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From: "Frank Ch. Eigler" <fche@redhat.com>
To: Mark Wielaard <mark@klomp.org>
Cc: elfutils-devel@sourceware.org, amerey@redhat.com
Subject: Re: patch 1/2 debuginfod client
Date: Mon, 18 Nov 2019 20:33:00 -0000	[thread overview]
Message-ID: <20191118203324.GD2880@redhat.com> (raw)
In-Reply-To: <356e88e4937ddb97a3e7cc93dbdfe29239ff960e.camel@klomp.org>

Hi -

> > > 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
> function...
> 
> 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.

- FChE

  reply	other threads:[~2019-11-18 20:33 UTC|newest]

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-28 19:04 patch 0/2 debuginfod submission Frank Ch. Eigler
2019-10-28 19:06 ` patch 1/2 debuginfod client Frank Ch. Eigler
2019-10-28 19:09   ` patch 2/2 debuginfod server etc Frank Ch. Eigler
2019-11-04 21:48     ` patch 3/3 debuginfod client interruptability Frank Ch. Eigler
2019-11-07  9:07       ` patch 4 debuginfod: symlink following mode Frank Ch. Eigler
2019-11-07  9:08         ` patch 5 debuginfod: prometheus metrics Frank Ch. Eigler
2019-11-15 17:26           ` Mark Wielaard
2019-11-15 17:58             ` Frank Ch. Eigler
2019-11-18 16:20               ` Mark Wielaard
2019-11-18 16:48                 ` Frank Ch. Eigler
2019-11-19 16:13                   ` Mark Wielaard
2019-11-15 16:49         ` patch 4 debuginfod: symlink following mode Mark Wielaard
2019-11-15 18:31           ` Frank Ch. Eigler
2019-11-18 16:27             ` Mark Wielaard
2019-11-15 16:16       ` patch 3/3 debuginfod client interruptability Mark Wielaard
2019-11-15 17:03         ` Aaron Merey
2019-11-15 17:35           ` Mark Wielaard
2019-11-15 18:14             ` Pedro Alves
2019-11-17 23:44               ` Mark Wielaard
2019-11-18  2:50                 ` Frank Ch. Eigler
2019-11-18  9:24                   ` Pedro Alves
2019-11-19 12:58                   ` Mark Wielaard
2019-11-13 17:22     ` patch 2/2 debuginfod server etc Mark Wielaard
2019-11-14 11:54       ` Frank Ch. Eigler
2019-11-16  1:31         ` Mark Wielaard
2019-11-13 23:19     ` Mark Wielaard
2019-11-14 12:30       ` Frank Ch. Eigler
2019-11-18 14:17         ` Mark Wielaard
2019-11-18 18:41           ` Frank Ch. Eigler
2019-11-19 15:41             ` Mark Wielaard
2019-11-19 16:13               ` Frank Ch. Eigler
2019-11-19 20:11                 ` Mark Wielaard
2019-11-19 21:15                   ` Frank Ch. Eigler
2019-11-20 11:53                     ` Mark Wielaard
2019-11-20 12:29                       ` Frank Ch. Eigler
2019-11-21 14:16                       ` Mark Wielaard
2019-11-21 15:40                         ` Mark Wielaard
2019-11-21 16:01                           ` Frank Ch. Eigler
2019-11-21 15:58                         ` Frank Ch. Eigler
2019-11-21 16:37                           ` Mark Wielaard
2019-11-21 17:18                             ` Frank Ch. Eigler
2019-11-21 20:42                               ` Mark Wielaard
2019-11-22 12:08                                 ` Mark Wielaard
2019-11-14 20:45     ` Mark Wielaard
2019-11-15 11:03       ` Mark Wielaard
2019-11-15 21:00       ` Frank Ch. Eigler
2019-11-18 15:01         ` Mark Wielaard
2019-11-15 14:40     ` Mark Wielaard
2019-11-15 19:54       ` Frank Ch. Eigler
2019-11-18 15:31         ` Mark Wielaard
2019-11-18 15:49           ` Frank Ch. Eigler
2019-11-12 11:12   ` patch 1/2 debuginfod client Mark Wielaard
2019-11-12 15:14     ` Frank Ch. Eigler
2019-11-12 21:59       ` Mark Wielaard
2019-11-14  0:33         ` Frank Ch. Eigler
2019-11-15 21:33       ` Mark Wielaard
2019-11-12 21:25   ` Mark Wielaard
2019-11-13 23:25     ` Frank Ch. Eigler
2019-11-16  0:46       ` Mark Wielaard
2019-11-16 18:53         ` Frank Ch. Eigler
2019-11-18 17:17           ` Mark Wielaard
2019-11-18 20:33             ` Frank Ch. Eigler [this message]
2019-11-19 15:57               ` Mark Wielaard
2019-11-19 16:20                 ` Frank Ch. Eigler
2019-11-19 20:16                   ` Mark Wielaard
2019-11-19 21:22                     ` Frank Ch. Eigler
2019-11-20 12:50                       ` Mark Wielaard
2019-11-20 13:30                         ` Frank Ch. Eigler
2019-11-21 14:02                           ` Mark Wielaard
2019-11-13 13:57   ` Mark Wielaard
2019-11-14 11:24     ` Frank Ch. Eigler
2019-11-16  0:52       ` Mark Wielaard
2019-11-16  2:28         ` Frank Ch. Eigler
2019-10-30 11:04 ` patch 0/2 debuginfod submission Mark Wielaard
2019-10-30 13:40   ` Frank Ch. Eigler
2019-10-30 14:12     ` Mark Wielaard
2019-10-30 18:11       ` Frank Ch. Eigler
2019-10-31 11:18         ` Mark Wielaard

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