[libvirt] virConnectClose() API function question
Hi, as I've been working on libvirt-php I've been able to see that sometimes the virConnectClose() API function is returning the undefined value, like in this example: [2011-06-21 17:29:59 libvirt-php/core]: libvirt_domain_get_info: virDomainGetInfo(0xb3184158) returned 0 [2011-06-21 17:29:59 libvirt-php/core]: Freeing libvirt domain resource at 0x3d9751b3184158 [2011-06-21 17:29:59 libvirt-php/core]: free_resource: virDomainFree(0xb3184158) completed successfully [2011-06-21 17:29:59 libvirt-php/core]: php_libvirt_connection_dtor: virConnectClose(0xb3382588) returned 1 ((null)) [2011-06-21 17:29:59 libvirt-php/core]: check_resource_allocation: libvirt domain resource (conn 0xb3184158) is not allocated In the API reference of libvirt there's an information that it returns 0 or -1 ("0 in case of success or -1 in case of error" as can be seen at [1]) however according to my libvirt-php tests with the debug log enabled there's a return value of 1 with the error string (as caught by libvirt error handler) undefined, i.e. NULL. Does anybody have an idea what may be wrong and why is libvirt sometimes returning undefined value for this function? Thanks, Michal [1] http://libvirt.org/html/libvirt-libvirt.html#virConnectClose -- Michal Novotny <minovotn@redhat.com>, RHCE, Red Hat Virtualization Team (xen userspace) | libvirt-php bindings
2011/6/21 Michal Novotny <minovotn@redhat.com>:
Hi, as I've been working on libvirt-php I've been able to see that sometimes the virConnectClose() API function is returning the undefined value, like in this example:
[2011-06-21 17:29:59 libvirt-php/core]: libvirt_domain_get_info: virDomainGetInfo(0xb3184158) returned 0 [2011-06-21 17:29:59 libvirt-php/core]: Freeing libvirt domain resource at 0x3d9751b3184158 [2011-06-21 17:29:59 libvirt-php/core]: free_resource: virDomainFree(0xb3184158) completed successfully [2011-06-21 17:29:59 libvirt-php/core]: php_libvirt_connection_dtor: virConnectClose(0xb3382588) returned 1 ((null)) [2011-06-21 17:29:59 libvirt-php/core]: check_resource_allocation: libvirt domain resource (conn 0xb3184158) is not allocated
In the API reference of libvirt there's an information that it returns 0 or -1 ("0 in case of success or -1 in case of error" as can be seen at [1]) however according to my libvirt-php tests with the debug log enabled there's a return value of 1 with the error string (as caught by libvirt error handler) undefined, i.e. NULL.
Does anybody have an idea what may be wrong and why is libvirt sometimes returning undefined value for this function?
Thanks, Michal
[1] http://libvirt.org/html/libvirt-libvirt.html#virConnectClose
In contrast to the documentation virConnectClose returns the remaining reference count of the connection after unref'ing it. This means virConnectClose returns -1 on error and returns 0 when there is no reference left and the connection is really closed. When it returns > 0 then the connection isn't closed yet, but is kept open because there are still objects alive that depend on it. For example when you open a connection and get a virDomainPtr from it then the refcount of the connection is increased, because the domain object depends on it. When the domain object is freed then the refcount of the connection is decreased again. All objects in libvirt like connections, domains, networks etc are reference counted. But in contrast to virConnectClose other free functions like virDomainFree don't return the remaining reference count, they really just return -1 or 0. So the question is: do we change virConnectClose to really just return -1 or 0, or do we update the documentation, because someone might depend on virConnectClose allowing to detect via its return value whether the connection was really closed or not. -- Matthias Bolte http://photron.blogspot.com
On 06/21/2011 05:53 PM, Matthias Bolte wrote:
2011/6/21 Michal Novotny <minovotn@redhat.com>:
Hi, as I've been working on libvirt-php I've been able to see that sometimes the virConnectClose() API function is returning the undefined value, like in this example:
[2011-06-21 17:29:59 libvirt-php/core]: libvirt_domain_get_info: virDomainGetInfo(0xb3184158) returned 0 [2011-06-21 17:29:59 libvirt-php/core]: Freeing libvirt domain resource at 0x3d9751b3184158 [2011-06-21 17:29:59 libvirt-php/core]: free_resource: virDomainFree(0xb3184158) completed successfully [2011-06-21 17:29:59 libvirt-php/core]: php_libvirt_connection_dtor: virConnectClose(0xb3382588) returned 1 ((null)) [2011-06-21 17:29:59 libvirt-php/core]: check_resource_allocation: libvirt domain resource (conn 0xb3184158) is not allocated
In the API reference of libvirt there's an information that it returns 0 or -1 ("0 in case of success or -1 in case of error" as can be seen at [1]) however according to my libvirt-php tests with the debug log enabled there's a return value of 1 with the error string (as caught by libvirt error handler) undefined, i.e. NULL.
Does anybody have an idea what may be wrong and why is libvirt sometimes returning undefined value for this function?
Thanks, Michal
[1] http://libvirt.org/html/libvirt-libvirt.html#virConnectClose
In contrast to the documentation virConnectClose returns the remaining reference count of the connection after unref'ing it. This means virConnectClose returns -1 on error and returns 0 when there is no reference left and the connection is really closed. When it returns > 0 then the connection isn't closed yet, but is kept open because there are still objects alive that depend on it. For example when you open a connection and get a virDomainPtr from it then the refcount of the connection is increased, because the domain object depends on it. When the domain object is freed then the refcount of the connection is decreased again.
All objects in libvirt like connections, domains, networks etc are reference counted. But in contrast to virConnectClose other free functions like virDomainFree don't return the remaining reference count, they really just return -1 or 0. So the question is: do we change virConnectClose to really just return -1 or 0, or do we update the documentation, because someone might depend on virConnectClose allowing to detect via its return value whether the connection was really closed or not.
Thanks for the clarification Matthias. Now it makes sense to me ;-) Thanks, Michal -- Michal Novotny <minovotn@redhat.com>, RHCE, Red Hat Virtualization Team (xen userspace) | libvirt-php bindings
On 06/21/2011 09:53 AM, Matthias Bolte wrote:
[1] http://libvirt.org/html/libvirt-libvirt.html#virConnectClose
In contrast to the documentation virConnectClose returns the remaining reference count of the connection after unref'ing it. This means virConnectClose returns -1 on error and returns 0 when there is no reference left and the connection is really closed. When it returns > 0 then the connection isn't closed yet, but is kept open because there are still objects alive that depend on it. For example when you open a connection and get a virDomainPtr from it then the refcount of the connection is increased, because the domain object depends on it. When the domain object is freed then the refcount of the connection is decreased again.
All objects in libvirt like connections, domains, networks etc are reference counted. But in contrast to virConnectClose other free functions like virDomainFree don't return the remaining reference count, they really just return -1 or 0. So the question is: do we change virConnectClose to really just return -1 or 0, or do we update the documentation, because someone might depend on virConnectClose allowing to detect via its return value whether the connection was really closed or not.
At this point, I worry that changing return values might break existing code, so I would favor a documentation update, but I'd also like to hear an opinion from DV or danpb. -- Eric Blake eblake@redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org
On Wed, Jun 22, 2011 at 09:41:57AM -0600, Eric Blake wrote:
On 06/21/2011 09:53 AM, Matthias Bolte wrote:
[1] http://libvirt.org/html/libvirt-libvirt.html#virConnectClose
In contrast to the documentation virConnectClose returns the remaining reference count of the connection after unref'ing it. This means virConnectClose returns -1 on error and returns 0 when there is no reference left and the connection is really closed. When it returns > 0 then the connection isn't closed yet, but is kept open because there are still objects alive that depend on it. For example when you open a connection and get a virDomainPtr from it then the refcount of the connection is increased, because the domain object depends on it. When the domain object is freed then the refcount of the connection is decreased again.
All objects in libvirt like connections, domains, networks etc are reference counted. But in contrast to virConnectClose other free functions like virDomainFree don't return the remaining reference count, they really just return -1 or 0. So the question is: do we change virConnectClose to really just return -1 or 0, or do we update the documentation, because someone might depend on virConnectClose allowing to detect via its return value whether the connection was really closed or not.
At this point, I worry that changing return values might break existing code, so I would favor a documentation update, but I'd also like to hear an opinion from DV or danpb.
I think we shouldn't change the semantics. 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 Wed, Jun 22, 2011 at 04:48:31PM +0100, Daniel P. Berrange wrote:
On Wed, Jun 22, 2011 at 09:41:57AM -0600, Eric Blake wrote:
On 06/21/2011 09:53 AM, Matthias Bolte wrote:
[1] http://libvirt.org/html/libvirt-libvirt.html#virConnectClose
In contrast to the documentation virConnectClose returns the remaining reference count of the connection after unref'ing it. This means virConnectClose returns -1 on error and returns 0 when there is no reference left and the connection is really closed. When it returns > 0 then the connection isn't closed yet, but is kept open because there are still objects alive that depend on it. For example when you open a connection and get a virDomainPtr from it then the refcount of the connection is increased, because the domain object depends on it. When the domain object is freed then the refcount of the connection is decreased again.
All objects in libvirt like connections, domains, networks etc are reference counted. But in contrast to virConnectClose other free functions like virDomainFree don't return the remaining reference count, they really just return -1 or 0. So the question is: do we change virConnectClose to really just return -1 or 0, or do we update the documentation, because someone might depend on virConnectClose allowing to detect via its return value whether the connection was really closed or not.
At this point, I worry that changing return values might break existing code, so I would favor a documentation update, but I'd also like to hear an opinion from DV or danpb.
I think we shouldn't change the semantics.
Just to clarify: The code is right. The docs are wrong. This is actually a good general rule for resolving any doubts :-) 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 06/22/2011 05:57 PM, Daniel P. Berrange wrote:
On Wed, Jun 22, 2011 at 04:48:31PM +0100, Daniel P. Berrange wrote:
On Wed, Jun 22, 2011 at 09:41:57AM -0600, Eric Blake wrote:
On 06/21/2011 09:53 AM, Matthias Bolte wrote:
[1] http://libvirt.org/html/libvirt-libvirt.html#virConnectClose
In contrast to the documentation virConnectClose returns the remaining reference count of the connection after unref'ing it. This means virConnectClose returns -1 on error and returns 0 when there is no reference left and the connection is really closed. When it returns > 0 then the connection isn't closed yet, but is kept open because there are still objects alive that depend on it. For example when you open a connection and get a virDomainPtr from it then the refcount of the connection is increased, because the domain object depends on it. When the domain object is freed then the refcount of the connection is decreased again.
All objects in libvirt like connections, domains, networks etc are reference counted. But in contrast to virConnectClose other free functions like virDomainFree don't return the remaining reference count, they really just return -1 or 0. So the question is: do we change virConnectClose to really just return -1 or 0, or do we update the documentation, because someone might depend on virConnectClose allowing to detect via its return value whether the connection was really closed or not. At this point, I worry that changing return values might break existing code, so I would favor a documentation update, but I'd also like to hear an opinion from DV or danpb. I think we shouldn't change the semantics. Just to clarify: The code is right. The docs are wrong.
This is actually a good general rule for resolving any doubts :-)
Daniel Well, it makes perfect sense to update docs and let user know that there are some resources allocated that has to be freed prior to freeing the connection object so I'm +1 for updating the docs instead ;-)
Michal -- Michal Novotny <minovotn@redhat.com>, RHCE, Red Hat Virtualization Team (xen userspace) | libvirt-php bindings
On Wed, Jun 22, 2011 at 09:41:57AM -0600, Eric Blake wrote:
On 06/21/2011 09:53 AM, Matthias Bolte wrote:
[1] http://libvirt.org/html/libvirt-libvirt.html#virConnectClose
In contrast to the documentation virConnectClose returns the remaining reference count of the connection after unref'ing it. This means virConnectClose returns -1 on error and returns 0 when there is no reference left and the connection is really closed. When it returns > 0 then the connection isn't closed yet, but is kept open because there are still objects alive that depend on it. For example when you open a connection and get a virDomainPtr from it then the refcount of the connection is increased, because the domain object depends on it. When the domain object is freed then the refcount of the connection is decreased again.
All objects in libvirt like connections, domains, networks etc are reference counted. But in contrast to virConnectClose other free functions like virDomainFree don't return the remaining reference count, they really just return -1 or 0. So the question is: do we change virConnectClose to really just return -1 or 0, or do we update the documentation, because someone might depend on virConnectClose allowing to detect via its return value whether the connection was really closed or not.
At this point, I worry that changing return values might break existing code, so I would favor a documentation update, but I'd also like to hear an opinion from DV or danpb.
Agreed, the code has been running taht way forever, this is a documentation bug, let's fix the documentation, Daniel -- Daniel Veillard | libxml Gnome XML XSLT toolkit http://xmlsoft.org/ daniel@veillard.com | Rpmfind RPM search engine http://rpmfind.net/ http://veillard.com/ | virtualization library http://libvirt.org/
participants (5)
-
Daniel P. Berrange -
Daniel Veillard -
Eric Blake -
Matthias Bolte -
Michal Novotny