Database log capture that publishes transactions to multiple targets to handle unavailable targets by separating the publishing of subscriptions and subsequently recombining the publishing

Abstract

A first log reader publishes first messages to a plurality of queues. The messages comprise changes for transactions extracted from a log by the first log reader. In response to one of the queues becoming unavailable, a second log reader is launched to read and extract from the log, and to publish second messages comprising changes for transactions extracted from the log by the second log reader to the unavailable queue as a catch-up queue. In response to the catch-up queue becoming available and the second log reader reaching the end of the log, the publishing of the second messages for the catch-up queue is transferred from the second log reader to the first log reader.