2. libvirt Python API的使用
6.1.1小节中已经介绍过，许多种编程语言都提供了libvirt的绑定。Python作为一种在Linux上比较流行的编程语言，它也提供了libvirt API的绑定。在使用Python调用libvirt之前，需要安装libvirt-python软件包，或者使用6.1.2节中介绍的方法来自行编译和安装libvirt及其Python API。
本次示例是基于RHEL 6.3系统自带libvirt和libvirt-python软件包来进行的，对libvirt-python以及Python中的libvirt API文件的查询，命令行如下：
[root@rhel6u3-ga ~]# rpm -q libvirt-python
libvirt-python-0.9.10-21.el6.x86_64
[root@rhel6u3-ga ~]# ls /usr/lib64/python2.6/site-packages/libvirt*
/usr/lib64/python2.6/site-packages/libvirtmod_qemu.so? /usr/lib64/python2.6/site-packages/libvirt.pyo
/usr/lib64/python2.6/site-packages/libvirtmod.so?????? /usr/lib64/python2.6/site-packages/libvirt_qemu.py
/usr/lib64/python2.6/site-packages/libvirt.py? ????????/usr/lib64/python2.6/site-packages/libvirt_qemu.pyc
/usr/lib64/python2.6/site-packages/libvirt.pyc???????? /usr/lib64/python2.6/site-packages/libvirt_qemu.pyo
如下是本次示例使用的一个Python小程序（libvirt-test.py），用于通过调用libvirt Python API来查询域的一些信息。该示例Python程序的源代码如下：
#!/usr/bin/python
# Get domain info via libvirt python API.
# Tested with python2.6 and libvirt-python-0.9.10 on a KVM host.
import libvirt
import sys
def createConnection():
conn = libvirt.openReadOnly(None)
if conn == None:
print ‘Failed to open connection to QEMU/KVM’
sys.exit(1)
else:
print ‘—–Connection is created successfully—–’
return conn
def closeConnnection(conn):
print ”
try:
conn.close()
except:
print ‘Failed to close the connection’
return 1
print ‘Connection is closed’
def getDomInfoByName(conn, name):
print ”
print ‘———– get domain info by name ———-”‘
try:
myDom = conn.lookupByName(name)
except:
print ‘Failed to find the domain with name “%s”‘ % name
return 1
print “Dom id: %d?? name: %s” % (myDom.ID(), myDom.name())
print “Dom state: %s” % myDom.state(0)
print “Dom info: %s” % myDom.info()
print “memory: %d MB” % (myDom.maxMemory()/1024)
print “memory status: %s” % myDom.memoryStats()
print “vCPUs: %d” % myDom.maxVcpus()
def getDomInfoByID(conn, id):
print ”
print ‘———– get domain info by ID ———-”‘
try:
myDom = conn.lookupByID(id)
except:
print ‘Failed to find the domain with ID “%d”‘ % id
return 1
print “Domain id is %d ; Name is %s” % (myDom.ID(), myDom.name())
if __name__ == ‘__main__’:
name1 = “kvm-guest”
name2 = “notExist”
id1 = 3
id2 = 9999
print “—Get domain info via libvirt python API—”
conn = createConnection()
getDomInfoByName(conn, name1)
getDomInfoByName(conn, name2)
getDomInfoByID(conn, id1)
getDomInfoByID(conn, id2)
closeConnnection(conn)
该示例程序比较简单，只是简单地调用libvirt Python API获取一些信息，这里唯一需要注意的是“import libvirt ”语句引入了libvirt.py这个API文件，然后才能够使用libvirt.openReadOnly 、conn.lookupByName 等libvirt中的方法。本次示例中，必须被引入的libvirt.py这个API文件的绝对路径在 /usr/lib64/python2.6/site-packages/libvirt.py ，它实际调用是/usr/lib64/python2.6/site-packages/ libvirtmod.so 这个共享库文件。
获得该示例Python程序后，运行该程序（libvirt-test.py），查看其运行结果，命令行操作如下：
[root@rhel6u3-ga kvm_demo]# python libvirt-test.py 2>/dev/null
—Get domain info via libvirt python API—
—–Connection is created successfully—–
———– get domain info by name ———-”
Dom id: 3?? name: kvm-guest
Dom state: [1, 1]
Dom info: [1, 1048576L, 1048576L, 4, 257070000000L]
memory: 1024 MB
memory status: {‘actual’: 1048576L, ‘rss’: 680228L}
vCPUs: 4
———– get domain info by name ———-”
Failed to find the domain with name “notExist”
———– get domain info by ID ———-”
Domain id is 3 ; Name is kvm-guest
———– get domain info by ID ———-”
Failed to find the domain with ID “9999″
Connection is closed
Original article: (KVM连载) 6.1.7 libvirt API 使用示例（Python API）
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