feat: Add MongoDB client event logging via database option logClientEvents

spec/MongoStorageAdapter.spec.js

@@ -824,4 +824,243 @@ describe_only_db('mongo')('MongoStorageAdapter', () => {
       expect(roleIndexes.find(idx => idx.name === 'name_1')).toBeDefined();
     });
   });
+
+  describe('clientLogEvents', () => {
+    it('should log MongoDB client events when configured', async () => {
+      const logger = require('../lib/logger').logger;
+      const logSpy = spyOn(logger, 'warn');
+
+      const clientLogEvents = [
+        {
+          name: 'serverDescriptionChanged',
+          keys: ['address'],
+          logLevel: 'warn',
+        },
+      ];
+
+      const adapter = new MongoStorageAdapter({
+        uri: databaseURI,
+        mongoOptions: { clientLogEvents },
+      });
+
+      // Connect to trigger event listeners setup
+      await adapter.connect();
+
+      // Manually trigger the event to test the listener
+      const mockEvent = {
+        address: 'localhost:27017',
+        previousDescription: { type: 'Unknown' },
+        newDescription: { type: 'Standalone' },
+      };
+
+      adapter.client.emit('serverDescriptionChanged', mockEvent);
+
+      // Verify the log was called with the correct message
+      expect(logSpy).toHaveBeenCalledWith(
+        jasmine.stringMatching(/MongoDB client event serverDescriptionChanged:.*"address":"localhost:27017"/)
+      );
+
+      await adapter.handleShutdown();
+    });
+
+    it('should log entire event when keys are not specified', async () => {
+      const logger = require('../lib/logger').logger;
+      const logSpy = spyOn(logger, 'info');
+
+      const clientLogEvents = [
+        {
+          name: 'connectionPoolReady',
+          logLevel: 'info',
+        },
+      ];
+
+      const adapter = new MongoStorageAdapter({
+        uri: databaseURI,
+        mongoOptions: { clientLogEvents },
+      });
+
+      await adapter.connect();
+
+      const mockEvent = {
+        address: 'localhost:27017',
+        options: { maxPoolSize: 100 },
+      };
+
+      adapter.client.emit('connectionPoolReady', mockEvent);
+
+      expect(logSpy).toHaveBeenCalledWith(
+        jasmine.stringMatching(/MongoDB client event connectionPoolReady:.*"address":"localhost:27017".*"options"/)
+      );
+
+      await adapter.handleShutdown();
+    });
+
+    it('should extract nested keys using dot notation', async () => {
+      const logger = require('../lib/logger').logger;
+      const logSpy = spyOn(logger, 'warn');
+
+      const clientLogEvents = [
+        {
+          name: 'topologyDescriptionChanged',
+          keys: ['previousDescription.type', 'newDescription.type', 'newDescription.servers.size'],
+          logLevel: 'warn',
+        },
+      ];
+
+      const adapter = new MongoStorageAdapter({
+        uri: databaseURI,
+        mongoOptions: { clientLogEvents },
+      });
+
+      await adapter.connect();
+
+      const mockEvent = {
+        topologyId: 1,
+        previousDescription: { type: 'Unknown' },
+        newDescription: {
+          type: 'ReplicaSetWithPrimary',
+          servers: { size: 3 },
+        },
+      };
+
+      adapter.client.emit('topologyDescriptionChanged', mockEvent);
+
+      expect(logSpy).toHaveBeenCalledWith(
+        jasmine.stringMatching(/MongoDB client event topologyDescriptionChanged:.*"previousDescription.type":"Unknown".*"newDescription.type":"ReplicaSetWithPrimary".*"newDescription.servers.size":3/)
+      );
+
+      await adapter.handleShutdown();
+    });
+
+    it('should handle invalid log level gracefully', async () => {
+      const logger = require('../lib/logger').logger;
+      const infoSpy = spyOn(logger, 'info');
+
+      const clientLogEvents = [
+        {
+          name: 'connectionPoolReady',
+          keys: ['address'],
+          logLevel: 'invalidLogLevel', // Invalid log level
+        },
+      ];
+
+      const adapter = new MongoStorageAdapter({
+        uri: databaseURI,
+        mongoOptions: { clientLogEvents },
+      });
+
+      await adapter.connect();
+
+      const mockEvent = {
+        address: 'localhost:27017',
+      };
+
+      adapter.client.emit('connectionPoolReady', mockEvent);
+
+      // Should fallback to 'info' level
+      expect(infoSpy).toHaveBeenCalledWith(
+        jasmine.stringMatching(/MongoDB client event connectionPoolReady:.*"address":"localhost:27017"/)
+      );
+
+      await adapter.handleShutdown();
+    });
+
+    it('should handle Map and Set instances in events', async () => {
+      const logger = require('../lib/logger').logger;
+      const warnSpy = spyOn(logger, 'warn');
+
+      const clientLogEvents = [
+        {
+          name: 'customEvent',
+          logLevel: 'warn',
+        },
+      ];
+
+      const adapter = new MongoStorageAdapter({
+        uri: databaseURI,
+        mongoOptions: { clientLogEvents },
+      });
+
+      await adapter.connect();
+
+      const mockEvent = {
+        mapData: new Map([['key1', 'value1'], ['key2', 'value2']]),
+        setData: new Set([1, 2, 3]),
+      };
+
+      adapter.client.emit('customEvent', mockEvent);
+
+      // Should serialize Map and Set properly
+      expect(warnSpy).toHaveBeenCalledWith(
+        jasmine.stringMatching(/MongoDB client event customEvent:.*"mapData":\{"key1":"value1","key2":"value2"\}.*"setData":\[1,2,3\]/)
+      );
+
+      await adapter.handleShutdown();
+    });
+
+    it('should handle missing keys in event object', async () => {
+      const logger = require('../lib/logger').logger;
+      const infoSpy = spyOn(logger, 'info');
+
+      const clientLogEvents = [
+        {
+          name: 'testEvent',
+          keys: ['nonexistent.nested.key', 'another.missing'],
+          logLevel: 'info',
+        },
+      ];
+
+      const adapter = new MongoStorageAdapter({
+        uri: databaseURI,
+        mongoOptions: { clientLogEvents },
+      });
+
+      await adapter.connect();
+
+      const mockEvent = {
+        actualField: 'value',
+      };
+
+      adapter.client.emit('testEvent', mockEvent);
+
+      // Should handle missing keys gracefully with undefined values
+      expect(infoSpy).toHaveBeenCalledWith(
+        jasmine.stringMatching(/MongoDB client event testEvent:/)
+      );
+
+      await adapter.handleShutdown();
+    });
+
+    it('should handle circular references with fallback warning', async () => {
+      const logger = require('../lib/logger').logger;
+      const warnSpy = spyOn(logger, 'warn');
+
+      const clientLogEvents = [
+        {
+          name: 'circularEvent',
+          logLevel: 'info',
+        },
+      ];
+
+      const adapter = new MongoStorageAdapter({
+        uri: databaseURI,
+        mongoOptions: { clientLogEvents },
+      });
+
+      await adapter.connect();
+
+      // Create circular reference
+      const mockEvent = { name: 'test' };
+      mockEvent.self = mockEvent;
+
+      adapter.client.emit('circularEvent', mockEvent);
+
+      // Should fallback to warning when JSON.stringify fails
+      expect(warnSpy).toHaveBeenCalledWith(
+        jasmine.stringMatching(/MongoDB client event circularEvent logged with error:/)
+      );
+
+      await adapter.handleShutdown();
+    });
+  });
 });

src/Adapters/Storage/Mongo/MongoStorageAdapter.js

@@ -132,6 +132,7 @@ export class MongoStorageAdapter implements StorageAdapter {
   _mongoOptions: Object;
   _onchange: any;
   _stream: any;
+  _clientLogEvents: ?Array<any>;
   // Public
   connectionPromise: ?Promise<any>;
   database: any;
@@ -154,6 +155,7 @@ export class MongoStorageAdapter implements StorageAdapter {
     this.enableSchemaHooks = !!mongoOptions.enableSchemaHooks;
     this.schemaCacheTtl = mongoOptions.schemaCacheTtl;
     this.disableIndexFieldValidation = !!mongoOptions.disableIndexFieldValidation;
+    this._clientLogEvents = mongoOptions.clientLogEvents;
     // Remove Parse Server-specific options that should not be passed to MongoDB client
     // Note: We only delete from this._mongoOptions, not from the original mongoOptions object,
     // because other components (like DatabaseController) need access to these options
@@ -162,6 +164,7 @@ export class MongoStorageAdapter implements StorageAdapter {
       'schemaCacheTtl',
       'maxTimeMS',
       'disableIndexFieldValidation',
+      'clientLogEvents',
       'createIndexUserUsername',
       'createIndexUserUsernameCaseInsensitive',
       'createIndexUserEmail',
@@ -203,6 +206,44 @@ export class MongoStorageAdapter implements StorageAdapter {
         client.on('close', () => {
           delete this.connectionPromise;
         });
+
+        // Set up client event logging if configured
+        if (this._clientLogEvents && Array.isArray(this._clientLogEvents)) {
+          this._clientLogEvents.forEach(eventConfig => {
+            client.on(eventConfig.name, event => {
+              try {
+                let logData = {};
+                if (!eventConfig.keys || eventConfig.keys.length === 0) {
+                  logData = event;
+                } else {
+                  eventConfig.keys.forEach(keyPath => {
+                    logData[keyPath] = _.get(event, keyPath);
+                  });
+                }
+
+                // Validate log level exists, fallback to 'info'
+                const logLevel = typeof logger[eventConfig.logLevel] === 'function' ? eventConfig.logLevel : 'info';
+
+                // Safe JSON serialization with Map/Set support
+                const logMessage = `MongoDB client event ${eventConfig.name}: ${JSON.stringify(logData, (key, value) => {
+                  if (value instanceof Map) {
+                    return Object.fromEntries(value);
+                  }
+                  if (value instanceof Set) {
+                    return Array.from(value);
+                  }
+                  return value;
+                })}`;
+
+                logger[logLevel](logMessage);
+              } catch (error) {
+                // Fallback if serialization completely fails
+                logger.warn(`MongoDB client event ${eventConfig.name} logged with error: ${error.message}`);
+              }
+            });
+          });
+        }
+
         this.client = client;
         this.database = database;
       })

src/Options/Definitions.js

@@ -1117,6 +1117,12 @@ module.exports.DatabaseOptions = {
       'The MongoDB driver option to specify the amount of time in milliseconds to wait for a connection attempt to finish before trying the next address when using the autoSelectFamily option. If set to a positive integer less than 10, the value 10 is used instead.',
     action: parsers.numberParser('autoSelectFamilyAttemptTimeout'),
   },
+  clientLogEvents: {
+    env: 'PARSE_SERVER_DATABASE_CLIENT_LOG_EVENTS',
+    help:
+      "An array of MongoDB client event configurations to enable logging of specific events. Each configuration object should contain:<br><ul><li>`name` (the event name, e.g., 'topologyDescriptionChanged', 'serverDescriptionChanged', 'connectionPoolCleared', 'connectionPoolReady')</li><li>`keys` (optional array of dot-notation paths to extract specific data from the event object; if not provided or empty, the entire event object will be logged)</li><li>`logLevel` (the log level to use for this event: 'error', 'warn', 'info', 'debug', etc.).</li></ul>",
+    action: parsers.arrayParser,
+  },
   compressors: {
     env: 'PARSE_SERVER_DATABASE_COMPRESSORS',
     help:

src/Options/index.js

@@ -608,6 +608,15 @@ export interface FileUploadOptions {
   enableForPublic: ?boolean;
 }
 
+export type ClientLogEvent = {
+  /* The MongoDB driver event name to listen for. */
+  name: string,
+  /* Optional array of dot-notation paths to extract specific data from the event object. If not provided or empty, the entire event object will be logged. */
+  keys?: string[],
+  /* The log level to use for this event. */
+  logLevel: string,
+};
+
 export interface DatabaseOptions {
   /* Enables database real-time hooks to update single schema cache. Set to `true` if using multiple Parse Servers instances connected to the same database. Failing to do so will cause a schema change to not propagate to all instances and re-syncing will only happen when the instances restart. To use this feature with MongoDB, a replica set cluster with [change stream](https://docs.mongodb.com/manual/changeStreams/#availability) support is required.
   :DEFAULT: false */
@@ -725,6 +734,8 @@ export interface DatabaseOptions {
   createIndexRoleName: ?boolean;
   /* Set to `true` to disable validation of index fields. When disabled, indexes can be created even if the fields do not exist in the schema. This can be useful when creating indexes on fields that will be added later. */
   disableIndexFieldValidation: ?boolean;
+  /* An array of MongoDB client event configurations to enable logging of specific events. Each configuration object should contain:<br><ul><li>`name` (the event name, e.g., 'topologyDescriptionChanged', 'serverDescriptionChanged', 'connectionPoolCleared', 'connectionPoolReady')</li><li>`keys` (optional array of dot-notation paths to extract specific data from the event object; if not provided or empty, the entire event object will be logged)</li><li>`logLevel` (the log level to use for this event: 'error', 'warn', 'info', 'debug', etc.).</li></ul> */
+  clientLogEvents: ?(ClientLogEvent[]);
 }
 
 export interface AuthAdapter {