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d2978caea7
Signed-off-by: Pavel Hrdina <phrdina@redhat.com> Signed-off-by: Peter Krempa <pkrempa@redhat.com> Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
80 lines
2.5 KiB
ReStructuredText
80 lines
2.5 KiB
ReStructuredText
===================
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Python API bindings
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===================
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The Python binding should be complete and are mostly automatically generated
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from the formal description of the API in xml. The bindings are articulated
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around 2 classes ``virConnect`` and virDomain mapping to the C types. Functions
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in the C API taking either type as argument then becomes methods for the
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classes, their name is just stripped from the virConnect or virDomain(Get)
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prefix and the first letter gets converted to lower case, for example the C
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functions:
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``int virConnectNumOfDomains (virConnectPtr conn);``
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``int virDomainSetMaxMemory (virDomainPtr domain, unsigned long memory);``
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become
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``virConnect::numOfDomains(self)``
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``virDomain::setMaxMemory(self, memory)``
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This process is fully automated, you can get a summary of the conversion in the
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file libvirtclass.txt present in the python dir or in the docs.There is a couple
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of function who don't map directly to their C counterparts due to specificities
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in their argument conversions:
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- ``virConnectListDomains`` is replaced by ``virDomain::listDomainsID(self)``
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which returns a list of the integer ID for the currently running domains
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- ``virDomainGetInfo`` is replaced by ``virDomain::info()`` which returns a
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list of
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#. state: one of the state values (virDomainState)
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#. maxMemory: the maximum memory used by the domain
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#. memory: the current amount of memory used by the domain
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#. nbVirtCPU: the number of virtual CPU
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#. cpuTime: the time used by the domain in nanoseconds
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So let's look at a simple example:
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::
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import libvirt
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import sys
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try:
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conn = libvirt.openReadOnly(None)
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except libvirt.libvirtError:
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print('Failed to open connection to the hypervisor')
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sys.exit(1)
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try:
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dom0 = conn.lookupByName("Domain-0")
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except libvirt.libvirtError:
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print('Failed to find the main domain')
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sys.exit(1)
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print("Domain 0: id %d running %s" % (dom0.ID(), dom0.OSType()))
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print(dom0.info())
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There is not much to comment about it, it really is a straight mapping from the
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C API, the only points to notice are:
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- the import of the module called ``libvirt``
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- getting a connection to the hypervisor, in that case using the openReadOnly
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function allows the code to execute as a normal user.
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- getting an object representing the Domain 0 using lookupByName
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- if the domain is not found a libvirtError exception will be raised
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- extracting and printing some information about the domain using various
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methods associated to the virDomain class.
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