[Java知识库]系统内存超过比例打印JVM日志

import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Component;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;
import java.nio.charset.StandardCharsets;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;

/**
 * @author： guanglai.zhou
 * @date： 2022/4/28 18:49
 */
@Component
public class JvmMonitor implements ApplicationListener<ContextRefreshedEvent> {

    private static final Logger logger = LoggerFactory.getLogger(JvmMonitor.class);

    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
        int pid = getProcessID();
        String[] cmds = new String[]{
                "jps -lvm",
                "jmap -heap " + pid,
                "jmap -histo " + pid + " |head -20",
                "jcmd " + pid + " GC.class_histogram | head -20",
                "jstack " + pid
        };
        ScheduledExecutorService scheduledExecutorService = Executors.newSingleThreadScheduledExecutor(new ThreadFactory() {
            @Override
            public Thread newThread(Runnable r) {
                Thread thread = new Thread(r);
                thread.setName("jvm-schedule-monitor");
                return thread;
            }
        });
        scheduledExecutorService.scheduleWithFixedDelay(new Runnable() {
            @Override
            public void run() {
                // 单位为M
                long freeMemory = Runtime.getRuntime().freeMemory();
                // 最大内存
                long maxMemory = Runtime.getRuntime().maxMemory();

                String printRatio = System.getProperty("jvm.print.memory.ratio");
                if (StringUtils.isBlank(printRatio) || printRatio.matches("\\d+\\.\\d+")) {
                    // 默认值为0.2 如果JVM内存只剩余了20% 就会打印日志
                    printRatio = "0.2";
                }
                double jvmPrintRatio = Double.parseDouble(printRatio);
                if (freeMemory < maxMemory * 0.2) {
                    monitorSystem(cmds);
                }
            }
        }, 1, 10 * 60, TimeUnit.SECONDS);
    }

    public static void monitorSystem(String[] cmds) {
        for (String cmd : cmds) {
            try {
                String result = execCmd(cmd);
                logger.info("{}[root@60 ~]#{}{}{}", System.lineSeparator(), cmd, System.lineSeparator(), result);
            } catch (IOException | InterruptedException e) {
                logger.error("执行系统命令" + cmd + "报错:" + e.getMessage(), e);
            }
        }
    }


    private static String execCmd(String cmd) throws IOException, InterruptedException {
        Process ps = Runtime.getRuntime().exec(cmd);
        BufferedReader br = new BufferedReader(new InputStreamReader(ps.getInputStream(), StandardCharsets.UTF_8));
        StringBuilder result = new StringBuilder();
        String line;
        while ((line = br.readLine()) != null) {
            result.append(line).append(System.lineSeparator());
        }
        br.close();
        ps.waitFor();
        return result.toString();
    }

    private static int getProcessID() {
        RuntimeMXBean runtimeMXBean = ManagementFactory.getRuntimeMXBean();
        return Integer.valueOf(runtimeMXBean.getName().split("@")[0]);
    }
}

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