make the seed for YamlSeedConfigPersistence configurable

[cgardens]

Relates to #6334

What

• We want the cloud app to use a different seed than OSS. This change makes it so that it possible to customize where YamlSeedConfigPersistence pulls the seed from. My understanding is that changing this class to take in the correct seed should completely solve the issue of the cloud operating on a different index. I will still need to, as a one off, prune out the connectors in cloud that shouldn't be there.
• @tuliren curious if you think this is a good approach or given that it needs an argument now, I should move to dependency injection.

Recommended reading order

1. YamlSeedConfigPersistence.java

[michel-tricot]

I understand why you need to do that but this complex object lifecycle has some code smell.

Why is the YamlSeedConfigPersistence a singleton? Are we ever using it without injecting?

[tuliren]

Now that this class can be constructed differently, I think it should not be a singleton any more.

[cgardens]

cool. thanks. this was my intuition too.

[tuliren]

Can be we have some smiple helper method to construct this class, like YamlSeedConfigPersistence.getDefault(), which automatically use the default resource class? Otherwise people won't remember which class to use.

[tuliren]

This initialize method no longer exists. This line can be deleted. Otherwise code cannot compile.

Suggested change

YamlSeedConfigPersistence.initialize(YamlSeedConfigPersistence.DEFAULT_SEED_DEFINITION_RESOURCE_CLASS);

[tuliren]

I think it's better to ditch the singleton pattern and combine the initialize and get method into the following methods:

public YamlSeedConfigPersistence(final Class<?> seedDefinitionsResourceClass) {
  this.allSeedConfigs = ImmutableMap.<SeedType, Map<String, JsonNode>>builder()
    .put(SeedType.STANDARD_SOURCE_DEFINITION, getConfigs(seedDefinitionsResourceClass, SeedType.STANDARD_SOURCE_DEFINITION))
    .put(SeedType.STANDARD_DESTINATION_DEFINITION, getConfigs(seedDefinitionsResourceClass, SeedType.STANDARD_DESTINATION_DEFINITION))
    .build();
}

public static YamlSeedConfigPersistence getDefault() {
  return new YamlSeedConfigPersistence(DEFAULT_SEED_DEFINITION_RESOURCE_CLASS);
}

public static YamlSeedConfigPersistence get(final Class<?> seedDefinitionsResourceClass) {
  return new YamlSeedConfigPersistence(seedDefinitionsResourceClass);
}

Static class variables should preferrably be final.

[tuliren]

This test shows a good example why the static class variable should not be modified. It is very confusing that we need to call initialize in the setup method first before calling the get here. No one will remember to do this until they get the exception message.

[cgardens]

thanks for the review. I agree with both of you. Updated PR to reflect it. @tuliren ready for another review when you are.

[tuliren]

This initialize method no longer exists. This line can be deleted. Otherwise code cannot compile.

Suggested change

YamlSeedConfigPersistence.initialize(YamlSeedConfigPersistence.DEFAULT_SEED_DEFINITION_RESOURCE_CLASS);