Interesting post. We wrote this “below” utility [1] that monitor system metrics similar to atop. We want the ability to collect all metrics into a single object, pass it around and visualize it elsewhere. Naturally we need some way to query into fields or even nested-struct fields. For example, to get the file cache usage of a particular process, we need to go through sample->processes->pid->memory->file cache. To do it ergonomically and also type-safely, we end up using proc macro to generate enums that represent field paths of the structs and then use them to query values of non-struct (leaf) fields. I always wonder if there are simpler ways or existing proc macro derives to safe us the efforts. Maybe I do need to look into serde internals for some inspirations.
[1] https://github.com/facebookincubator/below/blob/main/below/b...