介紹完libvirt Java API的部署工作：
接下來我們就介紹一下接口的使用和代碼樣例。
libvirt的管理機關是單個主機，是以探測和監控接口所能擷取的資訊的最大範圍也是主機。是以先從主機入手，驗證libvirt接口。主機（libvirt所在管理節點）探測相關接口驗證代碼如下：
@Before
public void init() {
System.setProperty("jna.library.path",
"D:/Git-Repo/git/libvirt-java/libvirt-java/src/test/java/kubi/coder/");
try {
xenConn = new Connect("xen+tcp://10.4.55.203/");
// system代表擁有系統權限/session是使用者權限
kvmConn = new Connect("qemu+tcp://10.4.54.10/system");
} catch (LibvirtException e) {
e.printStackTrace();
}
}
/**
* 主機資訊探測接口驗證，驗證可以擷取的主機屬性和監控名額，分别考慮Xen環境和KVM環境
*
* @author lihzh
* @date 2012-5-15 下午1:28:00
*/
@Test
public void testDetectHost() {
// KVM
doDetectHost(kvmConn);
// XEN
doDetectHost(xenConn);
* 執行探測主機測試函數
* @param conn
* @date 2012-5-15 下午1:37:37
private void doDetectHost(Connect conn) {
// Returns the free memory for the connection
// System.out.println("FreeMemory: " + conn.getFreeMemory());// 不支援
// Returns the system hostname on which the hypervisor is running.
// (the result of the gethostname(2) system call)
// If we are connected to a remote system,
// then this returns the hostname of the remote system
System.out.println("Host name: " + conn.getHostName());
// Gets the name of the Hypervisor software used.
System.out.println("Type: " + conn.getType());
// Gets the version level of the Hypervisor running. This may work
// only with hypervisor call, i.e. with priviledged access to the
// hypervisor, not with a Read-Only connection. If the version can't
// be extracted by lack of capacities returns 0.
// Returns:
// major * 1,000,000 + minor * 1,000 + release
System.out.println(conn.getVersion());
NodeInfo nodeInfo = conn.nodeInfo();
System.out.println("the number of active CPUs: " + nodeInfo.cpus);
System.out.println("number of core per socket: " + nodeInfo.cores);
System.out.println("memory size in kilobytes: " + nodeInfo.memory);
System.out.println("expected CPU frequency: " + nodeInfo.mhz);
System.out.println("string indicating the CPU model: "
+ nodeInfo.model);
System.out.println("the number of NUMA cell, 1 for uniform: "
+ nodeInfo.nodes);
System.out.println("number of CPU socket per node: "
+ nodeInfo.sockets);
System.out.println("number of threads per core: "
+ nodeInfo.threads);
System.out
.println("the total number of CPUs supported but not necessarily active in the host.: "
+ nodeInfo.maxCpus());
// for (String interName : conn.listInterfaces()) {
// System.out.println(interName);
// } 不支援
// Provides the list of names of defined interfaces on this host
// for (String interName : conn.listDefinedInterfaces()) {
// } // 不支援
// Lists the active networks.
for (String networkName : conn.listNetworks()) {
System.out.println("Network name: " + networkName);
}
// Lists the names of the network filters
for (String networkFilterName : conn.listNetworkFilters()) {
System.out.println("Network filter name: " + networkFilterName);
System.out.println(conn.getCapabilities());
分别在KVM和XEN環境下測試了libvirt接口，測試結果如下：
Host name: s5410
Type: QEMU
9001
the number of active CPUs: 64
number of core per socket: 8
memory size in kilobytes: 49444896
expected CPU frequency: 2131
string indicating the CPU model: x86_64
the number of NUMA cell, 1 for uniform: 1
number of CPU socket per node: 4
number of threads per core: 2
the total number of CPUs supported but not necessarily active in the host.: 64
Network name: hello
Network name: default
Network filter name: no-other-l2-traffic
Network filter name: allow-dhcp
...
<capabilities>
<host>
<uuid>30b940dd-f79a-21a2-82d5-ddc1b1b4a7e4</uuid>
<cpu>
<arch>x86_64</arch>
<model>core2duo</model>
<topology sockets='4' cores='8' threads='2'/>
<feature name='lahf_lm'/>
<feature name='rdtscp'/>
...
</cpu>
<migration_features>
<live/>
<uri_transports>
<uri_transport>tcp</uri_transport>
</uri_transports>
</migration_features>
</host>
<guest>
<os_type>hvm</os_type>
<arch name='i686'>
<wordsize>32</wordsize>
<emulator>/usr/libexec/qemu-kvm</emulator>
<machine>rhel5.4.0</machine>
<machine canonical='rhel5.4.0'>pc</machine>
<machine>rhel5.4.4</machine>
<machine>rhel5.5.0</machine>
<machine>rhel5.6.0</machine>
<domain type='qemu'>
</domain>
<domain type='kvm'>
<emulator>/usr/libexec/qemu-kvm</emulator>
</arch>
<features>
<cpuselection/>
<pae/>
<nonpae/>
<acpi default='on' toggle='yes'/>
<apic default='on' toggle='no'/>
</features>
</guest>
...
</capabilities>
Host name: s55203
Type: Xen
3001000
the number of active CPUs: 32
memory size in kilobytes: 50276352
expected CPU frequency: 1995
number of CPU socket per node: 2
the total number of CPUs supported but not necessarily active in the host.: 32
Network filter name: allow-dhcp-server
Network filter name: qemu-announce-self-rarp
<features>
<vmx/>
</features>
<uri_transport>xenmigr</uri_transport>
<os_type>xen</os_type>
<arch name='x86_64'>
<wordsize>64</wordsize>
<emulator>/usr/lib64/xen/bin/qemu-dm</emulator>
<machine>xenpv</machine>
<domain type='xen'>
...
說明：
注1：标注不支援的，是在目前環境目前libvirt版本下，運作會報錯的接口。
unsupported in sys interface
注2：名詞解釋
hvm:
gives similar information but when running a 32 bit OS fully virtualized with Xen using the hvm support。
numa：
For processors that support hyperthreading, this is the number of hyperthreads
they have per core. On a machine that doesn't support hyperthreading, this
will be 1.
說實話，這麼多資訊中，筆者關注的不多，有很多甚至說不出其代表的含義，筆者關注隻是cpu的個數，核心數，記憶體總量等直覺資訊。有就足以。
看完了主機，再看看虛拟機。一個虛拟化環境中的核心資源自然是虛拟機，是以其屬性和資訊也自然多很多，上測試代碼：
/**
* 測試探測虛拟機接口
*
* @author lihzh
* @date 2012-5-16 上午11:14:20
public void testDetectDomains() {
// KVM
doDetectDomains(kvmConn);
// XEN
doDetectDomains(xenConn);
}
* 執行探測虛拟機測試函數
* @param conn
* @date 2012-5-16 上午11:15:27
private void doDetectDomains(Connect conn) {
try {
// Lists the active domains.(列出所有處于啟動(激活)狀态的虛拟機的id)
for (int activeDomId : conn.listDomains()) {
System.out.println("Active vm id: " + activeDomId);
// 根據Id，探測各個虛拟機的詳細資訊
Domain domain = conn.domainLookupByID(activeDomId);
// Gets the hypervisor ID number for the domain
System.out.println("Domain id: " + domain.getID());
// Gets the public name for this domain
System.out.println("Domain name: " + domain.getName());
// Gets the type of domain operation system.
System.out.println("Domain os type: " + domain.getOSType());
// Gets the UUID for this domain as string.
System.out.println("Domain uuid: " + domain.getUUIDString());
// Retrieve the maximum amount of physical memory allocated to a
// domain.
System.out.println("Domain max memory: "
+ domain.getMaxMemory());
// Provides the maximum number of virtual CPUs supported for the
// guest VM. If the guest is inactive, this is basically the
// same as virConnectGetMaxVcpus. If the guest is running this
// will reflect the maximum number of virtual CPUs the guest was
// booted with.
System.out.println("Domain max vcpu: " + domain.getMaxVcpus());
// Provides an XML description of the domain. The description
// may be
// reused later to relaunch the domain with createLinux().
System.out.println("Domain xml description: "
+ domain.getXMLDesc(0));
System.out.println("Domain maxMen allowed: "
+ domain.getInfo().maxMem);
System.out.println("Domain memory: " + domain.getInfo().memory);
// domain.getJobInfo()
// 不支援
System.out.println("Domain state: " + domain.getInfo().state);
// Provides a boolean value indicating whether the network is
// configured to be automatically started when the host machine
// boots.
System.out.println("Domain network autostart: "
+ domain.getAutostart());
// Extracts information about virtual CPUs of this domain
for (VcpuInfo vcpuInfo : domain.getVcpusInfo()) {
System.out.println("cpu: " + vcpuInfo.cpu);
System.out.println("cpu time: " + vcpuInfo.cpuTime);
System.out.println("cpu number: " + vcpuInfo.number);
System.out.println("cpu state: " + vcpuInfo.state);
}
// 如果是KVM環境
if (conn.getURI().startsWith("qemu")) {
// This function returns block device (disk) stats for block
// devices attached to the domain
DomainBlockInfo blockInfo = domain
.blockInfo("/opt/awcloud/instance/admin/"
+ domain.getName() + "/disk");
System.out.println("Disk Capacity: "
+ blockInfo.getCapacity());
System.out.println("Disk allocation: "
+ blockInfo.getAllocation());
System.out.println("Disk physical: "
+ blockInfo.getPhysical());
DomainBlockStats blockStats = domain.blockStats("vda");
// 磁盤讀取請求總數
System.out.println("read request num: " + blockStats.rd_req);
// 磁盤讀取總bytes數
System.out.println("read request num: " + blockStats.rd_bytes);
// 磁盤寫入請求總數
System.out.println("read request num: " + blockStats.wr_req);
// 磁盤寫入總bytes數
System.out.println("read request num: " + blockStats.wr_bytes);
}
// 列出所有停止态的虛拟機
for (String name : conn.listDefinedDomains()) {
System.out.println("Inactive domain name: " + name);
} catch (LibvirtException e) {
e.printStackTrace();
}
循環較多，摘取部分結果如下：
Active vm id: 53
Domain id: 53
Domain name: i-546A099E
Domain os type: hvm
Domain uuid: e608560a-2c03-8e48-2e60-d0d01693f530
Domain max memory: 147456
Domain max vcpu: 1
Domain xml description: <domain type='xen' id='53'>
<name>i-546A099E</name>
<uuid>e608560a-2c03-8e48-2e60-d0d01693f530</uuid>
<memory>131072</memory>
<currentMemory>131072</currentMemory>
<vcpu>1</vcpu>
<os>
<type>hvm</type>
<loader>/usr/lib/xen/boot/hvmloader</loader>
<boot dev='hd'/>
</os>
<features>
<acpi/>
<apic/>
<pae/>
</features>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>restart</on_crash>
<devices>
<emulator>/usr/lib64/xen/bin/qemu-dm</emulator>
<disk type='file' device='disk'>
<driver name='file'/>
<source file='/opt/awcloud/instance/admin/i-546A099E/disk'/>
<target dev='hda' bus='ide'/>
</disk>
<source file='/opt/awcloud/instance/admin/i-546A099E/disk2'/>
<target dev='hdb' bus='ide'/>
<interface type='bridge'>
<mac address='d0:0d:54:6a:09:9e'/>
<source bridge='xenbr0'/>
<script path='vif-bridge'/>
<target dev='vif53.0'/>
</interface>
<serial type='file'>
<source path='/opt/awcloud/instance/admin/i-546A099E/console.log'/>
<target port='0'/>
</serial>
<console type='file'>
</console>
<input type='tablet' bus='usb'/>
<input type='mouse' bus='ps2'/>
<graphics type='vnc' port='17237' autoport='no'/>
</devices>
</domain>
Domain maxMen allowed: 147456
Domain memory: 139140
Domain state: VIR_DOMAIN_BLOCKED
Domain network autostart: false
cpu: 31
cpu time: 2225977676675
cpu number: 0
cpu state: VIR_VCPU_BLOCKED
Inactive domain name: i-46A70811
Inactive domain name: i-38C20705
Inactive domain name: i-498E09B2
Inactive domain name: null
結果分析：
結果中基本包含了一個虛拟機組成的全部元素資訊。如果你想做一個監控系統，你可以發現這裡有：
虛拟機的名字
虛拟機的Id
虛拟機的記憶體大小
虛拟CPU個數
虛拟機磁盤檔案資訊，磁盤檔案的大小。甚至包括log等資訊。
虛拟磁盤讀寫速率。
虛拟機網絡裝置資訊。Mac位址，裝置類型等。
虛拟機網卡讀寫速率。
基本可以滿足一個監控系統的需求。
說明一下上面的測試代碼。libvirt Java API的入口基本都是通過Connect這個類，也就是首先建立與被管理主機之間的連接配接：
Connect kvmConn = new Connect("qemu+tcp://10.4.54.10/system");
然後通過該連接配接擷取資訊：
conn.listDomains()
一個接口的如果需要接受參數：
conn.domainLookupByID(activeDomId)
肯定可以從其他的接口傳回中找到答案：
for (int activeDomId : conn.listDomains())
隻是有的擷取的直接，有可能需要解析xml格式的傳回值來擷取需要參數值。比如：disk的paht和interface的path。
最後再簡單介紹一下管控接口：
* 測試虛拟機的簡單操作
* @date 2012-5-16 下午3:35:43
public void testControlVM() {
Domain domain = kvmConn.domainLookupByID(8);
System.out.println("Domain state: " + domain.getInfo().state);
domain.suspend();
for (int i = 0; i < 5; i++) {
System.out.println("wait for: " + (5 - i));
Thread.sleep(1000);
System.out.println("Resume vm.");
domain.resume();
} catch (InterruptedException e) {
該用例主要測試了虛拟機的挂起和恢複操作。這類操作是比較簡單的（因為無需參數）。一個複雜系統肯定需要包括虛拟機建立等操作。libvirt主要通過xml表述來建立資源，首先需要生成被建立虛拟機的完整描述，然後傳遞給建立的方法即可。描述的格式？呵呵，自然是上面測試結果給出的資料了。有興趣的，大家可以自己嘗試一下。libvirt的文檔，還不完善，不過對于建立這樣重要的功能，還是給出了說明。大家也可以下載下傳官方的手冊作為參考。
好了，相對于VMware、Xenserver等虛拟化平台的SDK，libvirt的Java API還是比較簡單的，上手很快，結構很簡單。當然，功能上可能還是有所欠缺，資訊量上，沒有其他的那麼充足。基于XML的方式操作資源，減少了接口的個數，使調用更直接，但是對開發人員卻增加了困難。不過仍不失為一個不錯的虛拟機環境操作的API，尤其是針對KVM/XEN的環境來說，可謂不二的選擇。
本文轉自mushiqianmeng 51CTO部落格，原文連結：http://blog.51cto.com/mushiqianmeng/865174，如需轉載請自行聯系原作者
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