patch 1/2 debuginfod client
Frank Ch. Eigler
Mon Nov 18 20:33:00 GMT 2019
> > > But since the user won't see the URL generated they might not notice
> > > what is really going on. They will just see that something wasn't
> > > found, won't they?
> > Yes, so the only benefit would be the generation of a different error
> > message for impossible buildids.
> But if there are multiple server URLs it might not be clear which/where
> the error came from.
(My comment was about detecting even number of chars in the hex code.)
> Since all this is done through a very simple web
> api I think it is useful for the user to get informed about what the
> actual request URL was that failed. [...]
> If we go with the client connection context idea for the API we could
> add an extra function that would tell you the last URL tried maybe?
Yeah, maybe. They are tried in parallel. We could also hook up to
libcurl's own progress-notification callbacks.
> > > Do you know how other libraries that use libcurl deal with this?
> > I looked over some other libcurl users in fedora. Some don't worry
> > about the issue at all, relying on implicit initialization, which is
> > only safe if single-threaded. Others (libvirtd) do an explicitly
> > invoked initialization function, which is also only safe if invoked
> > from a single-threaded context.
> > I think actually our way here, running the init function from the
> > shared library constructor, is about the best possible. As long as
> > the ld.so process is done as normal, it should be fine. Programs that
> > use the elfutils trick of manual dlopen'ing libdebuginfod.so should do
> > so only if they are single-threaded.
> But they cannot really control that... Since they might not know (and
> really shouldn't care) that libdw lazily tries to dlopen
> libdebuginfod.so which then pulls in libcurl and calls that global init
> Could we do try to do the dlopen and global curl initialization from
> libdw _init, or a ctor, to make sure it is done as early as possible?
Doing a redundant initialization later is not a problem; there is a
counter in there. The problematic case would be
- a multithreaded application
- loading debuginfod.so multiply concurrently somehow
- and calling the solib ctor concurrently somehow
- and all of this concurrently enough to defeat libcurl's init-counter
IMHO, not worth worrying about. Someday libcurl will do the right
thing (tm) and plop this initialization into their solib ctor.
> > > I was more thinking zero == infinity (no timeout).
> > An unset environment variable should do that.
> Are you sure? If DEBUGINFOD_TIMEOUT isn't set, then it seems it
> defaults to 5 seconds:
> /* Timeout for debuginfods, in seconds.
> This env var must be set for debuginfod-client to run. */
> static const char *server_timeout_envvar = DEBUGINFOD_TIMEOUT_ENV_VAR;
> static int server_timeout = 5;
> if (getenv(server_timeout_envvar))
> server_timeout = atoi (getenv(server_timeout_envvar));
OK, hm, we could make an -empty- but set environment variable mean
'infinity'. Then again, a user can also say =99999.
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