10:57 a.m.
Howdy,
I'm about to checkin some XML-RPC code into CVS. The code I'm checking
in won't compile by default (for now) as there's still a little work to
do but I wanted to get something into the tree. Here are the tasks left:
1) Convert from dict to s-expressions to handle config returns. Right
now, the Xend XML-RPC code returns S-Expressions in the form of a
tuple. We just need a little code to convert from these tuples to
struct sexpr's.
2) Integrate my unit tests. I've got a number of unit tests that stress
the various bits of parsing code. I'd like to add a make check that
runs these unit tests and a make fullcheck that runs these unit tests
under valgrind.
3) Support XML-RPC over a domain socket. Right now I'm using nanohttp
which doesn't appear to allow different transports. There is some HTTP
PUT code already in the tree so I could use that if there isn't a more
clever solution.
4) Plumb the xend backend functions to XML-RPC. This is really straight
forward. It's just a matter of converting:
int
xend_pause(virConnectPtr xend, const char *name)
{
return xend_op(xend, name, "op", "pause", NULL);
}
To:
int
xend_pause(virConnectPtr xend, const char *name)
{
if (xend->xmlrpc)
return xmlRpcCall(xend->xmlrpc, "xend.domain.pause", "",
"s", name)
else
return xend_op(xend, name, "op", "pause", NULL);
}
Of course, using the xml-rpc code, we now have access to rich fault
information. Xend never actually returns errors for things and instead
throws exceptions. For the S-Expression/HTTP protocol, you just get a
501 and have to return a meaningless error. With XML-RPC, those
exceptions are actually serialized and sent over the wire. We may want
to explore how we can make that information available to the user.
My current understanding, btw, is that the basic XML-RPC support for
Xend is going into the tree sometime this week (Ewan is looking at the
code now) and will be a part of the 3.0.2 release. This means that for
the 3.0.3 cycle, we'll be defining a standard API. This process will be
starting soon (within the next couple of weeks hopefully).
Regards,
Anthony Liguori
4:21 p.m.
On Fri, Mar 10, 2006 at 10:57:59AM -0600, Anthony Liguori wrote:
Howdy,
Evening ;-)
I'm about to checkin some XML-RPC code into CVS. The code
I'm checking
okay got it. Please add a Changelog entry when you commit to the base :-)
in won't compile by default (for now) as there's still a
little work to
do but I wanted to get something into the tree. Here are the tasks left:
1) Convert from dict to s-expressions to handle config returns. Right
now, the Xend XML-RPC code returns S-Expressions in the form of a
tuple. We just need a little code to convert from these tuples to
struct sexpr's.
2) Integrate my unit tests. I've got a number of unit tests that stress
the various bits of parsing code. I'd like to add a make check that
runs these unit tests and a make fullcheck that runs these unit tests
under valgrind.
3) Support XML-RPC over a domain socket. Right now I'm using nanohttp
which doesn't appear to allow different transports. There is some HTTP
PUT code already in the tree so I could use that if there isn't a more
clever solution.
4) Plumb the xend backend functions to XML-RPC. This is really straight
forward. It's just a matter of converting:
int
xend_pause(virConnectPtr xend, const char *name)
{
return xend_op(xend, name, "op", "pause", NULL);
}
To:
int
xend_pause(virConnectPtr xend, const char *name)
{
if (xend->xmlrpc)
return xmlRpcCall(xend->xmlrpc, "xend.domain.pause", "",
"s", name)
else
return xend_op(xend, name, "op", "pause", NULL);
}
Okay the steps needed look fairly clear, thanks :-)
Of course, using the xml-rpc code, we now have access to rich fault
information. Xend never actually returns errors for things and instead
throws exceptions.
the new error code tries at least to extract the error message when
an HTTP POST or GEt fails with an error code, but the XML-RPC should
give a far more reliable framework for error handling.
For the S-Expression/HTTP protocol, you just get a
501 and have to return a meaningless error. With XML-RPC, those
exceptions are actually serialized and sent over the wire. We may want
to explore how we can make that information available to the user.
I would say as a buffer at least that's no problem. But exposing
the structure of the error stack on the server may be a bit too much.
My current understanding, btw, is that the basic XML-RPC support for
Xend is going into the tree sometime this week (Ewan is looking at the
code now) and will be a part of the 3.0.2 release. This means that for
That's waht I was told too :-)
the 3.0.3 cycle, we'll be defining a standard API. This process
will be
starting soon (within the next couple of weeks hopefully).
Excellent ! Good good !
Hopefully we will be able to confront that with what is present in other
engines like l4 and QEmu and make sure at least for the 'common' APIs
the semantic is similar.
Daniel
--
Daniel Veillard | Red Hat http://redhat.com/
veillard(a)redhat.com | libxml GNOME XML XSLT toolkit http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/
4:35 p.m.
On Fri, 10 Mar 2006 17:21:52 -0500, Daniel Veillard wrote:
okay got it. Please add a Changelog entry when you commit to the
base :-)
Will do.
> int
> xend_pause(virConnectPtr xend, const char *name)
> {
> if (xend->xmlrpc)
> return xmlRpcCall(xend->xmlrpc, "xend.domain.pause",
"", "s", name)
> else
> return xend_op(xend, name, "op", "pause", NULL);
> }
Okay the steps needed look fairly clear, thanks :-)
One thing I should say is that I'm still contemplating changing the
XML-RPC interface in Xend to make the libvirt a little easier..
> Of course, using the xml-rpc code, we now have access to rich
fault
> information. Xend never actually returns errors for things and instead
> throws exceptions.
the new error code tries at least to extract the error message when
an HTTP POST or GEt fails with an error code, but the XML-RPC should
give a far more reliable framework for error handling.
If I recall correctly, the S-Expression/HTTP errors are always 501
Internal Server error with no extended error message. Of course, I may be
wrong.
> For the S-Expression/HTTP protocol, you just get a 501 and have
to
> return a meaningless error. With XML-RPC, those exceptions are
> actually serialized and sent over the wire. We may want to explore how
> we can make that information available to the user.
I would say as a buffer at least that's no problem. But exposing
the structure of the error stack on the server may be a bit too much.
What Ewan and I had discussed at the Summit, was standardizing a set of
exceptions for use as errors. I think this is a good idea. I would like
to always keep the stack trace in the exceptions though as it makes
debugging Xend considerably simpler.
For something like libvirt, we could just look at the faultCode and use
that to build an appropriate error message (based on current locale of
course). Perhaps we could also offer an extended error message too that
included the Xend faultMessage too.
> My current understanding, btw, is that the basic XML-RPC support
for
> Xend is going into the tree sometime this week (Ewan is looking at the
> code now) and will be a part of the 3.0.2 release. This means that for
That's waht I was told too :-)
> the 3.0.3 cycle, we'll be defining a standard API. This process will
> be starting soon (within the next couple of weeks hopefully).
Excellent ! Good good !
Hopefully we will be able to confront that with what is present in other
engines like l4 and QEmu and make sure at least for the 'common' APIs
the semantic is similar.
Oh, L4, good idea :-) I know just the person to talk to about that too...
Regards,
Anthony Liguori
Daniel
--
Daniel Veillard | Red Hat http://redhat.com/ veillard(a)redhat.com |
libxml GNOME XML XSLT toolkit http://xmlsoft.org/ http://veillard.com/
| Rpmfind RPM search engine http://rpmfind.net/
5:05 p.m.
On Fri, Mar 10, 2006 at 04:35:11PM -0600, Anthony Liguori wrote:
On Fri, 10 Mar 2006 17:21:52 -0500, Daniel Veillard wrote:
One thing I should say is that I'm still contemplating changing the
XML-RPC interface in Xend to make the libvirt a little easier..
Well don't think specifically in libvirt terms, but what canonical
interfaces are the most likely to be suitable for apps :-)
>> Of course, using the xml-rpc code, we now have access to
rich fault
>> information. Xend never actually returns errors for things and instead
>> throws exceptions.
>
> the new error code tries at least to extract the error message when
> an HTTP POST or GEt fails with an error code, but the XML-RPC should
> give a far more reliable framework for error handling.
If I recall correctly, the S-Expression/HTTP errors are always 501
Internal Server error with no extended error message. Of course, I may be
wrong.
There is an error message in the content of the GET/POST returned, I extract
it now, running "make tests" show:
/u/veillard/libvirt/python/tests
## running Python regression tests
libvir: Xen Daemon error : GET operation failed: No such domain test
That is a message output by the library. The python shutdown the 'test'
domain and loop trying to get state every second until a failure. The
failure ends up being reported (i.e. success :-)
"GET operation failed"
comes from libvirt, while
"No such domain test"
is the error message extrated from the failed HTTP request, I think it
work alike for POST ones.
Still this is limited and XML-RPC should be better in this respect :-)
>> For the S-Expression/HTTP protocol, you just get a 501 and
have to
>> return a meaningless error. With XML-RPC, those exceptions are
>> actually serialized and sent over the wire. We may want to explore how
>> we can make that information available to the user.
>
> I would say as a buffer at least that's no problem. But exposing
> the structure of the error stack on the server may be a bit too much.
What Ewan and I had discussed at the Summit, was standardizing a set of
exceptions for use as errors. I think this is a good idea. I would like
to always keep the stack trace in the exceptions though as it makes
debugging Xend considerably simpler.
Sure sounds a good idea
For something like libvirt, we could just look at the faultCode and
use
that to build an appropriate error message (based on current locale of
course). Perhaps we could also offer an extended error message too that
included the Xend faultMessage too.
appropriate error message yes. locale hum I'm not fond of it. libvirt
is too low in the stack, I would not expect the 'message' to be directly
useful to an user, but one must give as much informations as possible
to the software on top to be able to analyze and present a correct, in-context
error if needed.
> Excellent ! Good good !
> Hopefully we will be able to confront that with what is present in other
> engines like l4 and QEmu and make sure at least for the 'common' APIs
> the semantic is similar.
Oh, L4, good idea :-) I know just the person to talk to about that too...
Well Ronald Aigner who joined the list 2 days ago from Desden Univ certainly
seems to come from the l4 group there, but sure get more people on this list,
so we have less risk to fail our API designs ;-)
Daniel
--
Daniel Veillard | Red Hat http://redhat.com/
veillard(a)redhat.com | libxml GNOME XML XSLT toolkit http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/
4:57 p.m.
Of course, using the xml-rpc code, we now
have access to rich fault
information. Xend never actually returns errors for things and instead
throws exceptions.
the new error code tries at least to extract the error message when
an HTTP POST or GEt fails with an error code, but the XML-RPC should
give a far more reliable framework for error handling. ------------------------------------------------------------------------------------------------------------------|
|
|
| To: aliguori(a)us.ltcfwd.linux.ibm.com
|
| cc: libvir-list(a)redhat.com
|
| Subject: Re: [Libvir] XML-RPC support for libvirt
|
------------------------------------------------------------------------------------------------------------------|
On Fri, Mar 10, 2006 at 10:57:59AM -0600, Anthony Liguori wrote:
Howdy,
Evening ;-)
I'm about to checkin some XML-RPC code into CVS. The code
I'm checking
okay got it. Please add a Changelog entry when you commit to the base :-)
in won't compile by default (for now) as there's still a
little work to
do but I wanted to get something into the tree. Here are the tasks left:
1) Convert from dict to s-expressions to handle config returns. Right
now, the Xend XML-RPC code returns S-Expressions in the form of a
tuple. We just need a little code to convert from these tuples to
struct sexpr's.
2) Integrate my unit tests. I've got a number of unit tests that stress
the various bits of parsing code. I'd like to add a make check that
runs these unit tests and a make fullcheck that runs these unit tests
under valgrind.
3) Support XML-RPC over a domain socket. Right now I'm using nanohttp
which doesn't appear to allow different transports. There is some HTTP
PUT code already in the tree so I could use that if there isn't a more
clever solution.
4) Plumb the xend backend functions to XML-RPC. This is really straight
forward. It's just a matter of converting:
int
xend_pause(virConnectPtr xend, const char *name)
{
return xend_op(xend, name, "op", "pause", NULL);
}
To:
int
xend_pause(virConnectPtr xend, const char *name)
{
if (xend->xmlrpc)
return xmlRpcCall(xend->xmlrpc, "xend.domain.pause", "",
"s",
name)
else
return xend_op(xend, name, "op", "pause", NULL);
}
Okay the steps needed look fairly clear, thanks :-)
Of course, using the xml-rpc code, we now have access to rich fault
information. Xend never actually returns errors for things and instead
throws exceptions.
the new error code tries at least to extract the error message when
an HTTP POST or GEt fails with an error code, but the XML-RPC should
give a far more reliable framework for error handling.
For the S-Expression/HTTP protocol, you just get a
501 and have to return a meaningless error. With XML-RPC, those
exceptions are actually serialized and sent over the wire. We may want
to explore how we can make that information available to the user.
I would say as a buffer at least that's no problem. But exposing
the structure of the error stack on the server may be a bit too much.
My current understanding, btw, is that the basic XML-RPC support for
Xend is going into the tree sometime this week (Ewan is looking at the
code now) and will be a part of the 3.0.2 release. This means that for
That's waht I was told too :-)
the 3.0.3 cycle, we'll be defining a standard API. This process
will be
starting soon (within the next couple of weeks hopefully).
Excellent ! Good good !
Hopefully we will be able to confront that with what is present in other
engines like l4 and QEmu and make sure at least for the 'common' APIs
the semantic is similar.
Daniel
--
Daniel Veillard | Red Hat http://redhat.com/
veillard(a)redhat.com | libxml GNOME XML XSLT toolkit http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/
--
Libvir-list mailing list
Libvir-list(a)redhat.com
https://www.redhat.com/mailman/listinfo/libvir-list
5:18 p.m.
On Fri, Mar 10, 2006 at 02:57:57PM -0800, Gareth S Bestor wrote:
>> Of course, using the xml-rpc code, we now have access to
rich fault
>> information. Xend never actually returns errors for things and instead
>> throws exceptions.
>
> the new error code tries at least to extract the error message when
>an HTTP POST or GEt fails with an error code, but the XML-RPC should
>give a far more reliable framework for error handling.
Nice segway... I've been recently pinged a few times by our Xen CIM
consumers about the lack of good errors coming out of our providers (which
in turn are limited by what we get back from libxm today), especially in
regards to conditions that might cause a create() operation to fail. Do you
have a sense today of what errors we might expect to get reported back from
libvirt?
I think the prerequisite read is the following page where I tried to
write down how I planned and implemented error handling:
http://libvirt.org/errors.html
it's not coming from nowhere, it's actually the model used by libxml2
"structured" error handling the latest evolution of error processing in
that library. It's not completely broken as people seems to be satisfied
now with it (and its set of users is quite diverse :-)
Not that this will constitute any sort of meaningful
'requirements' with
which to write code, but the following is a list of errors that my Xen CIM
consumers handle today for the likes VMWare. I am trying to get more info
on under what specific circumstance(s) these are generated...
ERR_SUCCESS
ERR_UNABLE_TO_VERIFY_STATE
ERR_OUT_OF_DISK_SPACE
ERR_BAD_PARAMETER
ERR_VM_CONTROL_OP_FAILED
ERR_INVALID_PARM_NUM
ERR_CANNOT_ACCESS_DISK_FILE
ERR_UNKNOWN
ERR_VIRTUAL_DISK_CREATE_FAILED
ERR_VM_STUCK
ERR_CREDENTIALS_NOT_SET
ERR_UNACCEPTED_CREDENTIALS
ERR_OUT_OF_MEMORY
ERR_WRONG_STATE_FOR_OP
ERR_VM_NOT_FOUND
ERR_HOST_NOT_FOUND
ERR_ACCESS_DENIED
ERR_ALREADY_EXIST
ERR_OPERATION_FAILED
ERR_UNDOABLE_DISK_NOT_SUPPORTED
ERR_VMM_CMD_FORMAT_ERROR
ERR_COMMUNICATION_NOT_ESTABLISHED
ERR_FILE_COPY_FAILED
ERR_NAME_TOO_LONG
ERR_OS_NOT_SUPPORTED
ERR_MOUNT_FAILED_DIR_NOT_EMPTY
ERR_CANT_DISMOUNT_BOOT_OR_SYSTEM
ERR_FILE_IN_USE
That look actually a bit short to me for such a complete tool ;-)
I think error reporting is an area where we will definitely want to
drive
clients' requirements down into the likes of libvirt. Thnx.
Well you can consult libvirt current list of errors in
http://libvirt.org/html/libvirt-virterror.html#virErrorNumber
if we can get more details from the Xend internals then the
VIR_ERR_GET_FAILED and VIR_ERR_POST_FAILED could be replaced by
more precise informations. Also keep in mind that I would like
as much as possible to keep genericity in the API among the different
back-ends (and if know of a way to invite the WMWare folks to help here
I would be grateful :-).
Daniel
--
Daniel Veillard | Red Hat http://redhat.com/
veillard(a)redhat.com | libxml GNOME XML XSLT toolkit http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/
5:36 p.m.
T
Thanks Daniel. I agree on both counts: the list I attached (as given to
me) is still pretty anemic, and our Xen CIM consumer today would also
prefer generic, broadly useful common error codes and not just Xen (or
VMWare) specific ones, although some of this normalization will probably be
handled at the CIM level. I'll check out your suggested links. thnx again.
(and if know of a way to invite the WMWare folks to help here I would
be
grateful :-).
I will plant a seed and see if it grows... :-)
- G
Gareth S. Bestor, PhD.
IBM Linux Technology Center
M/S DES2-01
15300 SW Koll Parkway, Beaverton, OR 97006
503-578-3186, T/L 775-3186, Fax 503-578-3186
Daniel Veillard <veillard(a)redhat.com> on 03/10/2006 03:18:23 PM
Please respond to veillard(a)redhat.com
To: Gareth S Bestor/Poughkeepsie/IBM@IBMUS
cc: libvir-list(a)redhat.com
Subject: Re: [Libvir] XML-RPC support for libvirt
On Fri, Mar 10, 2006 at 02:57:57PM -0800, Gareth S Bestor wrote:
>> Of course, using the xml-rpc code, we now have access to
rich fault
>> information. Xend never actually returns errors for things and
instead
>> throws exceptions.
>
> the new error code tries at least to extract the error message when
>an HTTP POST or GEt fails with an error code, but the XML-RPC should
>give a far more reliable framework for error handling.
Nice segway... I've been recently pinged a few times by our Xen CIM
consumers about the lack of good errors coming out of our providers
(which
in turn are limited by what we get back from libxm today), especially
in
regards to conditions that might cause a create() operation to fail. Do
you
have a sense today of what errors we might expect to get reported
back
from
libvirt?
I think the prerequisite read is the following page where I tried to
write down how I planned and implemented error handling:
http://libvirt.org/errors.html
it's not coming from nowhere, it's actually the model used by libxml2
"structured" error handling the latest evolution of error processing in
that library. It's not completely broken as people seems to be satisfied
now with it (and its set of users is quite diverse :-)
Not that this will constitute any sort of meaningful
'requirements' with
which to write code, but the following is a list of errors that my Xen
CIM
consumers handle today for the likes VMWare. I am trying to get more
info
on under what specific circumstance(s) these are generated...
ERR_SUCCESS
ERR_UNABLE_TO_VERIFY_STATE
ERR_OUT_OF_DISK_SPACE
ERR_BAD_PARAMETER
ERR_VM_CONTROL_OP_FAILED
ERR_INVALID_PARM_NUM
ERR_CANNOT_ACCESS_DISK_FILE
ERR_UNKNOWN
ERR_VIRTUAL_DISK_CREATE_FAILED
ERR_VM_STUCK
ERR_CREDENTIALS_NOT_SET
ERR_UNACCEPTED_CREDENTIALS
ERR_OUT_OF_MEMORY
ERR_WRONG_STATE_FOR_OP
ERR_VM_NOT_FOUND
ERR_HOST_NOT_FOUND
ERR_ACCESS_DENIED
ERR_ALREADY_EXIST
ERR_OPERATION_FAILED
ERR_UNDOABLE_DISK_NOT_SUPPORTED
ERR_VMM_CMD_FORMAT_ERROR
ERR_COMMUNICATION_NOT_ESTABLISHED
ERR_FILE_COPY_FAILED
ERR_NAME_TOO_LONG
ERR_OS_NOT_SUPPORTED
ERR_MOUNT_FAILED_DIR_NOT_EMPTY
ERR_CANT_DISMOUNT_BOOT_OR_SYSTEM
ERR_FILE_IN_USE
That look actually a bit short to me for such a complete tool ;-)
I think error reporting is an area where we will definitely want to
drive
clients' requirements down into the likes of libvirt. Thnx.
Well you can consult libvirt current list of errors in
http://libvirt.org/html/libvirt-virterror.html#virErrorNumber
if we can get more details from the Xend internals then the
VIR_ERR_GET_FAILED and VIR_ERR_POST_FAILED could be replaced by
more precise informations. Also keep in mind that I would like
as much as possible to keep genericity in the API among the different
back-ends (and if know of a way to invite the WMWare folks to help here
I would be grateful :-).
Daniel
--
Daniel Veillard | Red Hat http://redhat.com/
veillard(a)redhat.com | libxml GNOME XML XSLT toolkit http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/
6834
days inactive
6834
days old
6 comments
4 participants
participants (4)
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Anthony Liguori -
Anthony Liguori -
Daniel Veillard -
Gareth S Bestor