Feature: choose first subnet in selection for single instance broker deployments

[jayalfredprufrock]

Thanks for the super useful construct! Saved me lots of time :)

While playing with it, I came across the error: Specify a single subnet in [SINGLE_INSTANCE] deployment mode..

It's probably not that uncommon to have multiple isolated subnets across availability zones, but still deploy only a single instance broker (perhaps to manage cost in development environments). Having to manually construct a subnet selection to contain exactly one subnet is a little awkward. Other official constructs seem to allow a larger subnet selection and (presumably) just choose the first one - at least I've never hit an error like this before. Anyways, would be great if this construct could handle this case more gracefully somehow.

Here is what I need to do now:

const isolatedSubnets = this.vpc.selectSubnets({
      subnetType: SubnetType.PRIVATE_ISOLATED,
});

const rmqBroker = new RabbitMqBrokerInstance(this, 'rmq-broker', {
       vpc: this.vpc,
       vpcSubnets: { subnets: [isolatedSubnets.subnets[0]] },
       ...
}

It's actually a little more complicated in my case, since I have to switch between the single and cluster constructs depending on some configuration. Not a huge deal but wanted to mention in case somebody else would find this useful. Thanks again!

[swimming-potato]

Hi, @jayalfredprufrock thanks for your feedback. We are happy to hear that our work is helping others :) We will discuss the possible options and get back to you next week.