The Change Log Daemon for CUE Content Store provides a means of tracking changes made in the CUE Content Store database. It can be used in the implementation of a wide range of extensions to CUE applications, such as:

  • Exporting content from the Content Store to some other system (a print system for example).

  • Importing content from an external system when certain types of change occur.

  • Processing content as it is added to the Content Store (advanced text analysis for example).

In all these cases, the Change Log Daemon ensures that the extension is provided with a complete record of all changes made to content, so that it can take appropriate action.

There are other ways of watching what happens in the Content Store - you can, for example, use event listeners or transaction filters. The Change Log Daemon, however, has a number of advantages:

  • You can write your action or Creating and Using Agents in any language.

  • An agent is completely decoupled from the CUE Content Store, and runs in a separate JVM. If you create more than one agent then each one runs in its own JVM. This makes it easier for your agent to have a different release cycle than the rest of your cluster. You can also restart a malfunctioning agent without affecting the rest of the cluster.

  • It is scalable. One agent puts no more load on the CUE Content Store than a Content Studio user, in some cases less.

  • It follows the principle of doing only one task and doing it well: one Change Log Daemon instance may have only one agent.

  • You don't need to write your own parser and logic to read the change log or follow links or change log pages. All of this is done for you by the Change Log Daemon.

  • Resilience is built in. The Change Log Daemon keeps track of the changes your agent has handled and which agent operations failed, permanently or temporarily, and will always pick up where it left off after a restart.