Libguestfs - Nov 2018 - Re: [collectd] collectd leaks SIGCHLD == SIG_IGN into plugins

I was extending the virt plugin.
It already collects similar data (about VMs) using Libvirt's API, but lacks
disk usage information.

I went through some hoops to link libguestfs correctly to collectd.
Is it okay to just include fork(), waitpid() example? It does reproduce the
issue.

Best Regards,
Peter


On Tue, Nov 13, 2018 at 1:34 PM Richard W.M. Jones <rjones@redhat.com>
wrote:
> On Tue, Nov 13, 2018 at 12:00:19PM +0100, Florian Forster wrote:
> > Hi,
> >
> > thank you very much for reporting this! Sounds like a bug in the exec
> plugin –
> > it never ceases to amaze me how many issues a single plugin can have
;)
> >
> > > > > This means that any plugin that does the usual pattern
of:
> > > > >
> > > > >   pid = fork ();
> >
> > Note that the exec plugin is the *only* plugin that does this. All
other
> > plugins are forbidden to fork(), popen() or create new processes in
any
> other
> > way. The only plugin doing that, the exec plugin, has had enough
issues
> over
> > the years for me to feel justified in that decision. ;-)
> >
> > As mentioned before, a Github issue would be appreciated so we can
> properly
> > track this problem.
>
> I don't know if Peter is using the exec plugin or is trying to write
> an ordinary plugin.  However the library he is using (libguestfs)
> certainly does fork subprocess(es).
>
> Rich.
>
> --
> Richard Jones, Virtualization Group, Red Hat
> http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> virt-builder quickly builds VMs from scratch
> http://libguestfs.org/virt-builder.1.html
>

On Tue, Nov 13, 2018 at 03:17:33PM +0200, Peter Dimitrov
wrote:
> I was extending the virt plugin.
> It already collects similar data (about VMs) using Libvirt's API, but
lacks
> disk usage information.
> 
> I went through some hoops to link libguestfs correctly to collectd.
> Is it okay to just include fork(), waitpid() example? It does reproduce the
> issue.
Yes, I think a small example/reproducer is a fine idea.

Rich.
> Best Regards,
> Peter
> 
> 
> On Tue, Nov 13, 2018 at 1:34 PM Richard W.M. Jones
<rjones@redhat.com>
> wrote:
> 
> > On Tue, Nov 13, 2018 at 12:00:19PM +0100, Florian Forster wrote:
> > > Hi,
> > >
> > > thank you very much for reporting this! Sounds like a bug in the
exec
> > plugin –
> > > it never ceases to amaze me how many issues a single plugin can
have ;)
> > >
> > > > > > This means that any plugin that does the usual
pattern of:
> > > > > >
> > > > > >   pid = fork ();
> > >
> > > Note that the exec plugin is the *only* plugin that does this.
All other
> > > plugins are forbidden to fork(), popen() or create new processes
in any
> > other
> > > way. The only plugin doing that, the exec plugin, has had enough
issues
> > over
> > > the years for me to feel justified in that decision. ;-)
> > >
> > > As mentioned before, a Github issue would be appreciated so we
can
> > properly
> > > track this problem.
> >
> > I don't know if Peter is using the exec plugin or is trying to
write
> > an ordinary plugin.  However the library he is using (libguestfs)
> > certainly does fork subprocess(es).
> >
> > Rich.
> >
> > --
> > Richard Jones, Virtualization Group, Red Hat
> > http://people.redhat.com/~rjones
> > Read my programming and virtualization blog: http://rwmj.wordpress.com
> > virt-builder quickly builds VMs from scratch
> > http://libguestfs.org/virt-builder.1.html
> >
-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org

Github issue is a fact.
https://github.com/collectd/collectd/issues/2993

Best Regards,
Peter


On Tue, Nov 13, 2018 at 3:28 PM Richard W.M. Jones <rjones@redhat.com>
wrote:
> On Tue, Nov 13, 2018 at 03:17:33PM +0200, Peter Dimitrov wrote:
> > I was extending the virt plugin.
> > It already collects similar data (about VMs) using Libvirt's API,
but
> lacks
> > disk usage information.
> >
> > I went through some hoops to link libguestfs correctly to collectd.
> > Is it okay to just include fork(), waitpid() example? It does
reproduce
> the
> > issue.
>
> Yes, I think a small example/reproducer is a fine idea.
>
> Rich.
>
> > Best Regards,
> > Peter
> >
> >
> > On Tue, Nov 13, 2018 at 1:34 PM Richard W.M. Jones
<rjones@redhat.com>
> > wrote:
> >
> > > On Tue, Nov 13, 2018 at 12:00:19PM +0100, Florian Forster wrote:
> > > > Hi,
> > > >
> > > > thank you very much for reporting this! Sounds like a bug in
the exec
> > > plugin –
> > > > it never ceases to amaze me how many issues a single plugin
can have
> ;)
> > > >
> > > > > > > This means that any plugin that does the
usual pattern of:
> > > > > > >
> > > > > > >   pid = fork ();
> > > >
> > > > Note that the exec plugin is the *only* plugin that does
this. All
> other
> > > > plugins are forbidden to fork(), popen() or create new
processes in
> any
> > > other
> > > > way. The only plugin doing that, the exec plugin, has had
enough
> issues
> > > over
> > > > the years for me to feel justified in that decision. ;-)
> > > >
> > > > As mentioned before, a Github issue would be appreciated so
we can
> > > properly
> > > > track this problem.
> > >
> > > I don't know if Peter is using the exec plugin or is trying
to write
> > > an ordinary plugin.  However the library he is using (libguestfs)
> > > certainly does fork subprocess(es).
> > >
> > > Rich.
> > >
> > > --
> > > Richard Jones, Virtualization Group, Red Hat
> > > http://people.redhat.com/~rjones
> > > Read my programming and virtualization blog:
http://rwmj.wordpress.com
> > > virt-builder quickly builds VMs from scratch
> > > http://libguestfs.org/virt-builder.1.html
> > >
>
> --
> Richard Jones, Virtualization Group, Red Hat
> http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> libguestfs lets you edit virtual machines.  Supports shell scripting,
> bindings from many languages.  http://libguestfs.org
>