Serverless vs Containers: Differences and Which one to Choose?

Jan 10, 2022 | Software Development | 0 comments

It’s 2022 and like most of the ongoing trends of DevOps, going serverless or using containers for application deployment seem to be a common point of debate in the tech community. And we still feel it’s not going to end anytime soon in software development. However, Is the Serverless vs Containers comparison popular just because some cloud enthusiasts feel that serverless computing is a replacement for containers? OR Is it because some people feel that serverless is just another technology that can be used inside containers?

Let’s have a feature by feature comparison of Serverless vs Containers so as to get a proper idea about each deployment option and try to find out which one to use when:

Longevity Limitations

Serverless: As you may know, functions live very ‘short’. Here, short can be defined as 5 minutes or less. Functions are ephemeral, means, the container running the function may live for only once and die after its execution.

Shorter lifespan is one of the caveats of functions but it also provides agility which gives developers freedom and flexibility to push apps into the production which are easy to scale.

Containers: This is not the case with containers. Containers are always running and spinning and they do not die once their execution is done. This empowers them to leverage the benefit of caching, about which we will discuss later, but at the same time, scaling is not instantaneous.

State Persistency

Serverless: As discussed in the above point, functions are ephemeral or ‘short-lived’ which in turn, makes them stateless. The more stateless your functions are, the more ways there are to put them together and build something powerful.

The power of stateless computing lies in the ability to empower developers to write powerful, reusable functions and combine them. But it comes with the downside of caching. Since functions are stateless, you cannot cache anything for the further use, as a result, it faces high latency about which we will discuss in next point.

Containers: With containers, you can leverage the benefits of caching. To allow the data to be stored even when the containers are terminated, you’ll need to use a storage mechanism that will manage the data outside of the container. Anyways, why caching is so important?

If the objects on the object file that container is about to produce is same as the previous builds, reusing a cache from the previous result is a great time saver in terms of computing. This enables the building of new containers extremely fast.

Latency & Start-up Time

Serverless: Since functions are stateless, caching is unavailable and they don’t have copies of your functions running on standby, it results in higher invocation time. Functions stay warm, or your code is running while getting a command to be executed, for 15 minutes and die, hence, if you call it after the specified time, it will be a cold start.

As a result, you may face latency issues especially when there are concurrent users. To tackle this, you will need to add a code.

However, this is temporary and can be used while you’re dealing with fewer functions. If you’re using it for all the functions, soon there will be a lot of dummy functions and then you won’t be able to manage it properly. However, the number of the function is quite small, it makes sense to use functions rather than spinning a whole container.

Containers: Considering the pre-serverless era of containers, these are always sitting there and all you have to do is send an HTTPS request to it and you get an instant response and low latency time. With caching at the advantage, containers can be spun fast with none of the files to be created again, as a reference to them is sufficient to locate and reuse the already built structures.

Scalability

Serverless: In serverless architecture, the backend of an application automatically and inherently scales to meet demand of the desired scalability. Moreover, Serverless Computing can be compared to the functioning manner of a water supply: your supply provider turn the tap on and your consumers can acquire as much water they need at any time. They only pay for what they use. This concept is far more scalable than the attempt to buy water one bucket, or shipping one container at a time.

Containers: While using a container-based architecture, it’s the job of a developer to determine the number of containers to be deployed in advance when it comes to scale the application according to the desired needs. Moreover, with the increased demand a shipping company would try to ship more containers to the destination to meet that demand. But this won’t be much scalable either when demand of consumers exceeds the shipping company’s expectation.

Portability & Migration

Serverless: Let’s assume you’re already using many different services of AWS. If this is the case, then opting for Lambda functions would be extremely easy as it facilitates fast and accessible integration with its other services.

Even if it’s not the case and you fear vendor lock-in, what you can do is to make sure all API endpoints and URLs used in your code get mapped through a domain/change via DNS is under your control.

This gives you an option of cutting off a particular service or redirecting them to a different endpoint of your choice (e.g. another BaaS provider). This is better than hard coding your code in an endpoint which is not under your control or is unalterable.

However, there are many FaaS providers and your concern for vendor lock-in is quite obvious. In case of Lambda, if it isn’t meeting your region specific requirements, here is what you can do. All Lambda handler code should be isolated and extremely thin shims to logic that is locked up in other modules/classes.

This increases reusability and in the event that a refactor is necessary to move out of Lambda, makes that work much easier and straightforward. This also facilitates unit testing.

Speaking of migration, it is still hazy how to fit FaaS into the current DevOps framework. It might happen that your organisation will write hundreds of function and after a time, nobody knows what functionalities were included in which functions and how many of them are still in use.

Containers: If you’re opting for container-based microservices architecture, these provide great portability. The time and efforts to move the code from developer’s laptop to your internal datacenter or out to different cloud providers are minimal.

With the immense stress on innovation and time to market are getting lesser and lesser, opting for microservices empowers you to spin up new versions of your application.

Hence microservices sounds like a good option to get started if you’re moving from monoliths due to ease in migration and various option for technology stack for multiple containers.

However, running a container on a cloud platform has a huge amount of interdependencies. Such as upgrades need to be planned together which includes container hosts, container images, container engine and container orchestration.

For some legacy applications that you want to shift to microservices, ‘containerizing’ them might be an easy and cheap option than to re-architecting the whole application into functions.

Development Environments & Language Support

Serverless: The language supported by popular FaaS providers are quite limited which mainly includes Node.js, Python, Java, C# and Go (in case of AWS Lambda).

Containers: While containers empowers you with heterogeneous development environments and you can work on any technology stack you want. It might not sound like a huge benefit since developers these days are well-versed with multiple languages, but it is!

When you’ll be hiring for your new project, you won’t be required to take language into considerations for microservice architecture. Since microservices are independently deployable and scalable with each service providing a firm module boundary, services can be written in the language of any choice and can be managed by different teams.

System Control

Serverless: Dealing with functions such as AWS Lambda doesn’t come off as a hard task as it eliminates the infrastructure complexity, as a result, you can focus more on developing your product and business outcomes. It significantly reduces the time to market which is not the case with containers. However, there is a long list of things that should not be done while using AWS Lambda.

Containers: Plus, management of cluster configuration is a serious challenge as it prerequisites solid background in container technology. Talking about the control, microservices are comparatively easy to handle. 

Container-based microservice architecture imparts you full control over the individual as well as the whole system. This enables you to set policies, allocate and manage resources. Plus, having fine grain control over the security and migration services.

With the full control over the container system comes the ability to see inside and outside of the containers. This allows comprehensive and effective testing & debugging using multiple environments and extensive resources. Whereas actual implementation and local testing of functions aren’t possible and hence it is hard to guess the performance issues.

Resource Heavy Processing

Let’s take an example of AWS Lambda, if the function is taking more than 5 minutes, you’ll be mandated to dissect these tasks into smaller ones, plus, these are not the only limitations while working with them.

You can allocate the maximum of 1.5 GB of RAM for executing a single function, your deployment package should not exceed the maximum size of 50 MB. Whereas with containers, you can allocate the computing resources as per your application requirements.

Testing

Serverless: Testing is difficult in serverless based web applications as it often becomes hard for developers to replicate the backend environment on a local environment.

Containers: Since containers run on the same platform where they are deployed, it’s relatively simple to test a container-based application before deploying it to the production.

Maintenance

Serverless: Maintenance in Serverless based applications is much easier than you can ever imagine. Since your serverless vendor such as AWS lambda takes care of all sort of things such as management and software updates to the server, overall maintenance is less.

Containers: Unlike Serverless – with which a developer don’t have to think about maintenance – it’s a developer job to manage and update each container he deploy.

Cost

Serverless: As already mentioned above, using Serverless functions such as AWS lambda for application deployment prevents you for bearing unnecessary expenses of resources because application code does not run unless it is called. Instead, you will be charged for the server capacity that your application is going to use, anyways. If you want to have a clear overview regarding AWS lambda pricing, we’ve already covered that in our previous blog post.

Containers: Containers are constantly running, and therefore cloud providers have to charge for the server space even if no one is using the application at the time.

Time of Deployment

Serverless:  Since serverless functions are smaller than container microservices and they do not come bundled with system dependencies, it takes only milliseconds to deploy an application. Moreover, Serverless applications goes live as soon as the code is deployed.

Containers: Although, Containers take longer to setup at the initial stages of development but once configured they only take few seconds to deploy.

When to choose what?

Now it’s time for the big question:

“Which technology should I pick for my next project”? Truthfully, it depends.

Overall, containers are better if you want complete control over your application environment. Containers are particularly useful when migrating monolithic legacy applications to the cloud because you can easily replicate the application’s running environment.

When to Use Containers? : Containers Use Case

Containers are best to use for Application deployment in following use cases:

  • If you want to use the operating system of your own choice and leverage full control over the installed programming language and runtime version.
  • If you want to use software with specific version requirements, containers are great to start with.
  • If you are okay in bearing cost of using big yet traditional servers for anything such as Web APIs, machine learning computations, and long-running processes, then you might also want to try out containers as well (They will cost you less than servers anyways)
  • If you want to develop new container-native applications
  • If you need to refactor a very large and complicated monolithic application, then it’s better to use container as it’s better for complex applications
  • Container orchestration platforms such as Docker can solve your issues with unpredictable traffic (auto-scaling), however, the process of spinning containers up or down won’t be instantaneous.

Serverless architecture works well for teams that want to write and release applications quickly without the responsibility of managing and maintaining servers or underlying infrastructure. You should also consider serverless functions if you have unpredictable workloads that will be difficult to smoothly scale up or down in a container-based system.

When to Use Serverless? : Serverless Use Cases

Serverless Computing is perfect fit for the following use-cases:

  • If your traffic pattern changes automatically. Not only it will be handled automatically, it will even shut down when there is no traffic at all.
  • If you are worried about the cost of maintenance of servers and the resources your application consume, serverless will be great fit for such use-case
  • If you don’t want to spend much time in thinking where your code is running and how!
  • Serverless websites and applications can be written and deployed without handling the work of setting up infrastructure. As such, it is possible to launch a fully-functional app or website in days using serverless.
  • Serverless architecture allows you to build performance-enhancing image and video services for any application. You can use its services to do things like dynamically resize images or change video transcoding for different target devices.

That said, another option is to create a hybrid architecture where some functions are deployed in containers and some run on serverless, so it doesn’t have to be one or the other. What’s important is that your applications run in the most suitable environment for their respective use cases.

Conclusion

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