openvidu-server: improved concurrent Session initializaion

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

@@ -304,18 +304,25 @@ public abstract class SessionManager {
 		return null;
 	}
 
+	/**
+	 * @return null if concurrent storing of session
+	 */
 	public Session storeSessionNotActive(String sessionId, SessionProperties sessionProperties) {
 		Session sessionNotActive = this
 				.storeSessionNotActive(new Session(sessionId, sessionProperties, openviduConfig, recordingManager));
-		sessionEventsHandler.onSessionCreated(sessionNotActive);
+		if (sessionNotActive == null) {
-		return sessionNotActive;
+			return null;
+		} else {
+			sessionEventsHandler.onSessionCreated(sessionNotActive);
+			return sessionNotActive;
+		}
 	}
 
 	public Session storeSessionNotActive(Session sessionNotActive) {
 		final String sessionId = sessionNotActive.getSessionId();
 		if (this.sessionsNotActive.putIfAbsent(sessionId, sessionNotActive) != null) {
 			log.warn("Concurrent initialization of session {}", sessionId);
-			return this.sessionsNotActive.get(sessionId);
+			return null;
 		}
 		this.initializeCollections(sessionId);
 		return sessionNotActive;

openvidu-server/src/main/java/io/openvidu/server/rest/SessionRestController.java

@@ -121,11 +121,15 @@ public class SessionRestController {
 		}
 
 		Session sessionNotActive = sessionManager.storeSessionNotActive(sessionId, sessionProperties);
-		log.info("New session {} created {}", sessionId, this.sessionManager.getSessionsWithNotActive().stream()
-				.map(Session::getSessionId).collect(Collectors.toList()).toString());
 
-		return new ResponseEntity<>(sessionNotActive.toJson(false, false).toString(), RestUtils.getResponseHeaders(),
+		if (sessionNotActive == null) {
-				HttpStatus.OK);
+			return new ResponseEntity<>(HttpStatus.CONFLICT);
+		} else {
+			log.info("New session {} created {}", sessionId, this.sessionManager.getSessionsWithNotActive().stream()
+					.map(Session::getSessionId).collect(Collectors.toList()).toString());
+			return new ResponseEntity<>(sessionNotActive.toJson(false, false).toString(),
+					RestUtils.getResponseHeaders(), HttpStatus.OK);
+		}
 	}
 
 	@RequestMapping(value = "/sessions/{sessionId}", method = RequestMethod.GET)