We are in the middle of a series of blogs on Software Defined Datacenters (SDDC) @ http://www.vamsitalkstech.com/?p=1833. The key business imperative driving the SDDC architectures is their ability to natively support digital applications. Digital applications are “Cloud Native” (CN) in the sense that these platforms are originally being written for cloud frameworks – instead of being ported over to the Cloud as an afterthought. Thus, Cloud Native application development emerging as the most important trend in digital platforms. This blog post will define the seven key architectural characteristics of these CN applications.
What is driving the need for Cloud Native Architectures…
The previous post in the blog covered the monolithic architecture pattern. Monolithic architectures , which currently dominate the enterprise landscape, are coming under tremendous pressures in various ways and are increasingly being perceived to be brittle. Chief among these forces include – massive user volumes, DevOps style development processes, the need to open up business functionality locked within applications to partners and the heavy human requirement to deploy & manage monolithic architectures etc. Monolithic architectures also introduce technical debt into the datacenter – which makes it very difficult for the business lines to introduce changes as customer demands change – which is a key antipattern for digital deployments.
Applications that require a high release velocity presenting many complex moving parts, which are worked on by few or many development teams are an ideal fit for the CN pattern.
Introducing Cloud Native Applications…
There is no single and universally accepted definition of a Cloud Native application. I would like to define a CN Application as “an application built using a combination of technology paradigms that are native to cloud computing – including distributed software development, a need to adopt DevOps practices, microservices architectures based on containers, API based integration between the layers of the application, software automation from infrastructure to code, and finally orchestration & management of the overall application infrastructure.”
Further, Cloud Native applications need to be architected, designed, developed, packaged, delivered and managed based on a deep understanding of the frameworks of cloud computing (IaaS and PaaS).
Characteristic #1 CN Applications dynamically adapt to & support massive scale…
The first & foremost characteristic of a CN Architecture is the ability to dynamically support massive numbers of users, large development organizations & highly distributed operations teams. This requirement is even more critical when one considers that cloud computing is inherently multi-tenant in nature.
Within this area, the typical concerns need to be accommodated –
- the ability to grow the deployment footprint dynamically (Scale-up) as well as to decrease the footprint (Scale-down)
- the ability to gracefully handle failures across tiers that can disrupt application availability
- the ability to accommodate large development teams by ensuring that components themselves provide loose coupling
- the ability to work with virtually any kind of infrastructure (compute, storage and network) implementation
Characteristic #2 CN applications need to support a range of devices and user interfaces…
The User Experience (UX) is the most important part of a human facing application. This is particularly true of Digital applications which are omnichannel in nature. End users could not care less about the backend engineering of these applications as they are focused on an engaging user experience.
Accordingly, CN applications need to natively support mobile applications. This includes the ability to support a range of mobile backend capabilities – ranging from authentication & authorization services for mobile devices, location services, customer identification, push notifications, cloud messaging, toolkits for iOS and Android development etc.
Characteristic #3 They are automated to the fullest extent they can be…
The CN application needs to be abstracted completely from the underlying infrastructure stack. This is key as development teams can focus on solely writing their software and does not need to worry about the maintenance of the underlying OS/Storage/Network. One of the key challenges with monolithic platforms (http://www.vamsitalkstech.com/?p=5617) is their inability to efficiently leverage the underlying infrastructure as they have a high degree of dependency to it. Further, the lifecycle of infrastructure provisioning, configuration, deployment, and scaling is mostly manual with lots of scripts and pockets of configuration management.
The CN application, on the other hand, has to be very light on manual asks given its scale. The provision-deploy-scale cycle is highly automated with the application automatically scaling to meet demand and resource constraints and seamlessly recovering from failures. We discussed Kubernetes in one of the previous blogs.
Frameworks like these support CN Applications in providing resiliency, fault tolerance and in generally supporting very low downtime.
Characteristic #4 They support Continuous Integration and Continuous Delivery…
The reduction of the vast amount of manual effort witnessed in monolithic applications is not just confined to their deployment as far as CN applications are concerned. From a CN development standpoint, the ability to quickly test and perform quality control on daily software updates is an important aspect. CN applications automate the application development and deployment processes using the paradigms of CI/CD (Continuous Integration and Continuous Delivery).
The goal of CI is that every time source code is added or modified, the build process kicks off & the tests are conducted instantly. This helps catch errors faster and improve quality of the application. Once the CI process is done, the CD process builds the application into an artifact suitable for deployment after combining it with suitable configuration. It then deploys it onto the execution environment with the appropriate identifiers for versioning in a manner that support rollback. CD ensures that the tested artifacts are instantly deployed with acceptance testing.
Characteristic #5 They support multiple datastore paradigms…
The RDBMS has been a fixture of the monolithic application architecture. CN applications, however, need to work with data formats of the loosely structured kind as well as the regularly structured data. This implies the need to support data streams that are not just high speed but also are better suited to NoSQL/Hadoop storage. These systems provide Schema on Read (SOR) which is an innovative data handling technique. In this model, a format or schema is applied to data as it is accessed from a storage location as opposed to doing the same while it is ingested. As we will see later in the blog, individual microservices can have their own local data storage.
Characteristic #6 They support APIs as a key feature…
APIs have become the de facto model that provide developers and administrators with the ability to assemble Digital applications such as microservices using complicated componentry. Thus, there is a strong case to be made for adopting an API centric strategy when developing CN applications. CN applications use APIs in multiple ways – firstly as the way to interface loosely coupled microservices (which abstract out the internals of the underlying application components). Secondly, developers use well-defined APIs to interact with the overall cloud infrastructure services.Finally, APIs enable the provisioning, deployment, and management of platform services.
Characteristic #7 Software Architecture based on microservices…
As James Lewis and Martin Fowler define it – “..the microservice architectural style is an approach to developing a single application as a suite of small services, each running in its own process and communicating with lightweight mechanisms, often an HTTP resource API. These services are built around business capabilities and independently deployable by fully automated deployment machinery. There is a bare minimum of centralized management of these services, which may be written in different programming languages and use different data storage technologies.” 
Microservices are a natural evolution of the Service Oriented Architecture (SOA) architecture. The application is decomposed into loosely coupled business functions and mapped to microservices. Each microservice is built for a specific granular business function and can be worked on by an independent developer or team. As such it is a separate code artifact and is thus loosely coupled not just from a communication standpoint (typically communication using a RESTful API with data being passed around using a JSON/XML representation) but also from a build, deployment, upgrade and maintenance process perspective. Each microservice can optionally have its localized datastore. An important advantage of adopting this approach is that each microservice can be created using a separate technology stack from the other parts of the application. Docker containers are the right choice to run these microservices on. Microservices confer a range of advantages ranging from easier build, independent deployment and scaling.
A Note on Security…
It goes without saying that security is a critical part of CN applications and needs to be considered and designed for as a cross-cutting concern from the inception. Security concerns impact the design & lifecycle of CN applications ranging from deployment to updates to image portability across environments. A range of technology choices is available to cover various areas such as Application level security using Role-Based Access Control, Multifactor Authentication (MFA), A&A (Authentication & Authorization) using protocols such as OAuth, OpenID, SSO etc. The topic of Container Security is very fundamental one to this topic and there are many vendors working on ensuring that once the application is built as part of a CI/CD process as described above, they are packaged into labeled (and signed) containers which can be made part of a verified and trusted registry. This ensures that container image provenance is well understood as well as protecting any users who download the containers for use across their environments.
In this post, we have tried to look at some architecture drivers for Cloud-Native applications. It is a given that organizations moving from monolithic applications will need to take nimble , small steps to realize the ultimate vision of business agility and technology autonomy. The next post, however, will look at some of the critical foundational investments enterprises will have to make before choosing the Cloud Native route as a viable choice for their applications.
 Martin Fowler – https://martinfowler.com/intro.html