Java obtains system information of linux services (cpu usage, memory usage, system load)

1 code

1.1 Tools

Description:

• For cpu usage rate, you can use the jdk tool method, but some blogs say that it is not accurate, and it is not used here. It is achieved through /proc/stat.
• The memory usage rate is realized by the method of jdk tools.
• The system load is realized through calculation using the uptime command.

import com.sun.management.OperatingSystemMXBean;
import lombok.extern.slf4j.Slf4j;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.lang.management.ManagementFactory;
import java.math.BigDecimal;
import java.util.StringTokenizer;

@Slf4j
public class LinuxInfoUtil {
    private static final String CPU_FILE = "/proc/stat";
    private static final String LOAD_COMMAND = "uptime";

    /**
     * 获得Linux cpu使用率 pcpu =100* (total-idle)/total
     * total = total2-total1
     * idle = idle2 -idle1
     * total1 = user1+nice1+system1+idle1+iowait1+irq1+softirq1+stealstolen1+guest1+guest_nice1
     */
    public static BigDecimal getCpuInfo() {
        try {
            File file = new File(CPU_FILE);
            BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(file)));
            StringTokenizer procStatFirstLine = new StringTokenizer(br.readLine());
            CpuInfoBean cpuInfoBean1 = new CpuInfoBean(procStatFirstLine);
            BigDecimal total1 = cpuInfoBean1.getCpuTotal();
            Thread.sleep(1000);
            br = new BufferedReader(new InputStreamReader(new FileInputStream(file)));
            procStatFirstLine = new StringTokenizer(br.readLine());
            CpuInfoBean cpuInfoBean2 = new CpuInfoBean(procStatFirstLine);
            BigDecimal total2 = cpuInfoBean2.getCpuTotal();
            BigDecimal total = total2.subtract(total1);
            BigDecimal idle = cpuInfoBean2.getIdle().subtract(cpuInfoBean1.getIdle());
            BigDecimal pcpu = new BigDecimal(100).multiply(total.subtract(idle)).divide(total, 0, BigDecimal.ROUND_HALF_UP);
            br.close();
            return pcpu;
        } catch (Exception e) {
            log.info(e.toString());
            return new BigDecimal(0);
        }

    }

    // 获取内存使用率
    public static BigDecimal getMemory() {
        OperatingSystemMXBean osmxb = (OperatingSystemMXBean) ManagementFactory.getOperatingSystemMXBean();
        BigDecimal total = new BigDecimal(osmxb.getTotalPhysicalMemorySize());
        BigDecimal free = new BigDecimal(osmxb.getFreePhysicalMemorySize());
        BigDecimal pmem = new BigDecimal(100).multiply(total.subtract(free)).divide(total, 0, BigDecimal.ROUND_HALF_UP);
        return pmem;
    }

    /**
     * 获取系统负载:top的15分钟平均值/(逻辑cpu核数*0.7)
     */
    public static BigDecimal getLoad() {
        try {
            Runtime r = Runtime.getRuntime();
            BigDecimal cpuPerformance = new BigDecimal(0.7).multiply(new BigDecimal(r.availableProcessors()));
            Process pro = r.exec(LOAD_COMMAND);
            BufferedReader br = new BufferedReader(new InputStreamReader(pro.getInputStream()));
            String topLoad = br.readLine();
            BigDecimal load = new BigDecimal(topLoad.substring(topLoad.lastIndexOf(" ")+1));
            BigDecimal pload = new BigDecimal(100).multiply(load).divide(cpuPerformance, 0, BigDecimal.ROUND_HALF_UP);
            br.close();
            pro.destroy();
            return pload;
        } catch (Exception e) {
            log.info(e.toString());
            return new BigDecimal(0);
        }
    }
}

1.2 Backing beans

• The construction method is a bit verbose, if you have a better way, please leave a message

import lombok.Data;

import java.math.BigDecimal;
import java.util.StringTokenizer;

@Data
public class CpuInfoBean {
    // /proc/stat中cpu数据10元组
    private BigDecimal user, nice, system, idle, iowait, irq, softirq, stealstolen, guest, guest_nice;

    public CpuInfoBean(StringTokenizer procStatFirstLine) {
        procStatFirstLine.nextToken();
        this.user = procStatFirstLine.hasMoreTokens() ? new BigDecimal(procStatFirstLine.nextToken()) : BigDecimal.ZERO;
        this.nice = procStatFirstLine.hasMoreTokens() ? new BigDecimal(procStatFirstLine.nextToken()) : BigDecimal.ZERO;
        this.system = procStatFirstLine.hasMoreTokens() ? new BigDecimal(procStatFirstLine.nextToken()) : BigDecimal.ZERO;
        this.idle = procStatFirstLine.hasMoreTokens() ? new BigDecimal(procStatFirstLine.nextToken()) : BigDecimal.ZERO;
        this.iowait = procStatFirstLine.hasMoreTokens() ? new BigDecimal(procStatFirstLine.nextToken()) : BigDecimal.ZERO;
        this.irq = procStatFirstLine.hasMoreTokens() ? new BigDecimal(procStatFirstLine.nextToken()) : BigDecimal.ZERO;
        this.softirq = procStatFirstLine.hasMoreTokens() ? new BigDecimal(procStatFirstLine.nextToken()) : BigDecimal.ZERO;
        this.stealstolen = procStatFirstLine.hasMoreTokens() ? new BigDecimal(procStatFirstLine.nextToken()) : BigDecimal.ZERO;
        this.guest = procStatFirstLine.hasMoreTokens() ? new BigDecimal(procStatFirstLine.nextToken()) : BigDecimal.ZERO;
        this.guest_nice = procStatFirstLine.hasMoreTokens() ? new BigDecimal(procStatFirstLine.nextToken()) : BigDecimal.ZERO;
    }

    public BigDecimal getCpuTotal() {
        return user.add(nice).add(system).add(idle).add(iowait).add(irq).add(softirq).add(stealstolen).add(guest).add(guest_nice);
    }
}

2 questions

2.1 java uses Runtime.exec to execute linux commands unsuccessfully

2.1.1 Problem description

Failed to obtain the number of cpu logical cores, the command is "cat /proc/cpuinfo | grep processor | wc -l"

2.1.2 Cause of the problem

• The command may fail because of the pipe character "|". I don't know the specifics. If you have any bloggers, please leave a message and reply.
• The blogger replied: Direct execution with exec will cause the command to be executed as a process, and the results cannot be queried. But after using sh -c, the command is broken down into three sub-processes through the pipe symbol, and executes "cat /proc/cpuinfo", "grep processor", and "wc -l" respectively, and the result of the previous process passes through the pipe as the next one The input of the process, so as to query the specific results.

2.1.3 Solution

解决方式一（采用，有局限性）：
    用java自带工具实现Runtime.getRuntime().availableProcessors()
解决方式二：
    命令参数改为数组
    String[] command = {"sh", "-c", "cat /proc/cpuinfo | grep processor | wc -l"};
    或 String[] command = { "/bin/sh", "-c", "cat /proc/cpuinfo | grep processor | wc -l"};