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From "Alexander Kolbasov (JIRA)" <j...@apache.org>
Subject [jira] [Issue Comment Deleted] (HIVE-16164) Provide mechanism for passing HMS notification ID between transactional and non-transactional listeners.
Date Fri, 10 Mar 2017 02:38:37 GMT

     [ https://issues.apache.org/jira/browse/HIVE-16164?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Alexander Kolbasov updated HIVE-16164:
--------------------------------------
    Comment: was deleted

(was: Note that in the code snippet above the non-transactional listener gets a new createTableEvent,
so anything set in the environment context of the transactional listener os lost. Why the
event is not reused between transactional and non-transactional listeners?)

> Provide mechanism for passing HMS notification ID between transactional and non-transactional
listeners.
> --------------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-16164
>                 URL: https://issues.apache.org/jira/browse/HIVE-16164
>             Project: Hive
>          Issue Type: Improvement
>          Components: Metastore
>            Reporter: Sergio Peña
>            Assignee: Sergio Peña
>
> The HMS DB notification listener currently stores an event ID on the HMS backend DB so
that external applications (such as backup apps) can request incremental notifications based
on the last event ID requested.
> The HMS DB notification and backup applications are asynchronous. However, there are
sometimes that applications may be required to be in sync with the latest HMS event in order
to process an action. These applications will provide a listener implementation that is called
by the HMS after an HMS transaction happened.
> The problem is that the listener running after the transaction (or during the non-transactional
context) may need the DB event ID in order to sync all events happened previous to that event
ID, but this ID is never passed to the non-transactional listeners.
> We can pass this event information through the EnvironmentContext found on each ListenerEvent
implementations (such as CreateTableEvent), and send the EnvironmentContext to the non-transactional
listeners to get the event ID.
> The DbNotificactionListener already knows the event ID after calling the ObjectStore.addNotificationEvent().
We just need to set this event ID to the EnvironmentContext from each of the event notifications
and make sure that this EnvironmentContext is sent to the non-transactional listeners.
> Here's the code example when creating a table on {{create_table_core}}:
> {noformat}
>  ms.createTable(tbl);
>   if (transactionalListeners.size() > 0) {
>     CreateTableEvent createTableEvent = new CreateTableEvent(tbl, true, this);
>     createTableEvent.setEnvironmentContext(envContext);
>     for (MetaStoreEventListener transactionalListener : transactionalListeners) {
>       transactionalListener.onCreateTable(createTableEvent);         // <- Here the
notification ID is generated
>     }
>   }
>   success = ms.commitTransaction();
> } finally {
>   if (!success) {
>     ms.rollbackTransaction();
>     if (madeDir) {
>       wh.deleteDir(tblPath, true);
>     }
>   }
>   for (MetaStoreEventListener listener : listeners) {
>     CreateTableEvent createTableEvent =
>         new CreateTableEvent(tbl, success, this);
>     createTableEvent.setEnvironmentContext(envContext);
>     listener.onCreateTable(createTableEvent);                        // <- Here we
would like to consume notification ID
>   }
> {noformat}
> We could use a specific key name that will be used on the EnvironmentContext, such as
DB_NOTIFICATION_EVENT_ID.



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