XML Collectd: XML collectd threads still trying after node deletion

The handling of the deletion of nodes and/or interfaces is performed by Collectd, not the collector implementations. It is Collectd the responsible for managing the collection scheduler (not the implementations). Now, when you remove a node or an interface related with data collection, Collectd will remove the IP from its cache, and it won't schedule data collection anymore for that IP. But, if there is already a collection request on the scheduler's queue, that will be executed, and the consequence is what you're seeing on the logs. Of course the exception thrown will be different on each collector implementation. In theory, this kind of exception should not appear more than once after removing the node/interface. With this in mind, have you checked if this is the case ?