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/bash ps -ef | grep "demo-app-0.0.1-SNAPSHOT.jar" | grep -v "grep" if [ "$?" -eq 0 ] then # sleep echo $(date "+%Y-%m-%d %H:%M:%S") "process already started!" else nohup 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/bash
pid=`ps -ef | grep "demo-app-0.0.1-SNAPSHOT.jar" | grep -v "grep" | awk '{print $2}'`
for id in $pid
do
kill -9 $id
echo "killed $id"
done
nohup 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;
/* getter & setter */
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
@Component
public 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
@Component
public 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.sh sudo systemctl reload crond.service
完整代码：GitHub
