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What is serverless?
Let’s examine serverless and Functions-as-a-Service (FaaS), how they fit together, and where they do and don’t make sense
You likely have heard the term serverless (and wondered why someone thought it didn’t use servers). You may have heard of Functions-as-a-Service (FaaS) – perhaps in the context of Lambda from Amazon Web Services, introduced in 2014. You’ve probably encountered event-driven programming in some form. How do all these things fit together and, more importantly, when might you consider using them? Read on.
Let’s start with FaaS. With FaaS, you write code to accomplish some specific task and upload the code for our function to a FaaS provider. The public cloud provider or on-premise platform then does everything else necessary to provision, run, scale, and manage the code. As a developer, you don’t need to do anything other than write your code and wire it up to other functions and services. FaaS provides programmers with an abstraction that allows them to focus on just writing code that takes action in response to events rather than interacting with the underlying server (whether bare metal, virtualized, or containerized).
[ Struggling to explain containers to non-techies? Read also: How to explain containers in plain English. ]
Now enter event-driven programming. Functions run in response to external events. It could be a call generated by a mouse click in a web app. But it could also be in response to some other action. For example, uploading a media file could trigger custom code that transcodes the file into a variety of formats.
Serverless then describes a set of architectural patterns that build on FaaS. Serverless combines custom FaaS code with common back-end services (such as databases and authentication) connected primarily through an event-driven execution model. From the perspective of a developer, these services are all managed by a third-party (whether an ops team or an external provider). Of course, servers are still involved; developers just don’t need to think about them in a traditional way.
Serverless is an emerging technology area. There’s a lot of interest in the technology and approach although it’s early on and has yet to appear on many enterprise IT radar screens. To understand the interest, it’s useful to consider serverless from both operations and developer perspectives.
For operations teams, one of the initial selling points of FaaS on public clouds was its pricing model. By paying only for an ephemeral (typically stateless) function while it was executing, you “didn’t pay for idle.” In general, while this aspect of serverless is still important to some, it’s less emphasized today. As a broader concept that brings in a wide range of services of which FaaS is just one part, the FaaS pricing model by itself is less relevant.
However, pricing model aside, serverless also allows operations teams to provide developers with a self-service platform and then get out of the way. This is a concept that has been present in platforms like OpenShift from the beginning. Serverless effectively extends the approach for certain types of applications.
The arguably more important aspect of serverless is increased developer productivity. This has two different aspects.
The first is that, as noted earlier, FaaS abstracts away many of the housekeeping details associated with server provisioning and management that are often just overhead for developers. In practice, this may not appear all that different to developers than a Platform-as-a-Service (PaaS). FaaS can even use containers under the covers just like a PaaS typically does. PaaS and FaaS are best thought of as being on a continuum rather than being entirely discrete.
The second is that, by offering common managed services out of the box, developers don’t need to constantly recreate them for new applications.
Where does serverless fit?
Serverless targets specific architectural patterns. As described earlier, it’s more or less wedded to a programming model in which functions and services react to each other in an event-driven and largely asynchronous way. Functions themselves are generally expected to be stateless, handle single tasks, and finish quickly. The fact that the interactions between services and functions are all happening over the network also means that the application as a whole should be fairly tolerant of latencies in these interactions.
While there are overlaps between the technologies used by FaaS, microservices, and even coarser-grained architectural patterns, you can think of FaaS as both simplifying and limiting. FaaS requires you to be more prescriptive about how you write applications.
Although serverless was originally most associated with public cloud providers, that comes with a caveat. Serverless, as implemented on public clouds, has a high degree of lock-in to a specific cloud vendor. This is true to some degree even with FaaS, but serverless explicitly encourages bringing in a variety of cloud provider services that are incompatible to varying degrees with other providers and on-premise solutions.
As a result, there’s considerable interest in and work going into open source implementations of FaaS and serverless, such as Knative and OpenWhisk, so that users can write applications that are portable across different platforms.
[ What's next for portable apps? Read also: Disrupt or be disrupted: 3 trends enabling next-level IT agility. ]
The speedy road ahead
Building more modern applications is a top priority for IT executives as part of their digital transformation journeys; it’s seen as the key ingredient to moving faster. To that end, organizations across a broad swath of industries are seeking ways to create new applications more quickly. Doing so involves both making traditional developers more productive and seeking ways to lower the barriers to software development for a larger pool of employees.
Serverless is an important emerging service implementation architecture that will be a good fit for certain types of applications. It will coexist with, rather than replace, architecture alternatives such as microservices used with containers and even just virtual machines. All of these architectural choices support a general trend toward simplifying the developer experience and making developers more productive.
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