On Fri, Jul 14, 2017 at 7:23 AM, John Spray <jspray@xxxxxxxxxx> wrote: > Hi all, > > There's a change headed for master soon > (https://github.com/ceph/ceph/pull/16211) that will rework how config > settings are declared. Currently they're declared using a > preprocessor macro, which is a bit too inflexible for some desirable > enhancements like having different defaults for clients vs servers, > adding more bounds/range checking, and adding more descriptive doc > metadata. > > The thing that will effect you immediately is how to add new config settings: > - Add them in common/options.cc > - Access them using md_config_t::get() > > The old-style definitions for existing settings still exist in > common/legacy_config_opts.h. Do *not* add new definitions to that > file. All the definitions in that file now have equivalent > definitions in common/options.cc, and the ones in common/options.cc > are authoritative. > > The old header lives on in order to generate C++ member definitions > for the options in md_config_t (i.e. so that you can get at them with > g_conf->my_config_opt). Once the consuming code has been modified to > avoid accessing them that way, the entries from legacy_config_opts.h > can be removed. > > This sacrifices the compile-time check that you would previously get > by accessing a class member. Aww, that's disappointing. Maybe of limited value, but if we ever typo one of those options it's going to be rough to track down. What kind of runtime checking is available? Could we maybe do something like generate wrapper functions so each config value we know about at compile time has a getter function we can invoke instead of get(<string>)? > The benefit is that we can do all the > new-style stuff with clean C++, that we can in principle load > definitions at runtime (e.g. from the planned central mon config > store), and that md_config_t will now know which options are really in > use (because they're accessed by function and not by direct member > access). > > John > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
