Request to add a file index offset to PostCloseFileRenamer
In some of the recent testing at protoDUNE, we were excited to see the successful stopping and recovery of an artdaq data logging process1 during a data-taking run. One issue that I noted was that when the logging process was re-introduced to the running system, the file index in the raw data filename restarted counting at one. In thinking ahead to artdaq-based systems that will want to restart crashed data logger processes and avoid over-writing existing raw data files with low-number file indexes, it seems worthwhile to add the ability to specify an initial offset in the PostCloseFileRenamer. Code within the artdaq system will be responsible for determining the appropriate offset and telling the PostCloseFileRenamer instance(s) about it, so the request that I'm making here is simply to add the ability to specify an offset to the PostCloseFileRenamer class. I'll attach candidate code changes to this Issue (based on the class as it existed in art v2_10_02).
1 This is mainly trivia, but I wanted to point out that I was deliberately vague in my description of a 'data logger process' at protoDUNE. It turns out that we log data from EventBuilder processes in the protoDUNE DAQ, instead of using artdaq DataLogger processes to do that. The elimination of the DataLogger layer at protoDUNE saved a little bit of data transfer and system complication, so it was deemed worthwhile. But that doesn't change the substance of this request. Independent of where we do data logging in an artdaq system, we would like the ability to recover a crashed process and avoid over-writing existing files.