Question

我在Linux上有一个多线程应用程序。我通过解析/ net / proc / tcp文件来推断主叫用户的ID。基本上，操作系统会在系统文件中添加本地/远程地址和端口信息，我们尝试将其与http套接字详细信息进行匹配。

 private String identifyCaller(HttpServletRequest httpServletRequest) {
        IdService idService = new IdService();
        OptionalInt uid = idService.getUID(
                httpServletRequest.getLocalAddr(),
                httpServletRequest.getLocalPort(),
                httpServletRequest.getRemoteAddr(),
                httpServletRequest.getRemotePort());
       ...

和IdService类类似

class IdService {

    private static Pattern pattern = Pattern.compile("\\s*\\d+: ([0-9A-Fa-f]+):([0-9A-Fa-f]+) ([0-9A-Fa-f]+):([0-9A-Fa-f]+) ([0-9A-Fa-f]{2}) [0-9A-Fa-f]+:[0-9A-Fa-f]+ [0-9A-Fa-f]+:[0-9A-Fa-f]+ [0-9A-Fa-f]+\\s+([0-9]+).+");

    private final String ipV4Path;
    private final String ipV6Path;

    public IdService() {
        this.ipV4Path = Constants.PROC_NET_TCP_PATH;
        this.ipV6Path = Constants.PROC_NET_TCP6_PATH;
    }


    public OptionalInt getUID(String localAddr, int localPort, String remoteAddr, int remotePort) {

        OptionalInt uid;
        try (BufferedReader br = new BufferedReader(new FileReader(ipV4Path))) {
            String line;
            while ((line = br.readLine()) != null) {
                uid = getUID(line, localPort, remotePort, remoteAddr); 

                if (uid.isPresent()) {
                    return uid;
                }
            }
        } catch (IOException e) {
            log.error("Exception reading {} file. ", ipV4Path, e);
            // Handle
        }

private OptionalInt getUID(String line, String remoteAddr, int reqLocalPort, int reqRemotePort) {
        Matcher matcher = pattern.matcher(line);
        if (!matcher.matches()) {
            return OptionalInt.empty();
        }
        int count = matcher.groupCount();
        ... 
        // More rules and if match then returns a matched field 
   }

}

我看到，除非我使用IdSevice的新实例，否则对UID的扫描将返回空Optional（当前套接字不匹配）。 “ / net / proc / tcp”中的内容发生了变化，但是我想知道是什么导致此线程不安全。所有工作似乎都发生在局部线程变量上，因此我以前使用的是单例对象，但结果不正确。成员变量是常量String对象，唯一的静态对象是最终成员。那么，什么导致线程不安全呢？

为什么这不是线程安全的？

0 个答案: