[libvirt] How to suppress error printing to stderr from virConnectOpen*?
I can set the global error handling function (virSetErrorFunc). That doesn't seem to be a good idea from a library. Looking at the code, it doesn't appear that the internal virErrorHandler is thread-local, so I can't set it and restore it around the function call. I can set the error handling function _after_ I've got a connection object (virConnSetErrorFunc). That doesn't help with making the initial connection. libguestfs itself has the same problem with the guestfs_create call, so I'm not going to point any fingers :-) However it seems like a shortcoming of the libvirt API. Am I missing something here? Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones New in Fedora 11: Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 70 libraries supprt'd http://fedoraproject.org/wiki/MinGW http://www.annexia.org/fedora_mingw
On Fri, May 06, 2011 at 05:43:41PM +0100, Richard W.M. Jones wrote:
I can set the global error handling function (virSetErrorFunc). That doesn't seem to be a good idea from a library. Looking at the code, it doesn't appear that the internal virErrorHandler is thread-local, so I can't set it and restore it around the function call.
I can set the error handling function _after_ I've got a connection object (virConnSetErrorFunc). That doesn't help with making the initial connection.
libguestfs itself has the same problem with the guestfs_create call, so I'm not going to point any fingers :-) However it seems like a shortcoming of the libvirt API.
Am I missing something here?
Not really. I really consider the default error printing function itself to be a flawed idea as a library shouldn't print to stderr by default. I'm really torn on whether we can change it though, since although most apps disable it, some may be relying on it. Perhaps adding a flag to virConnectOpenAuth(), VIR_CONNECT_NOP_ERROR_FUNC but not sure how practical that is to actually implement in our internal error handling infrastructure. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
On Mon, May 09, 2011 at 10:32:10AM +0100, Daniel P. Berrange wrote:
On Fri, May 06, 2011 at 05:43:41PM +0100, Richard W.M. Jones wrote:
I can set the global error handling function (virSetErrorFunc). That doesn't seem to be a good idea from a library. Looking at the code, it doesn't appear that the internal virErrorHandler is thread-local, so I can't set it and restore it around the function call.
I can set the error handling function _after_ I've got a connection object (virConnSetErrorFunc). That doesn't help with making the initial connection.
libguestfs itself has the same problem with the guestfs_create call, so I'm not going to point any fingers :-) However it seems like a shortcoming of the libvirt API.
Am I missing something here?
Not really. I really consider the default error printing function itself to be a flawed idea as a library shouldn't print to stderr by default. I'm really torn on whether we can change it though, since although most apps disable it, some may be relying on it.
Perhaps adding a flag to virConnectOpenAuth(), VIR_CONNECT_NOP_ERROR_FUNC but not sure how practical that is to actually implement in our internal error handling infrastructure.
Is there a way to add / make the default error function be thread local? As long as I can null it out around the call safely (without affecting other threads) then that fixes it for me. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://et.redhat.com/~rjones/virt-df/
participants (2)
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Daniel P. Berrange -
Richard W.M. Jones