A diagnostic extract is a log file portion from a job step, typically describing an error or interesting condition, extracted by a postprocessor and saved for reporting. The postprocessor usually places this information in an XML file in the top-level job workspace directory, and then sets a property that contains the file name. The CloudBees CD/RO postp postprocessor uses file names like
diag-2770.xml, where "2770" is the unique identifier for the step. Other postprocessors you may use can have a different file name configuration.