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Posted to issues@hive.apache.org by "anishek (JIRA)" <ji...@apache.org> on 2017/08/09 06:55:00 UTC
[jira] [Resolved] (HIVE-16738) Notification ID generation in
DBNotification might not be unique across HS2 instances.
[ https://issues.apache.org/jira/browse/HIVE-16738?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
anishek resolved HIVE-16738.
----------------------------
Resolution: Duplicate
> Notification ID generation in DBNotification might not be unique across HS2 instances.
> --------------------------------------------------------------------------------------
>
> 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.
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