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)

}
        this.services.remove(serviceInfo.getMatchKey());
        markChanged();
    }
    public void removeService(String key) {
        if (key == null) {
            return;
        }
        this.services.remove(key);
        markChanged();
    }
    public String calAndGetRevision() {
        if (revision != null && hasReported()) {
            return revision;
        }
        if (CollectionUtils.isEmptyMap(services)) {
            this.revision = RevisionResolver.getEmptyRevision(app);
        } else {
            StringBuilder sb = new StringBuilder();
            sb.append(app);
            for (Map.Entry<String, ServiceInfo> entry : new TreeMap<>(services).entrySet()) {
                sb.append(entry.getValue().toDescString());
            }
            this.revision = RevisionResolver.calRevision(sb.toString());
        }
        return revision;
    }
    public void setRevision(String revision) {
        this.revision = revision;
    }