Add MongoClientSettingsBuilderCustomizer hook for the Mongo client

grails-data-mongodb/core/src/main/groovy/org/grails/datastore/mapping/mongo/connections/MongoClientSettingsBuilderCustomizer.groovy

@@ -0,0 +1,57 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you 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 org.grails.datastore.mapping.mongo.connections
+
+import com.mongodb.MongoClientSettings
+
+/**
+ * Callback interface that can be implemented by beans wishing to customize the
+ * {@link MongoClientSettings.Builder} used to construct the underlying
+ * {@link com.mongodb.client.MongoClient} before it is created.
+ *
+ * <p>Any beans of this type found in the application context are applied, in order,
+ * to the builder for the default connection source. This is the supported extension
+ * point for settings that cannot be expressed through {@code grails.mongodb.*}
+ * configuration — for example registering a driver
+ * {@link com.mongodb.event.CommandListener} for metrics/tracing, tuning the connection
+ * pool, or configuring read/write concerns programmatically.</p>
+ *
+ * <pre class="code">
+ * &#64;Bean
+ * MongoClientSettingsBuilderCustomizer mongoMetrics(MeterRegistry registry) {
+ *     return { builder -> builder.addCommandListener(new MongoMetricsCommandListener(registry)) }
+ * }
+ * </pre>
+ *
+ * <p>Mirrors the semantics of Spring Boot's
+ * {@code MongoClientSettingsBuilderCustomizer}.</p>
+ *
+ * @since 7.2
+ */
+@FunctionalInterface
+interface MongoClientSettingsBuilderCustomizer {
+
+    /**
+     * Customize the {@link MongoClientSettings.Builder}.
+     *
+     * @param builder the builder to customize, never {@code null}
+     */
+    void customize(MongoClientSettings.Builder builder)
+}

grails-data-mongodb/core/src/main/groovy/org/grails/datastore/mapping/mongo/connections/MongoConnectionSourceFactory.groovy

@@ -63,6 +63,15 @@ class MongoConnectionSourceFactory extends AbstractConnectionSourceFactory<Mongo
     @Autowired(required = false)
     List<Codec> codecs = []
 
+    /**
+     * Optional customizers applied to the {@link MongoClientSettings.Builder} of the
+     * default connection source before the {@link MongoClient} is created. This is the
+     * supported hook for settings that have no {@code grails.mongodb.*} equivalent — e.g.
+     * registering a driver {@link com.mongodb.event.CommandListener} for metrics/tracing.
+     */
+    @Autowired(required = false)
+    List<MongoClientSettingsBuilderCustomizer> clientSettingsCustomizers = []
+
     @Override
     Serializable getConnectionSourcesConfigurationKey() {
         return MongoSettings.SETTING_CONNECTIONS
@@ -98,6 +107,9 @@ class MongoConnectionSourceFactory extends AbstractConnectionSourceFactory<Mongo
         }
 
         builder.applyConnectionString(settings.url)
+        for (MongoClientSettingsBuilderCustomizer customizer : clientSettingsCustomizers) {
+            customizer.customize(builder)
+        }
         MongoClient client = MongoClients.create(builder.build())
         return new DefaultConnectionSource<MongoClient, MongoConnectionSourceSettings>(name, client, settings)
     }

grails-data-mongodb/core/src/test/groovy/org/grails/datastore/mapping/mongo/config/MongoConnectionSourceFactorySpec.groovy

@@ -20,10 +20,13 @@ package org.grails.datastore.mapping.mongo.config
 
 import com.mongodb.client.MongoClient
 import com.mongodb.ReadPreference
+import com.mongodb.MongoClientSettings
+import com.mongodb.event.CommandListener
 import org.grails.datastore.mapping.core.DatastoreUtils
 import org.grails.datastore.mapping.core.connections.ConnectionSource
 import org.grails.datastore.mapping.core.connections.ConnectionSources
 import org.grails.datastore.mapping.core.connections.ConnectionSourcesInitializer
+import org.grails.datastore.mapping.mongo.connections.MongoClientSettingsBuilderCustomizer
 import org.grails.datastore.mapping.mongo.connections.MongoConnectionSourceFactory
 import org.grails.datastore.mapping.mongo.connections.MongoConnectionSourceSettings
 import spock.lang.Specification
@@ -82,4 +85,47 @@ class MongoConnectionSourceFactorySpec extends Specification {
         sources?.close()
     }
 
+    void "test a registered MongoClientSettingsBuilderCustomizer is applied to the default connection source"() {
+        given: "a customizer that records its invocation and registers a command listener"
+        CommandListener listener = new CommandListener() {}
+        MongoClientSettings.Builder captured = null
+        MongoClientSettingsBuilderCustomizer customizer = { MongoClientSettings.Builder builder ->
+            captured = builder
+            builder.addCommandListener(listener)
+        }
+
+        when: "the factory builds connection sources with the customizer registered"
+        MongoConnectionSourceFactory factory = new MongoConnectionSourceFactory(clientSettingsCustomizers: [customizer])
+        ConnectionSources<MongoClient, MongoConnectionSourceSettings> sources = ConnectionSourcesInitializer.create(factory, DatastoreUtils.createPropertyResolver(
+                (MongoSettings.SETTING_URL): "mongodb://localhost/myDb"
+        ))
+
+        then: "the customizer was invoked and its command listener applied to the built client settings"
+        sources.defaultConnectionSource != null
+        captured != null
+        captured.build().commandListeners.contains(listener)
+
+        cleanup:
+        sources?.close()
+    }
+
+    void "test multiple MongoClientSettingsBuilderCustomizers are applied in registration order"() {
+        given: "two customizers that append to a shared list"
+        List<String> order = []
+        MongoClientSettingsBuilderCustomizer first = { MongoClientSettings.Builder builder -> order << 'first' }
+        MongoClientSettingsBuilderCustomizer second = { MongoClientSettings.Builder builder -> order << 'second' }
+
+        when: "the factory builds connection sources with both customizers registered"
+        MongoConnectionSourceFactory factory = new MongoConnectionSourceFactory(clientSettingsCustomizers: [first, second])
+        ConnectionSources<MongoClient, MongoConnectionSourceSettings> sources = ConnectionSourcesInitializer.create(factory, DatastoreUtils.createPropertyResolver(
+                (MongoSettings.SETTING_URL): "mongodb://localhost/myDb"
+        ))
+
+        then: "both ran, in order"
+        order == ['first', 'second']
+
+        cleanup:
+        sources?.close()
+    }
+
 }