需要实现看门狗功能，定时检测另外一个程序是否在运行，使用 crontab 仅可以实现检测程序是否正在运行，无法做到扩展，如：手动重启、程序升级(如果只需要实现自动升级功能可以使用 inotify)等功能；最后决定使用 Spring Boot 调用 Shell 脚本来实现

一、脚本

1.1 启动脚本

#!/bin/bashps -ef | grep "demo-app-0.0.1-SNAPSHOT.jar" | grep -v "grep"if [ "$?" -eq 0 ]then# sleepecho $(date "+%Y-%m-%d %H:%M:%S") "process already started!"elsenohup java -jar -server /project/watchdog/demo-app-0.0.1-SNAPSHOT.jar &echo $(date "+%Y-%m-%d %H:%M:%S") "process has been started!"fi

1.2 重启脚本

#!/bin/bashpid=`ps -ef | grep "demo-app-0.0.1-SNAPSHOT.jar" | grep -v "grep" | awk '{print $2}'`for id in $piddo kill -9 $id echo "killed $id"donenohup java -jar -server /project/watchdog/demo-app-0.0.1-SNAPSHOT.jar &echo $(date "+%Y-%m-%d %H:%M:%S") "process has been restarted!"

二、功能实现

将脚本放置在程序的资源目录下，每次程序启动时将脚本读取到指定位置，然后再通过定时任务执行脚本

配置内容：

shell: directory: /project/watchdog startupFileName: startup.sh restartFileName: restart.sh@Configuration@ConfigurationProperties(prefix = "shell")public class ShellProperties { private String directory; private String startupFileName; private String restartFileName; public String getFullName(String fileName) { return directory + File.separator + fileName; }}

2.1 启动时将脚本读取到指定位置

@Componentpublic class InitRunner implements CommandLineRunner { @Autowired private ShellProperties shellProperties; @Autowired ResourceLoader resourceLoader; @Override public void run(String... args) throws Exception { generateFile(shellProperties.getStartupFileName()); generateFile(shellProperties.getRestartFileName()); } private void generateFile(String fileName) throws IOException { String fileFullName = shellProperties.getFullName(fileName); File file = new File(fileFullName); if(file.exists()) { return; } // 如果文件已存在，FileWriter 会先删除再新建 FileWriter fileWriter = new FileWriter(fileFullName); Resource resource = resourceLoader.getResource("classpath:" + fileName); InputStream inputStream = resource.getInputStream(); InputStreamReader inputStreamReader = new InputStreamReader(inputStream); BufferedReader bufferedReader = new BufferedReader(inputStreamReader); String data; while ((data = bufferedReader.readLine()) != null) { fileWriter.write(data + "\n"); } bufferedReader.close(); inputStreamReader.close(); inputStream.close(); fileWriter.close(); // 设置权限，否则会报 Permission denied file.setReadable(true); file.setWritable(true); file.setExecutable(true); }}

2.2 定时任务定时任务执行脚本

@Componentpublic class ShellTask { private static final Logger logger = LoggerFactory.getLogger(ShellTask.class); @Autowired private ShellProperties shellProperties; @Scheduled(cron = "0/10 * * * * ? ") public void start() throws IOException { executeShell(shellProperties.getStartupFileName()); } private void executeShell(String fileName) throws IOException { String fileFullName = shellProperties.getFullName(fileName); File file = new File(fileFullName); if(!file.exists()) { logger.error("file {} not existed!", fileFullName); return; } ProcessBuilder processBuilder = new ProcessBuilder(fileFullName); processBuilder.directory(new File(shellProperties.getDirectory())); Process process = processBuilder.start();// String input;// BufferedReader stdInput = new BufferedReader(new InputStreamReader(process.getInputStream()));// BufferedReader stdError = new BufferedReader(new InputStreamReader(process.getErrorStream()));// while ((input = stdInput.readLine()) != null) {// logger.info(input);// }// while ((input = stdError.readLine()) != null) {// logger.error(input);// } int runningStatus = 0; try { runningStatus = process.waitFor(); } catch (InterruptedException e) { logger.error("shell", e); } if(runningStatus != 0) { logger.error("failed."); }else { logger.info("success."); } }}

2.3 扩展

本例只实现了定时检测程序是否运行，如果没有运行则启动程序；如有需要可以添加接口，调用接口重启程序；或者添加定时任务定时检测程序是否有更新，如果有更新则下载新的 jar 包然后重启程序

看门狗程序自己可以使用 crontab 定时检测是否正在运行，模仿上面的启动脚本编写看门狗的启动脚本，然后添加定时任务：

crontab -e*/10 * * * * /project/watchdog/watchdog.shsudo systemctl reload crond.service

完整代码：GitHub

参考：java去调用并执行shell脚本以及问题总结

总结

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