Microservices are coming to a network near you. Forty-one percent (41%) of respondents to our State of Application Delivery 2018 survey told us their organizations were exploring microservices as a result of digital transformation initiatives. With them will come operational and architectural impacts, which makes them an important architectural evolution for NetOps to understand.
Microservices: A Definition
All too often microservices and containers are used interchangeably. It is not merely pedantry to correct this usage, as the former is an application architecture and the latter a delivery model. Containers are used to deliver a variety of infrastructure and operational services as well as microservices. They are prized for their portability; cloud agnosticism is a key characteristic of containers that makes multi-cloud an achievable goal. Nothing in the definition or guiding principles of microservices architectures makes mention of 'containers'. Containers are often used to deploy individual microservices because they are a good operational fit, but they are not required.
Microservices is an architectural style of application design. It can be compared to client-server, three-tier web, and SOA. From a high-level perspective, much of application architecture is dedicated to determining where and how to execute logic and access data. For much of application architectural history, data access has driven the design of applications. Issues with access and consistency drive developers to design applications in such a way as to ensure optimal use of data stores and reliable consistency of that data across services. Business logic is distributed such that it is closest to that data, while the presentation layer is almost always distributed closest to the client.
Business logic can be contained in a single "application", such as in traditional architectures, or it can be distributed. This is the case with SOA and increasingly with microservices and serverless computing. This division of business logic is the driving design principle for microservices.
Microservices view an application as a collection of objects and functions that make up the "business logic". This logic enables us to 'checkout', 'track orders', 'manage profiles', and a hundred other application-specific tasks. The code that makes up 'checkout' and 'manage profile' can be grouped together neatly into a single microservice. Essentially, microservices architecture is a set of principles that, when applied to an application, determine how business logic is grouped and distributed across an 'application'.
Microservices architecture aims to group that logic as tightly as it can, and in the smallest sustainable chunks possible. This aligns well with agile methodologies that demand rapid, frequent iterations over the code. By isolating chunks of business logic, each chunk can be iterated over in isolation to allow new features and functionality to be delivered in a rapid fashion. The size of the microservice is largely determined by the development organization's ability to maintain the code and speed of delivery. Too many microservices introduces complexity that slows down delivery. Thus, most organizations have settled on fewer microservices and moved from a purely functional approach to a more object-oriented strategy.
Regardless, there are still more microservices that make up a modern application than there are in a traditional, three-tier web application.
The Impact on NetOps
So you might be thinking, so what? What does a NetOps care about how developers architect applications?
The impact on NetOps is largely operational. That is, instead of deploying one application, you must now find time to deploy and operate all the application services needed to support many more applications. This imposes a burden on every operational group in IT that makes up the deployment pipeline as it is likely that no two applications share the same deployment schedule.
This is true whether microservices are deployed in containers or not. Regardless of the deployment model - whether in individual VMs or in containers or even on bare-metal built servers - each microservice must be effectively treated as an individual application.
There are also technical and architectural impacts on NetOps, largely due to reliance on API paths rather hosts to route requests to the appropriate service. This can mean insertion of new app routing services in the network architecture to support potentially multiple layers of HTTP-based routing.
The simplicity or complexity of the routing environment is largely determined by how granular developers get during design and implementation. Highly granular, function-based microservices architectures can result in hundreds of tiny microservices. Less aggressive (and more reasonable in an enterprise setting) implementations will see smaller but still significant increases.
Getting familiar with microservices will be a boon to NetOps and a necessary step toward supporting the next generation of applications built on this application architecture evolution.