What is a bookmark subscription?

A 'bookmark' is a special value that identifies a location in the AMPS transaction log. A bookmark subscription is similar to a regular subscription except that it contains a bookmark that AMPS will use to replay messages from the transaction log starting at the message just after the bookmark point in the transaction log. At the end of the replay, the subscription will become live similar to a regular subscription. Each message delivered to an application that matches a bookmark subscription will contain a bookmark that can be recorded and used with subsequent bookmark subscribe requests so that the application does not miss any messages regardless of its up/down state.

The AMPS Client libraries include bookmark stores for managing the bookmarks that an application has seen and processed. These classes correctly handle edge cases for replication fabrics with multiple active instances. Using these classes is recommended rather than managing bookmarks in the application. Recent versions of the AMPS Client libraries include an interface for managing persistence to an external system (including AMPS itself) without having to implement a complete bookmark store.