libvirt-java怎么获得虚拟机内存使用率
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发布时间：2022-05-15 05:22
共1个回答
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时间：2023-10-09 23:13
幸好livirt提供了API，所以我打算尝试用API写一个Nagios的插件来满足的我的需求，我的想法就是分别2次获得虚拟机的CPU时间，并分别记录2次取得数据时的系统时间，然后根据差值来计算，在理论上是存在一些误差的。
1.要使用API，首先需要安装libvirt-devel
[root@aikaiyuan ~]# yum -y install libvirt-devel
2.我的代码如下，文件名为vCpu.c
/**
* Program Name: vCpu.c
* Author: steptodream
* Description:A simple plugin to get vps cpu usage
* for nagios(nrpe) by libvirt api
* Compile:gcc -o vCpu vCpu.c -lvirt
*/
#include <stdlib.h>
#include <stdio.h>
#include <libvirt/libvirt.h>
/* define the exit status for nagios */
#define OK 0
#define WARNING 1
#define CRITICAL 2
#define UNKNOWN 3
/* get cpu time of the given name */
double getCpuTime(char *vpsName,virConnectPtr conn) {
virDomainInfo info;
virDomainPtr domain = NULL;
int ret;
/* Find the domain of the given name */
domain = virDomainLookupByName(conn, vpsName);
if (domain == NULL) {
printf("Failed to find the vps called %sn", vpsName);
exit(OK);
}
/* Get the information of the domain */
ret = virDomainGetInfo(domain, &info);
virDomainFree(domain);
if (ret < 0) {
printf("Failed to get information for %sn", vpsName);
exit(OK);
}
return info.cpuTime;
}
int main(int argc,char * argv[])
{
char *vpsName; /* vps name */
int interval = 1; /* check interval */
double warning; /* warning value */
double critical; /* critical value */
double cpuUsage; /* cpu usage of the vps */
struct timeval startTime; /* time of the first time to get cpu time */
struct timeval endTime; /* time of the second time to get cpu time */
int realTime; /* real interval between two times */
long long startCpuTime; /* cpu time of the first time */
long long endCpuTime; /* cpu time of the second time */
int cpuTime; /* value of startCpuTime - endCpuTime */
char *output; /* output data for nagios */
int ret; /* exit status for nagios */
virConnectPtr conn; /* connection pointer */
switch (argc){
case 5:
interval = atoi(argv[4]);
case 4:
vpsName = argv[1];
warning = atof(argv[2]);
critical = atof(argv[3]);
break;
default:
printf("Usage:vCpu <vName> <warning> <critical> [interval]nn");
return OK;
}
/* connect to local Xen Host */
conn = virConnectOpenReadOnly(NULL);
if (conn == NULL) {
printf("Failed to connect to local Xen Hostn");
return OK;
}
/* get cpu time the first time */
startCpuTime = getCpuTime(vpsName, conn);
/* get start time */
if (gettimeofday(&startTime, NULL) == -1) {
printf("Failed to get start timen");
return OK;
}
/* wait for some seconds */
sleep(interval);
/* get cpu time the second time */
endCpuTime = getCpuTime(vpsName, conn);
/* get end time */
if (gettimeofday(&endTime, NULL) == -1) {
printf("Failed to get end timen");
return OK;
}
/* colose connection */
virConnectClose(conn);
/* calculate the usage of cpu */
cpuTime = (startCpuTime - endCpuTime) / 1000;
realTime = 1000000 * (startTime.tv_sec - endTime.tv_sec) +
(startTime.tv_usec - endTime.tv_usec);
cpuUsage = cpuTime / (double)(realTime);
/* display cpuUsage by percentage */
cpuUsage *= 100;
/* make output data and exit status for nagios*/
if (cpuUsage > critical) {
output = "CRITICAL";
ret = CRITICAL;
} else if (cpuUsage > warning){
output = "WARNING";
ret = WARNING;
} else {
output = "OK";
ret = OK;
}
printf("%s CPU:%.2f%|CPU=%.2f",output,cpuUsage,cpuUsage);
return ret;
}
3.编译测试，根据我的需求，我设置了3个必须参数和1个可选参数，分别是虚拟机名称vpsName,警告值warning(百分比值),危急值critical(百分比值)和检查间隔interval(秒)
[root@aikaiyuan ~]# gcc -o vCpu vCpu.c -lvirt
[root@aikaiyuan ~]# ./vCpu vmtest 1 2
OK CPU:0.20%|CPU=0.20
当然了，你同时可以再打开一个终端，用xm top vmtest来获取vmtest的cpu使用率，然后对比一下取值是否接近一致。我们再来看看返回值是否正常，因为Nagios是靠这个来判断服务状态的。
[root@aikaiyuan ~]# echo $?
0
注意，我的具体要求是检测指定名称的虚拟机的CPU使用率，如果超过了规定的warning或者critical值，就给使用者发邮件，所以在没有得到数据或者程序出错的情况，我都是以正常状态退出程序的。
另外，本人开发经验薄弱，所以代码里难免存在错误和不合理的地方以及不完善的地方（比如参数的合法性检验），仅供参考。
最后，关于代码中时间，我是以微秒(us)为统一单位来计算的，得到的cpu的时间是纳秒(ns)，这个在结构体virDomainInfo定义中可以看到：
struct virDomainInfo{
unsigned char state : the running state, one of virDomainState
unsigned long maxMem : the maximum memory in KBytes allowed
unsigned long memory : the memory in KBytes used by the domain
unsigned short nrVirtCpu : the number of virtual CPUs for the domain
unsigned long long cpuTime : the CPU time used in nanoseconds
}
而通过gettimeofday取得存取到timeval结构体里的时间，包含tv_sec(s秒)和tv_usec（us微秒）这2种单位，可以从timeval结构体的定义中看到：
struct timeval {
time_t tv_sec; /* seconds */
suseconds_t tv_usec; /* microseconds */
};
