[Cluster] Update the default AuthorisationService to allow requests necessary for Cluster Standby

aeron-cluster/src/main/java/io/aeron/cluster/AllowBackupAndStandbyAuthorisationService.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2014-2025 Real Logic Limited.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.aeron.cluster;
+
+import io.aeron.cluster.codecs.BackupQueryDecoder;
+import io.aeron.cluster.codecs.HeartbeatRequestDecoder;
+import io.aeron.cluster.codecs.MessageHeaderDecoder;
+import io.aeron.cluster.codecs.StandbySnapshotDecoder;
+import io.aeron.security.AuthorisationService;
+
+/**
+ * An {@link AuthorisationService} that allows the actions required by Cluster Backup
+ * and Aeron Cluster Standby.
+ */
+public enum AllowBackupAndStandbyAuthorisationService implements AuthorisationService
+{
+    /**
+     * As there is no instance state then this object can be used to save on allocation.
+     */
+    INSTANCE;
+
+    /**
+     * {@inheritDoc}
+     */
+    public boolean isAuthorised(
+        final int protocolId,
+        final int actionId,
+        final Object type,
+        final byte[] encodedPrincipal)
+    {
+        return MessageHeaderDecoder.SCHEMA_ID == protocolId &&
+            (BackupQueryDecoder.TEMPLATE_ID == actionId || HeartbeatRequestDecoder.TEMPLATE_ID == actionId ||
+                StandbySnapshotDecoder.TEMPLATE_ID == actionId);
+    }
+}

aeron-cluster/src/main/java/io/aeron/cluster/ConsensusModule.java

@@ -790,15 +790,12 @@ public static final class Configuration
         public static final String AUTHORISATION_SERVICE_SUPPLIER_PROP_NAME =
             "aeron.cluster.authorisation.service.supplier";
 
-        static final AuthorisationService ALLOW_ONLY_BACKUP_QUERIES = (protocolId, actionId, type, encodedPrincipal) ->
-            MessageHeaderDecoder.SCHEMA_ID == protocolId && BackupQueryDecoder.TEMPLATE_ID == actionId;
-
         /**
          * Default {@link AuthorisationServiceSupplier} that returns {@link AuthorisationService} that forbids all
          * command from being executed (i.e. {@link AuthorisationService#DENY_ALL}).
          */
         public static final AuthorisationServiceSupplier DEFAULT_AUTHORISATION_SERVICE_SUPPLIER =
-            () -> ALLOW_ONLY_BACKUP_QUERIES;
+            () -> AllowBackupAndStandbyAuthorisationService.INSTANCE;
 
         /**
          * Size in bytes of the error buffer for the cluster.

aeron-cluster/src/test/java/io/aeron/cluster/ConsensusModuleContextTest.java

@@ -67,7 +67,6 @@
 import static io.aeron.AeronCounters.CLUSTER_ELECTION_COUNT_TYPE_ID;
 import static io.aeron.AeronCounters.CLUSTER_LEADERSHIP_TERM_ID_TYPE_ID;
 import static io.aeron.AeronCounters.NODE_CONTROL_TOGGLE_TYPE_ID;
-import static io.aeron.cluster.ConsensusModule.Configuration.ALLOW_ONLY_BACKUP_QUERIES;
 import static io.aeron.cluster.ConsensusModule.Configuration.AUTHENTICATOR_SUPPLIER_PROP_NAME;
 import static io.aeron.cluster.ConsensusModule.Configuration.AUTHORISATION_SERVICE_SUPPLIER_PROP_NAME;
 import static io.aeron.cluster.ConsensusModule.Configuration.CLUSTER_CLOCK_PROP_NAME;
@@ -247,9 +246,9 @@ void rejectInvalidLogChannelParameters()
     }
 
     @Test
-    void defaultAuthorisationServiceSupplierReturnsADenyAllAuthorisationService()
+    void defaultAuthorisationServiceSupplierAllowsBackupAndStandby()
     {
-        assertSame(ALLOW_ONLY_BACKUP_QUERIES, DEFAULT_AUTHORISATION_SERVICE_SUPPLIER.get());
+        assertSame(AllowBackupAndStandbyAuthorisationService.INSTANCE, DEFAULT_AUTHORISATION_SERVICE_SUPPLIER.get());
     }
 
     @Test