需要實現看門狗功能，定時檢測另外一個程序是否在運行，使用 crontab 僅可以實現檢測程序是否正在運行，無法做到擴展，如：手動重啟、程序升級(如果只需要實現自動升級功能可以使用 inotify)等功能；最后決定使用 Spring Boot 調用 Shell 腳本來實現

一、腳本

1.1 啟動腳本

#!/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 重啟腳本

#!/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、功能實現

將腳本放置在程序的資源目錄下，每次程序啟動時將腳本讀取到指定位置，然后再通過定時任務執行腳本

配置內容：

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; /* getter & setter */ public String getFullName(String fileName) { return directory + File.separator + fileName; }}

2.1 啟動時將腳本讀取到指定位置

@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 會先刪除再新建 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(); // 設置權限，否則會報 Permission denied file.setReadable(true); file.setWritable(true); file.setExecutable(true); }}

2.2 定時任務定時任務執行腳本

@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 擴展

本例只實現了定時檢測程序是否運行，如果沒有運行則啟動程序；如有需要可以添加接口，調用接口重啟程序；或者添加定時任務定時檢測程序是否有更新，如果有更新則下載新的 jar 包然后重啟程序

看門狗程序自己可以使用 crontab 定時檢測是否正在運行，模仿上面的啟動腳本編寫看門狗的啟動腳本，然后添加定時任務：

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

完整代碼：GitHub

參考：java去調用并執行shell腳本以及問題總結

總結

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