Add support for group and topic prefixes

[AndriiLab]

Problem
We have multiple instances of the app, which deployed to AWS in different VPCs but in the same region. In this scenario, isolation works perfectly except for SNS and SQS, which are shared within the region.

Proposed solution
Add to CapOptions prefixes for topic (TopicNamePrefix ) and group (GroupNamePrefix ) names to make these parameters unique for each application instance. These parameters are optional, and if not defined the behavior will remain unchanged.

[yang-xiaodong]

Hello,

Thanks for your PR,

Since GroupName is customizable, so I think it is redundant to provide GroupNamePrefix

I think it is reasonable to provide TopicNamePrefix

[roman-bezmen]

@yang-xiaodong At the moment it is a bit fussy overriding the way how the group name constructs. For simple cases like providing prefixes to host multiple instances within the same infrastructure, it would be more pleasant to have a consistent way to set up prefixes for both queues and topics, even if there is an alternative way. What are your concerns?

[yang-xiaodong]

What I think is that providing more configuration items will complicate the beginner and keep it simple.

Do as you say at present we have the configuration items DefaultGroup and GroupNamePrefix, In fact, the name of DefaultGroup should be rename to GroupName so that users can know what happened.

[yang-xiaodong]

As described in the comments, rename DefaultGroup to GroupName seemed more appropriate

[AndriiLab]

Currently, we configure GroupNamePrefix via overriding method in ConsumerServiceSelector.SetSubscribeAttribute:

    public class PrefixedConsumerServiceSelector : ConsumerServiceSelector
    {
        private readonly string _prefix;

        public PrefixedConsumerServiceSelector(IServiceProvider serviceProvider, string prefix)
            : base(serviceProvider)
        {
            _prefix = prefix;
        }

        protected override void SetSubscribeAttribute(TopicAttribute attribute)
        {
            base.SetSubscribeAttribute(attribute);
            if (!string.IsNullOrEmpty(_prefix))
            {
                attribute.Group = $"{_prefix}.{attribute.Group}";
            }
        }
     }

And then in Startup.cs:

    services.AddCap(c => ...);
    services.TryRemove<IConsumerServiceSelector>();
    services.TryAddSingleton<IConsumerServiceSelector>(s => new PrefixedConsumerServiceSelector(s, "MyPerfix"));

Possibly, I understand this overring incorrectly, but I think there could be a more simple approach just to add prefix like

    services.AddCap(c => {
        c.GroupNamePrefix = "MyGroupPrefix",
        c.TopicNamePrefix = "MyTopicPrefix"
    });

Since GroupNamePrefix and TopicNamePrefix are not required, the application will behave as usual without these parameters. Similar behavior was implemented for suggested DefaultGroup (GroupName)

[AndriiLab]

Dear @yang-xiaodong,
This feature is very important for us since we use CAP in production. If you have any concerns about releasing this feature for global configuration, I can try to implement it only for the AWS provider.

[yang-xiaodong]

well, I want let you know I will rename options DefaultGroup to GroupName , thanks for your PR

[yang-xiaodong]

Preview version 5.0.0-preview-131679580 released to nuget

[AndriiLab]

Thank you very much, @yang-xiaodong!