-project: verify that usages are really expected to work on the default project only,
     // and that they are not a stop-gap solution to make the tests pass
-    public static final ProjectId DEFAULT_PROJECT_ID = new ProjectId("default");
+    public static final ProjectId DEFAULT_PROJECT_ID = ProjectId.DEFAULT;
 
     public enum XContentContext {
         /* Custom metadata should be returned as part of API call */
@@ -1154,7 +1154,7 @@ public static Metadata readFrom(StreamInput in) throws IOException {
                 builder.put(ReservedStateMetadata.readFrom(in));
             }
 
-            builder.projectMetadata(in.readMap(ProjectId::new, ProjectMetadata::readFrom));
+            builder.projectMetadata(in.readMap(ProjectId::readFrom, ProjectMetadata::readFrom));
         }
         return builder.build();
     }

server/src/main/java/org/elasticsearch/cluster/metadata/ProjectId.java

@@ -19,17 +19,39 @@
 import org.elasticsearch.xcontent.XContentParser;
 
 import java.io.IOException;
+import java.util.Objects;
 
-public record ProjectId(String id) implements Writeable, ToXContent {
+public class ProjectId implements Writeable, ToXContent {
 
-    public static final Reader<ProjectId> READER = ProjectId::new;
+    private static final String DEFAULT_STRING = "default";
+    public static final ProjectId DEFAULT = new ProjectId(DEFAULT_STRING);
+    public static final Reader<ProjectId> READER = ProjectId::readFrom;
     private static final int MAX_LENGTH = 128;
 
-    public ProjectId {
+    private final String id;
+
+    private ProjectId(String id) {
         if (Strings.isNullOrBlank(id)) {
             throw new IllegalArgumentException("project-id cannot be empty");
         }
-        assert isValidFormatId(id) : "project-id [" + id + "] must be alphanumeric ASCII with up to " + MAX_LENGTH + " chars";
+        if (isValidFormatId(id) == false) {
+            final var message = "project-id [" + id + "] must be alphanumeric ASCII with up to " + MAX_LENGTH + " chars";
+            assert false : message;
+            throw new IllegalArgumentException(message);
+        }
+        this.id = id;
+    }
+
+    public String id() {
+        return id;
+    }
+
+    public static ProjectId fromId(String id) {
+        if (DEFAULT_STRING.equals(id)) {
+            return DEFAULT;
+        } else {
+            return new ProjectId(id);
+        }
     }
 
     static boolean isValidFormatId(String id) {
@@ -53,8 +75,8 @@ private static boolean isValidIdChar(char c) {
         return (c >= '0' && c <= '9') || (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || c == '_' || c == '-';
     }
 
-    public ProjectId(StreamInput in) throws IOException {
-        this(in.readString());
+    public static ProjectId readFrom(StreamInput in) throws IOException {
+        return fromId(in.readString());
     }
 
     @Override
@@ -79,4 +101,16 @@ public static ProjectId ofNullable(@Nullable String id, @Nullable ProjectId fall
     public String toString() {
         return this.id;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (o == null || getClass() != o.getClass()) return false;
+        ProjectId projectId = (ProjectId) o;
+        return Objects.equals(id, projectId.id);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(id);
+    }
 }

server/src/main/java/org/elasticsearch/cluster/metadata/ProjectMetadata.java

@@ -2136,7 +2136,7 @@ public Iterator<? extends ToXContent> toXContentChunked(ToXContent.Params p) {
     }
 
     public static ProjectMetadata readFrom(StreamInput in) throws IOException {
-        ProjectId id = new ProjectId(in);
+        ProjectId id = ProjectId.readFrom(in);
         Builder builder = builder(id);
         Function<String, MappingMetadata> mappingLookup;
         Map<String, MappingMetadata> mappingMetadataMap = in.readMapValues(MappingMetadata::new, MappingMetadata::getSha256);

server/src/main/java/org/elasticsearch/cluster/project/AbstractProjectResolver.java

@@ -50,7 +50,7 @@ public ProjectId getProjectId() {
         if (headerValue == null) {
             return getFallbackProjectId();
         }
-        return new ProjectId(headerValue);
+        return ProjectId.fromId(headerValue);
     }
 
     @Override
@@ -89,7 +89,7 @@ public boolean supportsMultipleProjects() {
     }
 
     protected static ProjectMetadata findProject(Metadata metadata, String headerValue) {
-        var project = metadata.projects().get(new ProjectId(headerValue));
+        var project = metadata.projects().get(ProjectId.fromId(headerValue));
         if (project == null) {
             throw new IllegalArgumentException("Could not find project with id [" + headerValue + "]");
         }

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

@@ -179,7 +179,7 @@ public static Diff<GlobalRoutingTable> readDiffFrom(StreamInput in) throws IOExc
     }
 
     public static GlobalRoutingTable readFrom(StreamInput in) throws IOException {
-        final var table = in.readImmutableOpenMap(ProjectId::new, RoutingTable::readFrom);
+        final var table = in.readImmutableOpenMap(ProjectId::readFrom, RoutingTable::readFrom);
         return new GlobalRoutingTable(table);
     }
 

server/src/main/java/org/elasticsearch/cluster/routing/allocation/command/AbstractAllocateAllocationCommand.java

@@ -109,7 +109,7 @@ protected AbstractAllocateAllocationCommand(StreamInput in) throws IOException {
         shardId = in.readVInt();
         node = in.readString();
         if (in.getTransportVersion().onOrAfter(TransportVersions.MULTI_PROJECT)) {
-            projectId = new ProjectId(in);
+            projectId = ProjectId.readFrom(in);
         } else {
             projectId = Metadata.DEFAULT_PROJECT_ID;
         }

server/src/main/java/org/elasticsearch/cluster/routing/allocation/command/CancelAllocationCommand.java

@@ -84,7 +84,7 @@ public CancelAllocationCommand(StreamInput in) throws IOException {
         node = in.readString();
         allowPrimary = in.readBoolean();
         if (in.getTransportVersion().onOrAfter(TransportVersions.MULTI_PROJECT)) {
-            projectId = new ProjectId(in);
+            projectId = ProjectId.readFrom(in);
         } else {
             projectId = Metadata.DEFAULT_PROJECT_ID;
         }

server/src/main/java/org/elasticsearch/cluster/routing/allocation/command/MoveAllocationCommand.java

@@ -69,7 +69,7 @@ public MoveAllocationCommand(StreamInput in) throws IOException {
         fromNode = in.readString();
         toNode = in.readString();
         if (in.getTransportVersion().onOrAfter(TransportVersions.MULTI_PROJECT)) {
-            projectId = new ProjectId(in);
+            projectId = ProjectId.readFrom(in);
         } else {
             projectId = Metadata.DEFAULT_PROJECT_ID;
         }

server/src/test/java/org/elasticsearch/action/admin/cluster/health/TransportClusterHealthActionTests.java

@@ -41,21 +41,21 @@ public void testWaitForInitializingShards() throws Exception {
         final String[] indices = { "test" };
         final ClusterHealthRequest request = new ClusterHealthRequest(TEST_REQUEST_TIMEOUT);
         request.waitForNoInitializingShards(true);
-        var projectId = new ProjectId(randomUUID());
+        var projectId = randomUniqueProjectId();
         ClusterState clusterState = randomClusterStateWithInitializingShards("test", 0, projectId);
         var project = clusterState.metadata().getProject(projectId);
         ClusterHealthResponse response = createResponse(indices, clusterState, project);
         assertThat(TransportClusterHealthAction.prepareResponse(request, response, project, null), equalTo(1));
 
         request.waitForNoInitializingShards(true);
-        projectId = new ProjectId(randomUUID());
+        projectId = randomUniqueProjectId();
         clusterState = randomClusterStateWithInitializingShards("test", between(1, 10), projectId);
         project = clusterState.metadata().getProject(projectId);
         response = createResponse(indices, clusterState, project);
         assertThat(TransportClusterHealthAction.prepareResponse(request, response, project, null), equalTo(0));
 
         request.waitForNoInitializingShards(false);
-        projectId = new ProjectId(randomUUID());
+        projectId = randomUniqueProjectId();
         clusterState = randomClusterStateWithInitializingShards("test", randomInt(20), projectId);
         project = clusterState.metadata().getProject(projectId);
         response = createResponse(indices, clusterState, project);
@@ -67,7 +67,7 @@ public void testWaitForAllShards() {
         final ClusterHealthRequest request = new ClusterHealthRequest(TEST_REQUEST_TIMEOUT);
         request.waitForActiveShards(ActiveShardCount.ALL);
 
-        var projectId = new ProjectId(randomUUID());
+        var projectId = randomUniqueProjectId();
         ClusterState clusterState = randomClusterStateWithInitializingShards("test", 1, projectId);
         var project = clusterState.metadata().getProject(projectId);
         ClusterHealthResponse response = createResponse(indices, clusterState, project);
@@ -125,7 +125,7 @@ ClusterState randomClusterStateWithInitializingShards(String index, final int in
         }
 
         var projects = randomMap(0, 5, () -> {
-            var id = new ProjectId(randomUUID());
+            var id = randomUniqueProjectId();
             return Tuple.tuple(id, ProjectMetadata.builder(id).build());
         });
         return ClusterState.builder(ClusterName.DEFAULT)