[libvirt-users] libvirt: XML-RPC error : Cannot write data: Broken pipe
Hi all, I think it's a bug, when call virDomainGetState after "service libvirtd stop", I receive signal SIGPIPE. I want to know how to avoid this problem? And Other interfaces will also encounter this problem？ Below the bt information: Below some information about my hypervisor: root@ubuntu-05:/datapool/zhuohf# virsh -v 3.4.0 root@ubuntu-05:/datapool/zhuohf# qemu-x86_64 -version qemu-x86_64 version 2.9.0 Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers
On Wed, Aug 09, 2017 at 11:53:54AM +0800, netsurfed wrote:
Hi all, I think it's a bug, when call virDomainGetState after "service libvirtd stop" , I receive signal SIGPIPE.
For the QEMU driver, the libvirt library just talks to libvirtd over an RPC layer. You killed libvirtd, so the libvirt library gets SIGPIPE.
I want to know how to avoid this problem? And Other interfaces will also
If you want libvirt to work, don't stop libvirtd Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
The error message could however give a hint what is going on. It should sax that it is impossible to talk to libvirtd and that it might be stopped. On 9 Aug 2017 2:19 p.m., "Daniel P. Berrange" <berrange@redhat.com> wrote:
On Wed, Aug 09, 2017 at 11:53:54AM +0800, netsurfed wrote:
Hi all, I think it's a bug, when call virDomainGetState after "service libvirtd stop" , I receive signal SIGPIPE.
For the QEMU driver, the libvirt library just talks to libvirtd over an RPC layer. You killed libvirtd, so the libvirt library gets SIGPIPE.
I want to know how to avoid this problem? And Other interfaces will also
If you want libvirt to work, don't stop libvirtd
Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/ dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/ dberrange :|
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On 08/09/2017 03:59 PM, Dominik Psenner wrote:
The error message could however give a hint what is going on. It should sax that it is impossible to talk to libvirtd and that it might be stopped.
[Please don't top post on technical lists] Yes and no. There can be a lot of reasons why client can't talk to daemon. They all don't demonstrate in local connection, but imagine talking to a daemon on distant host. And suddenly somebody cuts the cable, or inserts incorrect firewall rules, etc. Suggesting that daemon is not running would be wrong in this case. Also, we tend to report system errors and leave mgmt application figure out how to deal with it. For instance: http://libvirt.org/git/?p=libvirt.git;a=blob;f=tools/virsh.c;h=94bb7ff6c93af... Michal
2017-08-10 8:21 GMT+02:00 Michal Privoznik <mprivozn@redhat.com>:
On 08/09/2017 03:59 PM, Dominik Psenner wrote:
The error message could however give a hint what is going on. It should sax that it is impossible to talk to libvirtd and that it might be stopped.
[Please don't top post on technical lists]
Yes and no. There can be a lot of reasons why client can't talk to daemon. They all don't demonstrate in local connection, but imagine talking to a daemon on distant host.
And suddenly somebody cuts the
cable, or inserts incorrect firewall rules, etc. Suggesting that daemon is not running would be wrong in this case.
Actually, it would most probably be true in this case and still the most probable cause if the communication went over a wire. Yes, it could be a firewall issue but still it is more likely that the host or the service is not up.
Also, we tend to report system errors and leave mgmt application figure out how to deal with it. For instance:
http://libvirt.org/git/?p=libvirt.git;a=blob;f=tools/virsh.c;h= 94bb7ff6c93afa46d31d085eaa5e504f1cca7593;hb=HEAD#l90
Are you indicating that a user should have to read the sourcecode of libvirt and libvirtd to understand their error messages? Please bear in mind that we are humans that use a software and as such the software should be written to be used by humans. I know very well that good error handling is a tough task to achieve, but it is still worth the effort. I suggest that the error message: libvirt: XML-RPC error : Cannot write data: Broken pipe should read as: libvirt: Could not connect to the libvirtd service : Cannot write data: Broken pipe The first indicates that there's an XML-RPC error going on. To a user this sounds like a bad problem that he cannot solve by himself. Maybe it is an incompatible API or the connection broke while transferring data or the connection crashed, maybe trying to send something that shouldn't be sent with XML-RPC. Anyway it doesn't give a clue to a user that does not know how libvirt and libvirtd work internally. The latter is much clearer in explaining that there's a connectivity issue and that it could not even open the connection to the service. On top of that it includes the actual cause, namely a broken pipe. Cheers -- Dominik Psenner
On 08/10/2017 10:45 AM, Dominik Psenner wrote:
2017-08-10 8:21 GMT+02:00 Michal Privoznik <mprivozn@redhat.com>:
On 08/09/2017 03:59 PM, Dominik Psenner wrote:
The error message could however give a hint what is going on. It should sax that it is impossible to talk to libvirtd and that it might be stopped.
[Please don't top post on technical lists]
Yes and no. There can be a lot of reasons why client can't talk to daemon. They all don't demonstrate in local connection, but imagine talking to a daemon on distant host.
And suddenly somebody cuts the
cable, or inserts incorrect firewall rules, etc. Suggesting that daemon is not running would be wrong in this case.
Actually, it would most probably be true in this case and still the most probable cause if the communication went over a wire. Yes, it could be a firewall issue but still it is more likely that the host or the service is not up.
Also, we tend to report system errors and leave mgmt application figure out how to deal with it. For instance:
http://libvirt.org/git/?p=libvirt.git;a=blob;f=tools/virsh.c;h= 94bb7ff6c93afa46d31d085eaa5e504f1cca7593;hb=HEAD#l90
Are you indicating that a user should have to read the sourcecode of libvirt and libvirtd to understand their error messages?
No, I'm indicating that you should read the documentation. What I gave you was a usage example.
Please bear in mind that we are humans that use a software and as such the software should be written to be used by humans. I know very well that good error handling is a tough task to achieve, but it is still worth the effort. I suggest that the error message:
libvirt: XML-RPC error : Cannot write data: Broken pipe
Again, after reading corresponding documentation you'll find that: XML-RPC error stands for error.domain = VIR_FROM_RPC, and to change "XML-RPC" to something else we would need yet another domain. It would be wrong anyway - the domain of the error is RPC code after all.
should read as:
libvirt: Could not connect to the libvirtd service : Cannot write data: Broken pipe
This is untrue. You are connected at this point, otherwise you wouldn't be able to get the domain object you are passing to the API in the first place. Only by writing to the connection socket you learn (well, the code) that the daemon is gone. That's why we have keep alive, connection close callbacks and all these fancy features that help you to learn this fact sooner, without having to call any APIs. Moreover, they can take actions once the connection gets disconnected. But I'm not going to link any more code to not discourage you. Michal
On Thu, Aug 10, 2017 at 10:45:49AM +0200, Dominik Psenner wrote:
2017-08-10 8:21 GMT+02:00 Michal Privoznik <mprivozn@redhat.com>:
On 08/09/2017 03:59 PM, Dominik Psenner wrote:
The error message could however give a hint what is going on. It should sax that it is impossible to talk to libvirtd and that it might be stopped.
[Please don't top post on technical lists]
Yes and no. There can be a lot of reasons why client can't talk to daemon. They all don't demonstrate in local connection, but imagine talking to a daemon on distant host.
And suddenly somebody cuts the
cable, or inserts incorrect firewall rules, etc. Suggesting that daemon is not running would be wrong in this case.
Actually, it would most probably be true in this case and still the most probable cause if the communication went over a wire. Yes, it could be a firewall issue but still it is more likely that the host or the service is not up.
Also, we tend to report system errors and leave mgmt application figure out how to deal with it. For instance:
http://libvirt.org/git/?p=libvirt.git;a=blob;f=tools/virsh.c;h= 94bb7ff6c93afa46d31d085eaa5e504f1cca7593;hb=HEAD#l90
Are you indicating that a user should have to read the sourcecode of libvirt and libvirtd to understand their error messages? Please bear in mind that we are humans that use a software and as such the software should be written to be used by humans. I know very well that good error handling is a tough task to achieve, but it is still worth the effort. I suggest that the error message:
libvirt: XML-RPC error : Cannot write data: Broken pipe
should read as:
libvirt: Could not connect to the libvirtd service : Cannot write data: Broken pipe
The code in question is used to communicate with *faaar* more than just libvirtd, so such a change would be pretty misleading in general. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
participants (4)
-
Daniel P. Berrange -
Dominik Psenner -
Michal Privoznik -
netsurfed