[BUG] Use the multi-registry feature with Nacos registry that set namingLoadCacheAtStart=true, the cache of NacosNamingService will overwrite each other

[plusmancn]

• I have searched the issues of this repository and believe that this is not a duplicate.
• I have checked the FAQ of this repository and believe that this is not a duplicate.

Environment

• Dubbo version: build from mater branch
• Operating System version: Mac OSX
• Java version: 1.8

Steps to reproduce this issue

When I use the multi-registry feature of Dubbo with setting namingLoadCacheAtStart=true(default is also true in Dubbo), the cache of NacosNamingService will overwrite each other.
If two registries have different services, some of the services will be lost because of overwriting.

For example, we have settings as below:

<dubbo:registry id="registryDev" address="nacos://127.0.0.1:8849?namingLoadCacheAtStart=true"/>
<dubbo:registry id="registryTest" address="nacos://127.0.0.1:8848?namingLoadCacheAtStart=true"/>

If registryStable overwrites registryDev, the consumer can't find the GreetingService in registryDev.

Expected Result

The different registry has different cache folder, so the cache will not overwrite each other.

PS: zookeeper works well with multi-registry feature of Dubbo.

Actual Result

The cache of NacosNamingService will overwrite each other.
If two registries have different services, some of the services will be lost because of overwriting.

[plusmancn]

Final Solution

• Step1: Nacos support User-Defined cacheDir

I have submitted PRs to both Nacos Client v1.x and v2.x, see: alibaba/nacos#5747.
It will be released around July 2021.

• Step2: Dubbo specify the cacheDir of Nacos

dubbo/dubbo-registry/dubbo-registry-nacos/src/main/java/org/apache/dubbo/registry/nacos/util/NacosNamingServiceUtils.java

Lines 145 to 155 in ff50f91

	private static void setProperties(URL url, Properties properties) {
	putPropertyIfAbsent(url, properties, NACOS_NAMING_LOG_NAME);
	// @since 2.7.8 : Refactoring
	// Get the parameters from constants
	Map<String, String> parameters = url.getParameters(of(PropertyKeyConst.class));
	// Put all parameters
	properties.putAll(parameters);
	putPropertyIfAbsent(url, properties, NAMING_LOAD_CACHE_AT_START, "true");
	}

Try to Calculate the cacheDir path of Nacos Registry automatically, and then set it by properties.
The rule of generating cacheDir may base on Registry.id, Registry.address and etc.
The PR will be submitted once the Nacos 1.4.3 release.

Temporary Solution

Just set namingLoadCacheAtStart to false as follow mannully:

<dubbo:registry id="registryDev" address="nacos://127.0.0.1:8849?namingLoadCacheAtStart=false"/>
<dubbo:registry id="registryTest" address="nacos://127.0.0.1:8848?namingLoadCacheAtStart=false"/>

[plusmancn]

How to use it.

From Dubbo 3.0.2（which Nacos dependency 2.0.2), just set namingCacheRegistryDir to different sub dir, if you want to avoid NamingCache overwriting each other, for example:

<dubbo:registry id="registryDev" address="nacos://127.0.0.1:8849?namingCacheRegistryDir=sub1"/>
<dubbo:registry id="registryTest" address="nacos://127.0.0.1:8848?namingCacheRegistryDir=sub2"/>

[AlbumenJ]

@plusmancn Could you please help to add some description related with this issue to apache/dubbo-website ?

[plusmancn]

@plusmancn Could you please help to add some description related with this issue to apache/dubbo-website ?

I will