每次应用重启，都会在 /dubbo/metadata/${appName} 下生成一个版本号。经过调试，发现在每次计算 revison， 会连同  pid 和 timestamp 一起计算。这样是不是有问题呢？

![image](https://user-images.githubusercontent.com/24663965/125059185-a1178700-e0dd-11eb-8271-0243d59d30b6.png)

public static final MetadataInfo EMPTY = new MetadataInfo();
    private String app;
    private String revision;
    private Map<String, ServiceInfo> services;
    
    private transient Map<String, String> extendParams;
    private transient AtomicBoolean reported = new AtomicBoolean(false);
    public MetadataInfo() {
        this(null);
    }
    public MetadataInfo(String app) {
        this(app, null, null);
    }
    public MetadataInfo(String app, String revision, Map<String, ServiceInfo> services) {
        this.app = app;
        this.revision = revision;
        this.services = services == null ? new HashMap<>() : services;
        this.extendParams = new HashMap<>();
    }
    public void addService(ServiceInfo serviceInfo) {
        if (serviceInfo == null) {
            return;
        }
        this.services.put(serviceInfo.getMatchKey(), serviceInfo);
        markChanged();
    }
    public void removeService(ServiceInfo serviceInfo) {
        if (serviceInfo == null) {
            return;