9:14 p.m.
Hello
I'm trying to find out how to detect if domain was destroyed and brought up between
two time moments, let's call it reads.
So far the best approach I could find is to compare domain ID from previous and current
read.
And this is my first question : is that reliable solution ? Or do you know any better ?
And related question is how to resolve virDomainPtr into domain ID ?
The only verified way of getting domain ID I know is to memorize it's UUID, then
call virConnectListDomains , then iterate over all returned domain IDs and resolve each
one's pointer using virDomainLookupByID , then get UUID by virDomainGetUUIDString
get domain ID of matching UUID's .
It seems too complex and I expect noticeable performance overhead, so looking for
something lighter.
I'm trying to get current domain ID using API function :
char * virDomainGetMetadata (virDomainPtr domain, int type, const char * uri,
unsigned int flags)
I'm not sure it's relevant function, since domain ID is contained not in
metadata subsection but in opening <domain> markup.
In fact I wasn't even able to get any data using that function call since I don't
know how to construct valid URI. Do you know any doc or examples explaining that ?
Any help appreciated
Krzysztof
--------------------------------------------------------------
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Registered in Ireland
Registered Office: Collinstown Industrial Park, Leixlip, County Kildare
Registered Number: 308263
This e-mail and any attachments may contain confidential material for the sole
use of the intended recipient(s). Any review or distribution by others is
strictly prohibited. If you are not the intended recipient, please contact the
sender and delete all copies.
9:38 p.m.
On 06.03.2017 14:14, Matczak, KrzysztofX wrote:
Hello
I'm trying to find out how to detect if domain was destroyed and brought up between
two time moments, let's call it reads.
So far the best approach I could find is to compare domain ID from previous and current
read.
And this is my first question : is that reliable solution ? Or do you know any better ?
Listen to the events. If domain is destroyed/started libvirt fires up an
event. The domain ID is not necessarily unique. For instance:
a) start a domain and assume it's the first one started. It will have ID=1.
b) destroy it.
c) restart libvirtd.
d) start the domain again - it will have ID=1.
This applies to qemu driver, other drivers might have different meaning
for domain IDs - e.g. LXC driver reports PID of the container's init in
which case you can make no assumptions about it.
And related question is how to resolve virDomainPtr into domain ID ?
virDomainGetID().
The only verified way of getting domain ID I know is to memorize
it's UUID, then call virConnectListDomains , then iterate over all returned domain
IDs and resolve each one's pointer using virDomainLookupByID , then get UUID by
virDomainGetUUIDString get domain ID of matching UUID's .
It seems too complex and I expect noticeable performance overhead, so looking for
something lighter.
I'm trying to get current domain ID using API function :
char * virDomainGetMetadata (virDomainPtr domain, int type, const char * uri,
unsigned int flags)
I'm not sure it's relevant function, since domain ID is contained not in
metadata subsection but in opening <domain> markup.
In fact I wasn't even able to get any data using that function call since I
don't know how to construct valid URI. Do you know any doc or examples explaining that
?
Documentation might come handy:
http://libvirt.org/html/libvirt-libvirt-domain.html#virDomainSetMetadata
http://libvirt.org/html/libvirt-libvirt-domain.html#virDomainGetMetadata
or just look into our test suite:
http://libvirt.org/git/?p=libvirt.git;a=blob;f=tests/metadatatest.c;h=55d...
Michal
9:51 p.m.
Listen to the events
I guess that would require running my own
polling thread, right ? I wanted to avoid that ...
Thanks for help
On 06.03.2017 14:14, Matczak, KrzysztofX wrote:
Hello
I'm trying to find out how to detect if domain was destroyed and brought up between
two time moments, let's call it reads.
So far the best approach I could find is to compare domain ID from previous and current
read.
And this is my first question : is that reliable solution ? Or do you know any better ?
Listen to the events. If domain is destroyed/started libvirt fires up an event. The domain
ID is not necessarily unique. For instance:
a) start a domain and assume it's the first one started. It will have ID=1.
b) destroy it.
c) restart libvirtd.
d) start the domain again - it will have ID=1.
This applies to qemu driver, other drivers might have different meaning for domain IDs -
e.g. LXC driver reports PID of the container's init in which case you can make no
assumptions about it.
And related question is how to resolve virDomainPtr into domain ID ?
virDomainGetID().
The only verified way of getting domain ID I know is to memorize
it's UUID, then call virConnectListDomains , then iterate over all returned domain
IDs and resolve each one's pointer using virDomainLookupByID , then get UUID by
virDomainGetUUIDString get domain ID of matching UUID's .
It seems too complex and I expect noticeable performance overhead, so looking for
something lighter.
I'm trying to get current domain ID using API function :
char * virDomainGetMetadata (virDomainPtr domain, int type, const char * uri,
unsigned int flags)
I'm not sure it's relevant function, since domain ID is contained not in
metadata subsection but in opening <domain> markup.
In fact I wasn't even able to get any data using that function call since I
don't know how to construct valid URI. Do you know any doc or examples explaining that
?
Documentation might come handy:
http://libvirt.org/html/libvirt-libvirt-domain.html#virDomainSetMetadata
http://libvirt.org/html/libvirt-libvirt-domain.html#virDomainGetMetadata
or just look into our test suite:
http://libvirt.org/git/?p=libvirt.git;a=blob;f=tests/metadatatest.c;h=55d...
Michal
--------------------------------------------------------------
Intel Research and Development Ireland Limited
Registered in Ireland
Registered Office: Collinstown Industrial Park, Leixlip, County Kildare
Registered Number: 308263
This e-mail and any attachments may contain confidential material for the sole
use of the intended recipient(s). Any review or distribution by others is
strictly prohibited. If you are not the intended recipient, please contact the
sender and delete all copies.
4:21 a.m.
One additional question regarding event listening:
How to control timeout on call to virEventRunDefaultImpl in event loop ? Default
timeout when there are no events is something like 5s , which is way too much for my
application. I can't find related examples and API docs are not quite straightforward
in that matter
thanks
Krzysztof
Listen to the events
I guess that would require running my own
polling thread, right ? I wanted to avoid that ...
Thanks for help
On 06.03.2017 14:14, Matczak, KrzysztofX wrote:
Hello
I'm trying to find out how to detect if domain was destroyed and brought up between
two time moments, let's call it reads.
So far the best approach I could find is to compare domain ID from previous and current
read.
And this is my first question : is that reliable solution ? Or do you know any better ?
Listen to the events. If domain is destroyed/started libvirt fires up an event. The domain
ID is not necessarily unique. For instance:
a) start a domain and assume it's the first one started. It will have ID=1.
b) destroy it.
c) restart libvirtd.
d) start the domain again - it will have ID=1.
This applies to qemu driver, other drivers might have different meaning for domain IDs -
e.g. LXC driver reports PID of the container's init in which case you can make no
assumptions about it.
And related question is how to resolve virDomainPtr into domain ID ?
virDomainGetID().
The only verified way of getting domain ID I know is to memorize
it's UUID, then call virConnectListDomains , then iterate over all returned domain
IDs and resolve each one's pointer using virDomainLookupByID , then get UUID by
virDomainGetUUIDString get domain ID of matching UUID's .
It seems too complex and I expect noticeable performance overhead, so looking for
something lighter.
I'm trying to get current domain ID using API function :
char * virDomainGetMetadata (virDomainPtr domain, int type, const char * uri,
unsigned int flags)
I'm not sure it's relevant function, since domain ID is contained not in
metadata subsection but in opening <domain> markup.
In fact I wasn't even able to get any data using that function call since I
don't know how to construct valid URI. Do you know any doc or examples explaining that
?
Documentation might come handy:
http://libvirt.org/html/libvirt-libvirt-domain.html#virDomainSetMetadata
http://libvirt.org/html/libvirt-libvirt-domain.html#virDomainGetMetadata
or just look into our test suite:
http://libvirt.org/git/?p=libvirt.git;a=blob;f=tests/metadatatest.c;h=55d...
Michal
--------------------------------------------------------------
Intel Research and Development Ireland Limited Registered in Ireland Registered Office:
Collinstown Industrial Park, Leixlip, County Kildare Registered Number: 308263
This e-mail and any attachments may contain confidential material for the sole use of the
intended recipient(s). Any review or distribution by others is strictly prohibited. If you
are not the intended recipient, please contact the sender and delete all copies.
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--------------------------------------------------------------
Intel Research and Development Ireland Limited
Registered in Ireland
Registered Office: Collinstown Industrial Park, Leixlip, County Kildare
Registered Number: 308263
This e-mail and any attachments may contain confidential material for the sole
use of the intended recipient(s). Any review or distribution by others is
strictly prohibited. If you are not the intended recipient, please contact the
sender and delete all copies.
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3 comments
2 participants
participants (2)
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Matczak, KrzysztofX -
Michal Privoznik