1. A computer-implemented method for processing data, in which a computer system performs operations comprising: identifying a processing pipeline defining a series of markup language processing steps including receiving a selection of a markup language processing service for which debugging is to be enabled, the selected markup language processing service defining a respective processing pipeline of markup language processing steps; inserting at least one debugging step into the processing pipeline, the at least one debugging step defining processing to collect debug data associated with application of the markup language processing steps to markup language data to be processed by the processing pipeline including identifying a configuration associated with the selected markup language processing service for which debugging is to be enabled; for each markup language processing step defined in the configuration, inserting a debug step into the configuration, the debug step capturing a snapshot of debug data associated with that markup language processing step; and executing the series of markup language processing steps, including the at least one debugging step, upon input markup language data as a transaction, execution of the at least one debugging step capturing the debug data for at least one of the series of markup language processing steps in the processing pipeline, the debug data allowing analysis of operation of the markup language processing steps of the processing pipeline on the input markup language data, wherein executing the series of markup language processing steps, including the at least one debugging step, upon input markup language data as a transaction comprises: detecting a trigger event during processing of a transaction and in response, indicating that the debug data collected from execution of the debug steps associated with the transaction is to be post-processed and not discarded.