Microservices are small apps designed to fulfill a single purpose. Each microservice is principally in charge of a single “concern” within the larger system, perhaps surrounding a business line, and operates as a black box, communicating with the outside through REST APIs, event streaming, and message brokers. Microservices architecture commonly aims at breaking down larger applications into smaller services, each acting as their own service component to other microservices, or larger programs, giving information upon request, but also creating an interworking set of independent services.
An independent microservices approach to deployment affords organizations several capabilities over traditional monolithic approaches:
Conceptually, microservices are an idea born out of service-oriented architecture (SOA). But, technologically, microservices are an evolutionary step from SOA, thanks to the supporting technology of virtual machines, containers, and container orchestration software.
Microservices would not be as effective an approach if it weren’t for containers. Much like virtual machines, containers are a form of virtualization, but whereas VMs virtualize the hardware, allowing multiple operating systems to run concurrently on the same hardware, containers virtualize the OS, allowing multiple workloads to run on a single instance of an operating system.
Virtualization is the act of dividing up computational resources (CPU, RAM, storage, connectivity) and wrapping them into individual scopes. To these virtual spaces, they believe they are a real, full system, unaware they are just a part of a larger machine. This allows multiple environments to run on the same hardware, and is the fundamental makeup of the cloud space, allowing multiple users to access a cloud system that may be running many more environments than the physical infrastructure would seem to support.
Virtualization, using either VMs or containers, contributes to IT flexibility, agility, and scalability, however, containers are aptly suited for microservices. Compared to VMs, containers are much smaller because they virtualize at the user level. A container contains a package of software, with the necessary dependencies, including code, runtime, configuration, and system libraries for it to be able to run on a host. Container instances sit atop a container engine that orchestrates the creation of containers, their resource allocations, and manages them. In this way, a container can be created from an image, holding and running a microservice, giving it exactly the resources it needs, and finally can blink out of existence instantaneously when it’s no longer needed. Has the microservice failed to require it to be reset? Simply spin up a new container, and discard the failed one. Additional workloads press the system, responsive automatic scaling can duplicate containers to meet demand. Containers are light-weight and compared to VMs or a server reboot can multiply and collapse nearly instantly.
Monolithic architectures are a single-tiered application, including all the data access and user interface in one package for a single platform—think back to buying software in a box at a local store. For home users, this may seem manageable. For enterprise-level applications, these monoliths can be problematic to debug, update, and develop new releases, especially while maintaining the system- dependent business operations. Microservices architecture, on the other hand, is not a single application, but several small services working together, contributing to the whole user experience. A microservices approach and monolithic approach seem to be on opposite ends of a spectrum, but microservices are a response to the unwieldy mess that many monolith codebases have become.
Oftentimes, it is advised not to develop applications from the ground up starting only with microservices. It is better, to begin with, a central application codebase. While this at first seems like potential time savings—skipping the monolith altogether—by developing initial iterations into one application, teams actually save time, money, and management headaches because the code base is centralized and the inherited microservices dependency structure is not needed. In these beginning stages of development, this is simpler. Eventually, as services within the monolith demonstrate stability, they can be cleaved off into their own microservice, and removed from the monolith code.
Those microservices are now independent, capable of scaling as needed. Cleaving off the code which is most suited for scaling makes a good first microservice candidate. Individual teams can then be assigned to manage those microservices with dramatically less difficulty, and better efficiency.
Microservices running within containers is the preferred method. The ephemeral nature and size of containers match the size and flexibility needed for microservices. Managing containers is best performed through automation.
Docker and Kubernetes are the two most popular tools for containerizing microservices. Docker is concerned with creating containers, and Kubernetes is concerned with container orchestration, the automatic management of individual containers within clusters. Microservices and containers work so well together that they seem to be made for each other, however, microservices are not container dependent and can run in different environments. In each microservice scenario without containers, there are resource inefficiencies.
Primarily by making systems more resilient, flexible, and manageable, microservices architectures benefit developers, end-users, and the business goals of organizations. Below are some of the reasons companies are adopting microservice architectures.
With all the benefits and advantages that make microservices and containers attractive, it does come with its own set of challenges. Many on this list emerge from new complexities and ways of thinking about application development, by understanding and planning for them, many can be mitigated.
The core tools that enable microservices are in many ways common, but the convergence of these technologies delivers capabilities that many small, medium, and enterprise-size businesses cannot survive without today.
Managing and monitoring microservices requires the right tools. Teams can choose between forming a toolbox of apps that each help visualize an aspect of the whole system, such as using the information from a network monitoring app, a container monitoring app, and a log monitoring app to form a picture.
Another option is using an observability solution suite, which could be a single app or combination of products. These tools provide single-pane-of-glass visibility across the organization's infrastructure, applications, services, and cloud. These options must provide the following core capabilities:
Microservices are exceptional technologies when deployed within the cloud. Because cloud services are largely based on the virtualization technologies that enable VMs and containers, it provides a perfect and advantageous environment to deploy microservice architecture.