At the CA Microservices Conference, Vijay Alagarasan spoke about some anti-patterns. I have reworded them to be patterns to follow and added a couple of my own thoughts.
Automation is Litmus
The litmus test on whether you can handle microS is if you can automate. Automated testing and deployment is key to microS, but beyond that if what you have is not regular enough or so eccentric that automation is not possible then you either still in R&D land or you simply are not ready yet. You do not need to automate everything, but if there is something about the software that inhibits automation then that will be a problem for stability, scale, or your own sanity when problems occur.
Centrally Manage Config
Design a configuration manger. There should be one server (not literally one, you're allowed redundancy) that can send configuration changes to your services. If you don't start from day one then you will be unable to control scale. The time to centrally manage the configuration of a service is when you deploy the first instance. Once you are running 15 instances of it, you are likely to miss an instance when you need to change a setting on it. Just think to the last time you were debugging an issue that was intermittent and you checked everything only to finally discover that one of the servers was configured differently. Sometimes it is obvious, but given that you always assume someone was diligent and set them all up identically you can often overlook that sort of bug. Avoid the headache and always manage configuration centrally.
The one argument you can make against central config is security. As I write this it does occur to me that a malicious actor who merely wanted to reek havoc on your network could do it through the config server, but that is more the case of a disgruntled employee with system knowledge. Chances are your hack is going to be by someone that wants to find their way to something valuable and changing something like a rate limit on an API is not likely to help much. Maybe talk to your security officer about this if you are concerned.
API Gateway
An API Gateway has many benefits. It can reveal a lot about network traffic and help to control it with things like caching, routing, throttling (limiting particular calls), and authorization. It can also help you transition from one version of a service to a another by slowly moving traffic to the new one. For example: consumer A is routed to version 2, but all other consumers are routed to version 1. Then consumer B moves to version 2 and so on. A good version strategy allows you to to introduce new versions of a service with a minimum of risk.
However all of the stability a gateway can offer can be reversed through misuse. Every bit of business logic that works its way into the gateway is a potential production issue. The point of the gateway is to abstract you from the business logic so that you can change your business logic carefully (as mentioned with transitioning to a new version of a service). If the business logic is in the gateway then you cannot change that logic without risking all of your traffic being negatively impacted. There will be some business logic in your gateway, but assume anything you put in there may need to be changed and cause a full system outage. Each IF statement should be put in place with that realization.
I'm unfamiliar with these products, but CA Layer 7 and AWS Mobile Gatway are examples of API Gateways.
Question Every Layer
Abstraction is a useful tool, but it needs to be used purposefully. For instance, having a policy to abstract the connection to every database is not good. Each use of abstraction should be for a strong reason about that particular case. Unnecessary layers should be avoided. A coworker told me "no one ever wants to be the middle man" and you should think of layers like middle men. Most of the objections to middle men are the same reason you don't want extra layers in your software. They introduce complexity and the potential for translation issues, they constrain your message into their terms (admitidly this can be a pro), and they consume resources. People would always rather go to the source, but they will put up for a middle man when there's a good reason. Don't just have an extra layer in place like in Office Space.
Do not separate your layers by bussiness logic, data access, or orchestration. One layer should likely embrace all three of these things. The boundaries of a service should be based on a business solution and not a technical one. You are building services to solve business needs. Being able to switch your database out to another one should not be the guiding star by which you design your services. If you have a good version strategy then that should be all you need for technical changes.
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