Tuesday, 19 January 2016

Using SKIP LOCKED feature in DB Adapter polling

Last few days I spent with describing a Throttle mechanism using the DB Adapter. Today the 'Distributed Polling' functionality of the DB Adapter was mentioned to me, which uses the SKIP LOCKED clausule of the database.

On one of the pages you'll get to check the 'Distributed Polling' option:
Leave it like it is, since it adds the 'SKIP LOCKED' option in the 'FOR UPDATE' clausule.

In my example screendump I set the Database Rows per Transaction, but you might want to set in a sensible higher value with regards to the 'RowsPerPollingInterval' that you need to set yourself in the JCA file:

The 'RowsPerPollingInterval' is not an option in the UI, unfortunately. You might want to set this as a multiple to the MaxTransactionSize (in the UI denoted as 'Database Rows per Transaction').

A great explanation for this functionality is this A-Team blogpost. Unfortunately the link to the documentation about 'SKIP LOCKED' in that post is broken. I found this one. Nice thing is that it suggests using AQ as preferred solution in stead of SKIP LOCKED.

Maybe a better way for throttling is using the AQ Adapter together with the properties

No comments :