The default behaviour of the Integration Server is to allow all of the available thread pool to be used for processing published documents. This is not advised for production environments.

To engage the "throttling" ability of the Integration server, go into the web admin UI, to "settings", "resources", "trigger throttle controls", "Edit trigger throttle controls" and set to a value less than 100% (the default).

This will mean that only a percentage of the available execution threads will be taken up in the event of a huge backlog of documents in the broker queues.