maxucheng0 opened a new issue #2574:
URL: https://github.com/apache/servicecomb-java-chassis/issues/2574
**Describe the bug**
背景：当前正在使用servicecomb-java-chassis 2.1.5版本，之前使用servicecomb-java-chassis
1.3.1版本，在1.3.1版本中，MicroserviceVersions会定时（30s）触发pullInstances来更新实例缓存，在2.1.5发现仅能通过实例更新事件触发MicroserviceVersions中的缓存更新，如果更新事件丢失，且后续没有实例新的更新事件，缓存一致性无法保证。
现象：实例注册后更新实例属性成功，在其他服务实例中进行服务间调用时指定transactionControl仅调用存在对应属性的服务实例，Load
balancer报错无法找到可用实例。
原因分析：MicroserviceVersions在初始化时先进行了pullInstances之后将此microserviceVersions放入versionsByName的map中，在执行pullInstances时如果收到了更新事件，会触发MicroserviceManager里面的全量更新方法，此方法是通过遍历versionsByName中的MicroserviceVersions进行pullInstances的调用，此时之前创建的microserviceVersions未放入versionsByName中，导致丢失此次更新事件，之后缓存无法恢复，服务间调用持续失败。
_MicroserviceManager.java_
```
public MicroserviceVersions getOrCreateMicroserviceVersions(String
microserviceName) {
MicroserviceVersions microserviceVersions =
versionsByName.get(microserviceName);
if (microserviceVersions == null) {
synchronized (lock) {
microserviceVersions = versionsByName.get(microserviceName);
if (microserviceVersions == null) {
microserviceVersions = new MicroserviceVersions(appManager, appId,
microserviceName);
microserviceVersions.pullInstances();
versionsByName.put(microserviceName, microserviceVersions);
}
}
}
tryRemoveInvalidMicroservice(microserviceVersions);
return microserviceVersions;
}
...
public void pullInstances() {
for (MicroserviceVersions microserviceVersions :
versionsByName.values()) {
microserviceVersions.pullInstances();
tryRemoveInvalidMicroservice(microserviceVersions);
}
}
public void onMicroserviceInstanceChanged(MicroserviceInstanceChangedEvent
changedEvent) {
for (MicroserviceVersions microserviceVersions :
versionsByName.values()) {
microserviceVersions.onMicroserviceInstanceChanged(changedEvent);
tryRemoveInvalidMicroservice(microserviceVersions);
}
}
```
解决建议：当前可以通过先将初始化后的MicroserviceVersions放入MicroserviceManager的versionsByName中，之后再进行pullInstances，由于阻塞pullInstances的原因是因为流程中的setInstances中存在锁，不一定可以完全保证先执行首次拉取结果的set，再进行更新事件的set，所以仍需要定时pullInstances的操作。
**To Reproduce**
复现方法：通过判断服务名在创建对应MicroserviceVersions缓存时sleep
30s，在sleep期间进行实例属性的更新，之后进行服务间调用时指定更新后的实例属性。
_MicroserviceVersions.java_
```
private void setInstances(List<MicroserviceInstance> pulledInstances, String
rev) {
if ("Service03".equals(getMicroserviceName())) {
try {
TimeUnit.SECONDS.sleep(30);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
synchronized (lock) {
MergedInstances mergedInstances = mergeInstances(pulledInstances,
instances);
instances = mergedInstances.instanceIdMap.values();
// clear cache
versions.entrySet().forEach(versionEntry ->
versionEntry.getValue().setInstances(new ArrayList<>()));
for (Entry<String, List<MicroserviceInstance>> entry :
mergedInstances.microserviceIdMap.entrySet()) {
// ensure microserviceVersion exists
versions.computeIfAbsent(entry.getKey(),
microserviceId -> createMicroserviceVersion(microserviceId,
entry.getValue()))
.setInstances(entry.getValue());
}
for (MicroserviceVersionRule microserviceVersionRule :
versionRules.values()) {
microserviceVersionRule.update(versions, instances);
}
revision = rev;
}
}
```
**Expected behavior**
服务间调用可以成功。
**Platform And Runtime (please complete the following information):**
环境无差别，稳定复现
**Additional context**
无
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