第12章クラウドネイティブアプリケーション開発

Learn more about use cases for using a serverless architecture (https://openstax.org/r/76usecasesserv) in three specific application areas.

PaaS provides a platform that allows customers to provision and scale the infrastructure needed as well as develop, run, and manage applications without the complexity of managing the underlying infrastructure required to run the application. FaaS goes a step further in that it provides an environment where developers can focus on running and managing code without having to provision resources or scaling the underlying infrastructure. In summary, both FaaS and PaaS provide an infrastructure managed by the cloud service provider. Both provide scalability options. Both deliver high availability from remote infrastructure managed automatically by the cloud service provider at scale. FaaS/serverless and PaaS, on the surface, appear to be very similar in their implementation and use from a development point of view. In reality, these two cloud deployment services are quite different. Scalability, pricing, start-up time, tooling, and the ability to deploy differ between the two platforms.

Serverless applications offer true auto-scaling capabilities to customers without any additional configurations. PaaS provides scalability options that are more advantageous compared to deployments on bare metal servers. However, developers still must consider how to construct and scale a PaaS platform. They must forecast resource capacity and configure PaaS-hosted applications to scale up and down based on demand. Serverless cost structure is based on usage, and there are no fixed monthly charges for services. With FaaS, customers pay per event-based invocation of the function only. With PaaS, pricing models differ depending on the PaaS provider, and are generally associated with the use of compute, storage, and network resources costs. This means, for PaaS, costs accrue during idle time. In some cases, serverless can be a more cost-effective option for software deployments.

FaaS functions execute in response to events, offering rapid start-up times crucial for event-based processing. Conversely, PaaS applications lack event-triggered start-up capabilities and are tolerant of slower start-up times due to their long-lived nature. FaaS abstracts the application layer, allowing developers to focus solely on function code while cloud service providers manage other aspects. This abstraction, however, reduces flexibility, as developers must adhere to provider-specific frameworks and language limitations. PaaS, on the other hand, offers developers greater control over the development environment, including the choice of programming languages and frameworks.

There are at least three application areas where it makes sense to go serverless:

1. Unpredictably fluctuating workloads or frequent low usage ideal for the pricing model of FaaS/ serverless solutions.

2. Processing large, distributed data sources because of the feasibility of auto-scaling of FaaS/serverless environments where computing performance can be dramatically boosted.

3. Building highly modular solutions potentially incorporating external services that can also exploit the pricing model of FaaS/serverless solutions.

More generally, serverless architecture is ideal for asynchronous, stateless applications that can be started instantaneously. Likewise, serverless is a good fit for use cases that see infrequent, unpredictable surges in demand, that are high-volume, and with parallel workloads. An example of an infrequent in-demand task would be a batch processing of incoming image files. This task can be high-volume if a large batch of images to be processed arrives all at once. Serverless is also a good fit for use cases that involve incoming data stream processing for implementing applications such as chat bots, scheduled tasks, or business logic. Some other common serverless use cases are back-end APIs and web apps, business process automation, serverless websites, and integration across multiple systems.

CSPs offer several serverless services. Understanding the minute differences between these services can be overwhelming, making it challenging to select the set of services to develop an optimal serverless architecture. It is expected to invest up-front time to get familiar with these services to understand the runtime expectations and resource consumption associated with a prospective serverless solution. It is also challenging to maintain a serverless architecture in a continuous deployment procedure.

There are many cloud deployment technology options available to customers, which will continue to evolve. The vast possibilities available provide support for a wide host of services. The sections that follow provide insight into common use cases that are associated with the use of these deployment technology options.