openvidu-server: protect concurrent recording start methods

openvidu-server/src/main/java/io/openvidu/server/core/Session.java

@@ -80,7 +80,7 @@ public class Session implements SessionInterface {
 
 	/**
 	 * This lock protects initialization of ALWAYS recordings upon first user
-	 * publishing
+	 * publishing, as well as POST /api/recordings/start
 	 */
 	public Lock recordingLock = new ReentrantLock();
 

openvidu-server/src/main/java/io/openvidu/server/recording/service/RecordingManager.java

@@ -230,6 +230,13 @@ public class RecordingManager {
 	}
 
 	public Recording startRecording(Session session, RecordingProperties properties) throws OpenViduException {
+		try {
+			if (session.recordingLock.tryLock(15, TimeUnit.SECONDS)) {
+				try {
+					if (sessionIsBeingRecorded(session.getSessionId())) {
+						throw new OpenViduException(Code.RECORDING_START_ERROR_CODE,
+								"Concurrent start of recording for session " + session.getSessionId());
+					} else {
 						Recording recording = null;
 						try {
 							switch (properties.outputMode()) {
@@ -263,6 +270,20 @@ public class RecordingManager {
 						}
 						return recording;
 					}
+				} finally {
+					session.recordingLock.unlock();
+				}
+			} else {
+				throw new OpenViduException(Code.RECORDING_START_ERROR_CODE,
+						"Timeout waiting for recording Session lock to be available for session "
+								+ session.getSessionId());
+			}
+		} catch (InterruptedException e) {
+			throw new OpenViduException(Code.RECORDING_START_ERROR_CODE,
+					"InterruptedException waiting for recording Session lock to be available for session "
+							+ session.getSessionId());
+		}
+	}
 
 	public Recording stopRecording(Session session, String recordingId, EndReason reason) {
 		Recording recording;