naming selectInstances method doesn't subscribe when loadCacheAtStart=true

[nkorange]

Describe the bug

naming selectInstances method doesn't subscribe when loadCacheAtStart=true

Expected behavior

naming selectInstances method does subscription when loadCacheAtStart=true

Actually behavior

naming selectInstances method doesn't subscribe when loadCacheAtStart=true

How to Reproduce
Steps to reproduce the behavior:

App1:

public class App1 {

    public static void main(String[] args) throws Exception {
        NamingService namingService = NamingFactory.createNamingService("127.0.0.1:8848");
        namingService.registerInstance("test.peterzhu.0", "2.2.2.2", 8080);
        Thread.sleep(100000000L);
    }
}

App2:

public class App2 {

    public static void main(String[] args) throws Exception {
        Properties properties = new Properties();
        properties.put("serverAddr", "127.0.0.1:8848");
        properties.put("namingLoadCacheAtStart", "true");
        NamingService namingService = NamingFactory.createNamingService(properties);
        namingService.registerInstance("test.peterzhu.0", "1.1.1.1", 8080);

        while (true) {
            System.out.println(namingService.selectInstances("test.peterzhu.0", true));
            Thread.sleep(3000L);
        }
    }
}

1. Run App2
2. Stop App2, and check the local cache file where there should be cached instance list containing 1.1.1.1.
3. Run App2
4. Run App1, you can find App2 always prints 1.1.1.1, without the new instance 2.2.2.2.

Desktop (please complete the following information):

• OS: MacOS
• Version Nacos Server 2.1.2, Nacos Client 2.2.2
• Module naming
• SDK original

Additional context

The bug is in selectInstances method that if local cache is not empty, the subscription would be skipped. Similar issue is also found in method selectOneHealthyInstance

[linzhihan]

i wanna take a look into this issue

[WindSearcher]

can i try it？

[KomachiSion]

Of cource, you can.

[WindSearcher]

I found that Mac OS can only reproduce the above situation in the same version environment, win11 not. I think the key is whether the service information changes are updated to the serviceInfoMap when the service instance is registered.

[stone-98]

@WindSearcher 老哥，我再windows10复现出来了，这个和系统应该没关系，可以参考参考ISSUE#7550

[Bo-Qiu]

Thank you all for the information provided. I happen to have some free time recently to deal with some issues, so I've submitted a PR to fix this problem.