anishek created HIVE-16738: ------------------------------ Summary: Notification ID generation in DBNotification might not be unique Key: HIVE-16738 URL: https://issues.apache.org/jira/browse/HIVE-16738 Project: Hive Issue Type: Bug Components: HiveServer2 Affects Versions: 3.0.0 Reporter: anishek Assignee: anishek Fix For: 3.0.0
Going to explain the problem in scope of "replication" feature for hive 2 that is being built, as it is easier to explain: To allow replication to work we need to set "hive.metastore.transactional.event.listeners" to DBNotificationListener. For use cases where there are multiple HiveServer2 Instances running {code} private void process(NotificationEvent event, ListenerEvent listenerEvent) throws MetaException { event.setMessageFormat(msgFactory.getMessageFormat()); synchronized (NOTIFICATION_TBL_LOCK) { LOG.debug("DbNotificationListener: Processing : {}:{}", event.getEventId(), event.getMessage()); HMSHandler.getMSForConf(hiveConf).addNotificationEvent(event); } // Set the DB_NOTIFICATION_EVENT_ID for future reference by other listeners. if (event.isSetEventId()) { listenerEvent.putParameter( MetaStoreEventListenerConstants.DB_NOTIFICATION_EVENT_ID_KEY_NAME, Long.toString(event.getEventId())); } } {code} the above code in DBNotificationListner having the object lock wont be guarantee enough to make sure that all events get a unique id. The transaction isolation level at the db "read-comitted" or "repeatable-read" would also not guarantee the same, unless a lock is at the db level preferably on table {{NOTIFICATION_SEQUENCE}} which only has one row. -- This message was sent by Atlassian JIRA (v6.3.15#6346)