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)
