Alanxtl commented on code in PR #3685:
URL: https://github.com/apache/dubbo-go/pull/3685#discussion_r3818849769
##########
registry/servicediscovery/service_instances_changed_listener_impl.go:
##########
@@ -277,8 +281,23 @@ func GetMetadataInfo(app string, instance
registry.ServiceInstance, revision str
initCache(app)
})
cacheKey := metadataCacheKey(app, registryId, revision)
- if metadataInfo, ok := metaCache.Get(cacheKey); ok {
- return metadataInfo.(*info.MetadataInfo), nil
+ if cached, ok := metaCache.Get(cacheKey); ok {
+ logger.Debugf("[Metadata][Cache] hit app=%s registry=%s
revision=%s host=%s",
+ app, registryId, revision, instance.GetHost())
+ event :=
metricsMetadata.NewMetadataMetricTimeEvent(metricsMetadata.MetadataCache)
+ event.Succ = true
+ event.Attachment[metricsMetadata.TagProviderApp] = app
+ metrics.Publish(event)
+ metadataInfo := cached.(*info.MetadataInfo)
+ if metadataInfo == nil {
+ publishMetadataFetchEvent(app, registryId, revision,
instance.GetHost(),
+ metricsMetadata.SourceCache,
metricsMetadata.StorageTypeCache, metricsMetadata.ResultFailure,
+ perrors.New("typed nil metadata in cache"))
+ return nil, nil
+ }
+ publishMetadataFetchEvent(app, registryId, revision,
instance.GetHost(),
+ metricsMetadata.SourceCache,
metricsMetadata.StorageTypeCache, metricsMetadata.ResultSuccess, nil)
+ return metadataInfo, nil
Review Comment:
`OnEvent` 会先读取 `lstn.revisionToMetadata`。同一 revision 的后续实例命中这个 map 后，不会调用
`GetMetadataInfo`，因此不会上报 `MetadataCache`
hit。多实例场景下，`dubbo_metadata_cache_hit_total / total`
会明显低估真实命中率。建议在这层缓存也埋点，或明确该指标只代表 `metaCache`（磁盘/LRU）缓存。
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