Whether or not bug

[YoWuwuuuw]

When writing tests, when the registry center is configured to be similar to "registry. type=file, file", it is found that org.apache.seata.discovery.registry.MultiRegistryFactory will init two identical instances during initialization. Whether this a bug or not?Or does the user not do this at all?

[funky-eyes]

I believe this is a design issue rather than a clear-cut bug. The actual singletons loaded via SPI are the implementations of RegistryProvider, while the RegistryService implementations are constructed through the provide method of RegistryProvider. This architecture results in a new RegistryService instance being created each time the provide method is called.

Therefore, I think we first need to determine whether RegistryService should maintain singleton behavior, rather than continuing with the current multiple-instance pattern.

[YoWuwuuuw]

From the code, no matter how the spi mechanism is implemented, the RegistryService instance returned by provide () is always singletons . Therefore, the above situation is that the List add() the same instance repeatedly, resulting in size 2 (shouldn't be the case), as follows:

    String registryTypes = RegistryType.File.name() + Constants.REGISTRY_TYPE_SPLIT_CHAR + RegistryType.File.name();
    System.setProperty(REGISTRY_TYPE_KEY, registryTypes);

    List<RegistryService> instances = MultiRegistryFactory.getInstances();
    Assertions.assertEquals(2, instances.size());
    Assertions.assertSame(instances.get(1), instances.get(0));

So I think we can add a check before add() to prevent this from happening, in #7345

[funky-eyes]

I was mistaken about the implementation; it is indeed implemented as a singleton return. I think we should change List to Set for simplicity.

[YongGoose]

I was mistaken about the implementation; it is indeed implemented as a singleton return. I think we should change List to Set for simplicity.

The current implementation of RegistryService doesn’t override equals and hashCode.
So if we use a Set, I think logically identical instances could end up being stored as duplicates.