Logging

A useful logging design starts with a question precise enough to become a query. “Show errors” is different from “How many checkout requests finally failed between ten and eleven UTC?” The first locates diagnostic events. The second needs a population of completed requests, a definition of failure, and a time rule. Collecting more text does not supply these missing semantics automatically. ...

Log rotation divides a continuing stream into files that can be retained, searched, compressed, and eventually removed. A useful policy defines both when to rotate and which history to keep. It must also account for how the application holds its output file open. Renaming a pathname and successfully redirecting future log records are separate steps in that operational contract. ...