Windows下Libvirt Java API使用教程(二)- 接口使用說明

 介紹完libvirt Java API的部署工作：

《Windows下Libvirt Java API使用教程(一)- 開發環境部署》

接下來我們就介紹一下接口的使用和代碼樣例。

libvirt的管理單位是單個主機，所以探測和監控接口所能獲取的信息的最大範圍也是主機。所以先從主機入手，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是用戶權限
            kvmConn = new Connect("qemu+tcp://10.4.54.10/system");
        } catch (LibvirtException e) {
            e.printStackTrace();
        }
    }

    /**
     * 主機信息探測接口驗證，驗證可以獲取的主機屬性和監控指標，分別考慮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
     * @author lihzh
     * @date 2012-5-15 下午1:37:37
     */
    private void doDetectHost(Connect conn) {
        try {
            // Returns the free memory for the connection
            // System.out.println("FreeMemory: " + conn.getFreeMemory());// 不支持

            // 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);
            // } 不支持

            // Provides the list of names of defined interfaces on this host

            // for (String interName : conn.listDefinedInterfaces()) {
            // System.out.println(interName);
            // } // 不支持

            // 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());
        } catch (LibvirtException e) {
            e.printStackTrace();
        }
    }

 分別在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>

      </domain>

    </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

number of core per socket: 8

memory size in kilobytes: 50276352

expected CPU frequency: 1995

string indicating the CPU model: x86_64

the number of NUMA cell, 1 for uniform: 1

number of CPU socket per node: 2

number of threads per core: 2

the total number of CPUs supported but not necessarily active in the host.: 32

Network name: default

Network filter name: allow-dhcp-server

Network filter name: qemu-announce-self-rarp

...

<capabilities>

 

  <host>

    <cpu>

      <arch>x86_64</arch>

      <features>

        <vmx/>

      </features>

    </cpu>

    <migration_features>

      <live/>

      <uri_transports>

        <uri_transport>xenmigr</uri_transport>

      </uri_transports>

    </migration_features>

  </host>

 

  <guest>

    <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'>

      </domain>

    </arch>

  </guest>

 

  ... 

</capabilities>

 

說明：

注1：標註不支持的，是在當前環境當前libvirt版本下，運行會報錯的接口。

  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，這麼多信息中，筆者關注的不多，有很多甚至說不出其代表的含義，筆者關注只是cpu的個數，核心數，內存總量等直觀信息。有就足以。
看完了主機，再看看虛擬機。一個虛擬化環境中的核心資源自然是虛擬機，所以其屬性和信息也自然多很多，上測試代碼：

/**
     * 測試探測虛擬機接口
     *
     * @author lihzh
     * @date 2012-5-16 上午11:14:20
     */
    @Test
    public void testDetectDomains() {
        // KVM
        doDetectDomains(kvmConn);
        // XEN
        doDetectDomains(xenConn);
    }

/**
     * 執行探測虛擬機測試函數
     *
     * @param conn
     * @author lihzh
     * @date 2012-5-16 上午11:15:27
     */
    private void doDetectDomains(Connect conn) {
        try {
            // Lists the active domains.(列出所有處於啓動(激活)狀態的虛擬機的id)
            for (int activeDomId : conn.listDomains()) {
                System.out.println("Active vm id: " + activeDomId);
                // 根據Id，探測各個虛擬機的詳細信息
                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()
                // 不支持
                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);
                }

            }

            // 列出所有停止態的虛擬機
            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>
    <disk type='file' device='disk'>
      <driver name='file'/>
      <source file='/opt/awcloud/instance/admin/i-546A099E/disk2'/>
      <target dev='hdb' bus='ide'/>
    </disk>
    <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'>
      <source path='/opt/awcloud/instance/admin/i-546A099E/console.log'/>
      <target port='0'/>
    </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
Domain network autostart: false
Inactive domain name: i-46A70811
Inactive domain name: i-38C20705
Inactive domain name: i-498E09B2
Inactive domain name: null
Inactive domain name: null
Inactive domain name: null
Inactive domain name: null
Inactive domain name: null

 

結果分析：
結果中基本包含了一個虛擬機組成的全部元素信息。如果你想做一個監控系統，你可以發現這裏有：

虛擬機的名字
虛擬機的Id
虛擬機的內存大小
虛擬CPU個數
虛擬機磁盤文件信息，磁盤文件的大小。甚至包括log等信息。
虛擬磁盤讀寫速率。
虛擬機網絡設備信息。Mac地址，設備類型等。
虛擬機網卡讀寫速率。

---

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：

Connect kvmConn = new Connect("qemu+tcp://10.4.54.10/system");

然後通過該連接獲取信息：

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返回中找到答案：

for (int activeDomId : conn.listDomains())

只是有的獲取的直接，有可能需要解析xml格式的返回值來獲取需要參數值。比如：disk的paht和interface的path。
最後再簡單介紹一下管控接口：

/**
     * 測試虛擬機的簡單操作
     *
     * @author lihzh
     * @date 2012-5-16 下午3:35:43
     */
    @Test
    public void testControlVM() {
        try {
            Domain domain = kvmConn.domainLookupByID(8);
            System.out.println("Domain state: " + domain.getInfo().state);
            domain.suspend();
            System.out.println("Domain state: " + domain.getInfo().state);
            for (int i = 0; i < 5; i++) {
                System.out.println("wait for: " + (5 - i));
                Thread.sleep(1000);
            }
            System.out.println("Resume vm.");
            domain.resume();
            System.out.println("Domain state: " + domain.getInfo().state);
        } catch (LibvirtException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

該用例主要測試了虛擬機的掛起和恢復操作。這類操作是比較簡單的（因爲無需參數）。一個複雜系統肯定需要包括虛擬機創建等操作。libvirt主要通過xml表述來創建資源，首先需要生成被創建虛擬機的完整描述，然後傳遞給創建的方法即可。描述的格式？呵呵，自然是上面測試結果給出的數據了。有興趣的，大家可以自己嘗試一下。libvirt的文檔，還不完善，不過對於創建這樣重要的功能，還是給出了說明。大家也可以下載官方的手冊作爲參考。
 

好了，相對於VMware、Xenserver等虛擬化平臺的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，信息量上，沒有其他的那麼充足。基於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。不過仍不失爲一個不錯的虛擬機環境操作的API，尤其是針對KVM/XEN的環境來說，可謂不二的選擇。