Microservices, Nanoservices, Teraservices, and Serverless

There is no question that monolithic applications can be developed using agile practices, and these are being developed all the time. Continuous integration (CI) and continuous deployment (CD) could be used, but the question is—do they use Agile practices effectively? Let's examine the following points:

Since monolithic applications are either bundled in the same archive or contained in a single directory, they prevent the deployment of code modularity. For example, many of you may have experienced the pain of delaying rolling out the whole release due to the failure of one feature.

To resolve these situations, microservices give us the flexibility to roll back only those features that have failed. It's a very flexible and productive approach. For example, let's assume you are the member of an online shopping portal development team and want to develop an application based on microservices. You can divide your application based on different domains such as products, payments, cart, and so on, and package all these components as separate packages. Once you have deployed all these packages separately, these would act as single components that can be developed, tested, and deployed independently, and called µService.

Now, let's see how that helps you. Let's say that after a production release launching new features, enhancements, and bug fixes, you find flaws in the payment service that need an immediate fix. Since the architecture you have used is based on microservices, you can roll back the payment service instead of rolling back the whole release, if your application architecture allows, or apply the fixes to the microservices payment service without affecting the other services. This not only allows you to handle failure properly, but it also helps to deliver the features/fixes swiftly to a customer.

To understand the microservices design, refer to the next diagram. As you can see, each component is autonomous. Each component could be developed, built, tested, and deployed independently. Here, even the application User Interface (UI) component could also be a client and consume the microservices. For the purpose of our example, the layer designed is used within the µService.

The API Gateway provides an interface where different clients can access the individual services and solve various problems, such as what to do when you want to send different responses to different clients for the same service. For example, a booking service could send different responses to a mobile client (minimal information) and a desktop client (detailed information), providing different details to each, before providing something different again to a third-party client.

A response may require the fetching of information from two or more services:

After observing all the sample design diagram we've just gone through, which is a very high-level design, you might find that in a monolithic design, the components are bundled together and tightly coupled. All the services are part of the same bundle. Similarly, you can see a variant where all services could have their own layers and form different APIs, but are also all bundled together.

Conversely, in a microservices design, the design components are not bundled together and have loose couplings. Each service has its own layers and database, and are bundled in a separate archive to all others. All these deployed services provide their specific APIs, such as Customers or Bookings. These APIs are ready to consume. Even the UI is also deployed separately and designed using µServices. For this reason, the microservices provide various advantages over their monolithic counterpart. Now let us discuss the limitations you'd face while working with monolithic applications.

One-Dimension Scalability

Monolithic applications that are large when scaled, scale everything, as all the components are bundled together. For example, in the case of a restaurant table reservation application, even if you would like to scale only the table-booking service, you would scale the whole application; you cannot scale the table-booking service separately. This design does not utilize resources optimally.

In addition, this scaling is one-dimensional. Running more copies of the application provides the scale with increasing transaction volume. An operation team could adjust the number of application copies that were using a load balancer based on the load in a server farm or a cloud. Each of these copies would access the same data source, therefore increasing the memory consumption, and the resulting I/O operations make caching less effective.

Microservices architectures give the flexibility to scale only those services where scale is required and allow optimal utilization of resources. As mentioned previously, when needed, you can scale just the table-booking service without affecting any of the other components. It also allows two-dimensional scaling; here we can not only increase the transaction volume, but also the data volume using caching (platform scale). A development team can then focus on the delivery and shipping of new features, instead of worrying about the scaling issues (product scale).

Microservices could help you scale platforms, people, and product dimensions, as we have seen previously. People scaling here refers to an increase or decrease in team size depending on the microservices' specific development needs.

Microservice development using RESTful web service development provides scalability in the sense that the server-end of REST is stateless; this means that there is not much communication between servers, which makes the design horizontally scalable.

Release Rollback in Case of Failure

Since monolithic applications are either bundled in the same archive or contained in a single directory, they prevent the deployment of code modularity. For example, many of you may have experienced the pain of delaying rolling out the whole release due to the failure of one feature.

To resolve these situations, microservices give us the flexibility to roll back only those features that have failed. It's a very flexible and productive approach. For example, let's assume you are the member of an online shopping portal development team and want to develop an application based on microservices. You can divide your application based on different domains such as products, payments, cart, and so on, and package all these components as separate packages. Once you have deployed all these packages separately, these would act as single components that can be developed, tested, and deployed independently, and called µService.

Now, let's see how that helps you. Let's say that after a production release launching new features, enhancements, and bug fixes, you find flaws in the payment service that need an immediate fix. Since the architecture you have used is based on microservices, you can roll back the payment service instead of rolling back the whole release, if your application architecture allows, or apply the fixes to the microservices payment service without affecting the other services. This not only allows you to handle failure properly, but it also helps to deliver the features/fixes swiftly to a customer.

Problems in Adopting New Technologies

Monolithic applications are mostly developed and enhanced based on the technologies primarily used during the initial development of a project or a product. This makes it very difficult to introduce new technology at a later stage of development or once the product is in a mature state (for example, after a few years). In addition, different modules in the same project that depend on different versions of the same library make this more challenging.

Technology is improving year over year. For example, your system might be designed in Java and then, a few years later, you may want to develop a new service in Ruby on Rails or Node.js because of a business need or to utilize the advantages of new technologies. It would be very difficult to utilize the new technology in an existing monolithic application.

It is not just about code-level integration, but also about testing and deployment. It is possible to adopt a new technology by rewriting the entire application, but it is a time-consuming and risky thing to do.

On the other hand, because of its component-based development and design, microservices architectures give us the flexibility to use any technology, new or old, for development. They do not restrict you to using specific technologies, and give you a new paradigm for your development and engineering activities. You can use Ruby on Rails, Node.js, or any other technology at any time.

So, how is this achieved? Well, it's very simple. Microservices-based application code does not bundle into a single archive and is not stored in a single directory. Each µService has its own archive and is deployed separately. A new service could be developed in an isolated environment and could be tested and deployed without any technical issues. As you know, microservices also own their own separate processes, serving their purpose without any conflicts to do with things such as shared resources with tight coupling, and processes remain independent.

Monolithic systems do not provide flexibility to introduce new technology. However, the introduction of new technology comes as low risk features in microservices-based systems, because, by default, these are small and self-contained components.

You can also make your microservice available as open source software so it can be used by others, and, if required, it may interoperate with a closed source, a proprietary one, which is not possible with monolithic applications.

Alignment With Agile Practices

There is no question that monolithic applications can be developed using Agile practices, and these are being developed all the time. Continuous integration (CI) and continuous deployment (CD) could be used, but the question is—do they use Agile practices effectively? Let's examine the following points:

• When there is a high probability of having stories dependent on each other, and there could be various scenarios, a story would not be taken up until the dependent story is complete.
• The build takes more time as the code size increases.
• The frequent deployment of a large monolithic application is a difficult task to achieve.
• You would have to redeploy the whole application even if you updated a single component.
• Redeployment may cause problems to already running components; for example, a job scheduler may change whether components impact it or not.
• The risk of redeployment may increase if a single changed component does not work properly or if it needs more fixes.
• UI developers always need more redeployment, which is quite risky and time-consuming for large monolithic applications.

The preceding issues can be tackled very easily by microservices. For example, UI developers may have their own UI component that can be developed, built, tested, and deployed separately. Similarly, other microservices might also be deployable independently and, because of their autonomous characteristics, the risk of system failure is reduced. Another advantage for development purposes is that UI developers can make use of JSON objects and mock Ajax calls to develop the UI, which can be taken up in an isolated manner. After development is finished, developers can consume the actual APIs and test the functionality. To summarize, you could say that microservices development is swift and it aligns well with the incremental needs of businesses.

Ease of Development – Could Be Done Better

Generally, large monolithic application code is the toughest to understand for developers, and it takes time before a new developer can become productive. Even loading the large monolithic application into an integrated development environment (IDE) is troublesome, as it makes the IDE slower and the developer less productive.

A change in a large monolithic application is difficult to implement and takes more time due to the large code base, and there can also be a high risk of bugs if impact analysis is not done properly and thoroughly. Therefore, it becomes a prerequisite for developers to do a thorough impact analysis before implementing any changes.

In monolithic applications, dependencies build up over time as all components are bundled together. Therefore, the risk associated with code changes rises exponentially as the amount of modified lines of code grows.

When a code base is huge and more than 100 developers are working on it, it becomes very difficult to build products and implement new features because of the previously mentioned reason. You need to make sure that everything is in place, and that everything is coordinated. A well-designed and documented API helps a lot in such cases.

Netflix, the on-demand internet streaming provider, had problems getting their application developed, with around 100 people working on it. Then, they used a cloud service and broke up the application into separate pieces. These ended up being microservices. Microservices grew from the desire for speed and agility and to deploy teams independently.

Microcomponents are made loosely coupled thanks to their exposed APIs, which can be continuously integration tested. With microservices' continuous release cycle, changes are small and developers can rapidly exploit them with a regression test, then go over them and fix the defects found, reducing the risk of a flawed deployment. This results in higher velocity with a lower associated risk.

Owing to the separation of functionality and the single responsibility principle, microservices make teams very productive. You can find a number of examples online where large projects have been developed with very low team sizes, such as 8 to 10 developers.

Developers can have better focus with smaller code bases and better feature implementation, leading to a higher empathetic relationship with the users of the product. This proves conducive to better motivation and clarity in feature implementation. An empathetic relationship with users allows for a shorter feedback loop and better and speedier prioritization of the feature pipeline. A shorter feedback loop also makes defect detection faster.

Each microservices team works independently and new features or ideas can be implemented without being coordinated with larger audiences. The implementation of endpoint failure handling is also easily achieved in the microservices design.

At a recent conference, a team demonstrated how they had developed a microservices-based transport-tracking application for iOS and Android, within 10 weeks, with Uber-type tracking features. A big consulting firm gave a seven-month estimation for this application to its client. This shows how microservices design is aligned with Agile methodologies and CI/CD.

So far, we have discussed only the microservices design—there are also nanoservices, teraservices, and serverless designs to explore.

Nanoservices

Microservices that are especially small or fine-grained are called nanoservices. A nanoservices pattern is really an anti-pattern.

In the case of nanoservices, overheads such as communication and maintenance activities outweigh its utility. Nanoservices should be avoided. An example of a nanoservices (anti-) pattern would be creating a separate service for each database table and exposing its CRUD operation using events or a REST API.

Teraservices

Teraservices are the opposite of microservices. The teraservices design entails a sort of a monolithic service. Teraservices require two terabytes of memory, or more. These services could be used when services are required only to be in memory and have high usage.

These services are quite costly in cloud environments due to the memory needed, but the extra cost can be offset by changing from quad-core servers to dual-core servers.

Such a design is not popular.

Serverless

Serverless is another popular cloud architecture offered by cloud platforms such as AWS. There are servers, but they are managed and controlled by cloud platforms.

This architecture enables developers to simply focus on code and implementing functionality. Developers need not worry about scale or resources (for instance, OS distributions as with Linux, or message brokers such as RabbitMQ ) as they would with coded services.

A serverless architecture offers development teams the following features: zero administration, auto-scaling, pay-per-use schemes, and increased velocity. Because of these features, development teams just need to care about implementing functionality rather than the server and infrastructure.

If you enjoyed reading this article, head to packtpub.com to get more indepth understanding and insights into the world of Microservices.