Philip Martin wrote on Fri, May 31, 2013 at 14:23:35 +0100: > Daniel Shahaf <danie...@apache.org> writes: > > > On Fri, May 31, 2013 at 01:35:57PM +0100, Philip Martin wrote: > >> I think something like that would work but I'm unsure whether we should > >> provide it. I'm concerned that it would be making freeze special. > >> Would we need to provide similar queries for upgrade, recover, pack, > >> etc? > >> > > > > For what it's worth: > > > > I wanted to add "Is a write-lock being held?" to 'svnadmin info'. That was > > just on a hunch that it might be useful --- I didn't have a concrete > > use-case > > (and that feature has not been implemented). > > I guess that would be implemented by a non-blocking attempt to get a > lock. Occasionally it would see a commit holding a lock as well as the > other longer running commands. I can't decide whether queries like > that, or the freeze query, are useful. > > >> A timeout leads on to a question was about error handling. At present > >> the return value of "svnadmin freeze repository program" is the return > >> value of the external program provided freeze managed to run the > >> program. If freeze failed to run the program for some reason then the > >> return value is generated by svnadmin directly. There is no way to > >> distinguish errors from 'program' from errors from 'svnadmin', they both > >> return values in the range 0-255. Success, zero, is unambiguous but any > >> error is difficult to interpret. > >> > >> I don't see any easy way round this. If we stop providing the 'program' > >> error as the return value how else do we provide it? > > > > IIRC, some applications use the following strategy: "If execvp() failed, > > exit 126; else, exit with the child's exit code (possibly zero)". > > > > Sorry, I don't remember which man page I saw that strategy in. > > At present a failed exec returns 255 (on my machine). The problem is > that the external program can also return 255. If we document a value > then callers know it is possible that exec failed but can't be sure. >
Can't we just ask people who really care about all 8 bits of the child's exit code to use the bindings? > >> Invoke some post-freeze command and pass it as a parameter? > > > > I suppose the post-freeze command should be optional? > > I think so but I'm not sure how, or even if, it would work. Would we > simply have the the same problem of how to return the post-freeze > command status? We'd have the failure mode that the freeze-hook failed to run (or ran and exited non-zero). Callers also have to handle the failure mode whereby 'svnadmin' itself didn't exist (which goes back to your "failed exec reports 255" above).
