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)

return null;
        }
        return serviceInfo.getParameter(key);
    }
    public Map<String, String> getParameters(String serviceKey) {
        ServiceInfo serviceInfo = services.get(serviceKey);
        if (serviceInfo == null) {
            return Collections.emptyMap();
        }
        return serviceInfo.getAllParams();
    }
    public String getServiceString(String protocolServiceKey) {
        if (protocolServiceKey == null) {
            return null;
        }
        ServiceInfo serviceInfo = services.get(protocolServiceKey);
        if (serviceInfo == null) {
            return null;
        }
        return serviceInfo.toString();
    }
    @Override
    public String toString() {
        return "metadata{" +
                "app='" + app + "'," +
                "revision='" + revision + "'," +
                "services=" + services +
                "}";
    }
    public static class ServiceInfo implements Serializable {