we will likely need some sort of internal API for these that the rest of the code must use to access options (rather than directly access them via getenv() etc.), so that we can guarantee we have one comprehensive list.

It might even be worthwhile to keep the OCF-like metadata in XML files to be used as the definitive list, with the sysconfig file, ReST files for the books, and C and Python data files created from it automatically via make targets. Alternatively, we could install the XML files, and C and Python APIs could parse them.

Also OCF_RESKEY_trace_dir, if we want to mention that one

For pcmk__designated_controller(), it seems reasonable to just ask the local controller for controld_globals.dc_name, using that as the source of truth instead of broadcasting a ping.

• If it's NULL when there is in fact a DC somewhere, that should be a very temporary state, and "no DC" is still "true" from the local perspective.
• If it's set when the DC has gone offline or something, then similar to above.
• If it's possible for multiple nodes to transiently see themselves as DC, then that already complicates the "ping the DC and wait for a response" approach we use now. There's no obviously correct answer in that case.

All of this stems from dropping the mainloops in pcmk_cluster_queries.c. We replaced them with sync when the timeout is 0 in a6ec43e3. We replaced them with poll when the timeout is greater than 0 in 8771565f. The sync change is causing this problem. It's unclear if the poll change has caused or will cause any problems; that seems less likely, but it's possible.