To get a concept of containerization in app development, we need to have a look at the role of containers in shipping.
Before containers were invented by Malcolm McLean in 1956, everything that needed to be transported was individually loaded on a ship. This took a lot of time and effort. The loading and unloading effort used to take more time than the actual shipping.
Containers made it modular. No matter what is in the container, just lift it up and place it in the ship.
The same is the case with application containerization.
What is Application Containerization?
Containerization, in the terms of software development, is an OS-level virtualization method that is used to run and deploy applications distributed across hosts without launching an entire virtual machine for an app.
Multiple isolated application services (containers) can be run on a single host via the same OS kernel.
Containers can be used on the cloud, on virtual machines, across Linux, and on some Windows and Mac operating systems.
Let’s have a closer look at how application containerization works.
How does Containerization work?
Application containers contain everything needed by an application to function. This includes the files, environment variables, and libraries.
Containers need fewer resources to run as compared to a similar deployment on a virtual machine. This is because containers can share resources and hence do not need the full OS to support the application.
The complete set of information needed to run an app via a container is called an image. The container engine deploys these images on the hosting machine (physical or virtual) to run the app.
Application containerization works based on microservices and distributed applications. Each container deploys independently of the others and hence uses minimum resources from the host. Application programming interfaces (APIs) let the microservices communicate amongst themselves.
When the demand for an application component rises, the container virtualization layer scales up the microservices to meet the demand.
Virtualization makes it possible for developers to present an amount of physical computational resources as a virtual machine. This limits the maximum strain a containerized app can put on the host.
This greatly enhances flexibility. If the demand for an application component rises, the developer can adjust the resources allocated to a container without making drastic changes to the app or the host.
Updating applications is also easier with containerization. All a developer has to do is to make changes to the container image. The image can then be redeployed on the host to make the update available. This makes it possible to deliver updates seamlessly without having to take the app down.
But why do we need to use containers? What are the advantages of this approach? And what are some of the drawbacks/compromises?
Advantages of Containerization
Containerization is an application development approach that is centered around efficiency and portability. The main benefits of using this approach include:
One of the main benefits of containerization is the efficient use of computational resources like CPU, memory, and storage. Containerized apps tend to be more resource-efficient than traditionally virtualized or physically hosted apps.
As there is no need for overheads for virtual machines, more containerized apps can be run using the same hardware/virtual resources.
Another benefit of containerization is portability. As long as two systems are running the same OS, a container can very easily be transplanted across systems without needing any changes in the code. As a container is totally self-sufficient, it has no dependency on guest OS environment variables or libraries.
All the development is saved as an image and that image can be copied and used anywhere. That eliminates the need for system con.
One of the main benefits of implementing application containerization is reproducibility. This is, in fact, one of the main reasons container adoption has become an important part of the DevOps methodology.
When using this approach, the file systems, binaries, and all other information stay the same throughout the application development lifecycle, from code building to deployment.
Container security as part of Containerzation
Container security (when applied) also makes apps safer. If there’s an intrusion into a container at any level, it will be contained there and will not spread anywhere in the app or the host machine.
However, containerization, like anything else in the world, is not the perfect approach. It has its own drawbacks. Here are some of them:
Drawbacks of Containerization
Lack of Isolation
One of the chief compromises that you have to make while using a containerized approach is that containers are not isolated from the core OS of the machine they are running on.
Some experts argue that containers have a higher access level and an infected container can compromise the security of the host.
However, if the policies dictating the access are clearly defined and security risks are mitigated according to the industry standards, this thing can be eliminated.
This tech is still new
Application containerization is a relatively new and very rapidly growing enterprise-level IT methodology. Resultantly, the whole thing is under constant change and instability is inevitable.
In addition, there is still a general lack of information and expertise about this field which makes it difficult to implement it on an enterprise level.
Containers are specific to the OS they are created for. If an enterprise wants to run a container from Windows on a Linux System or vice versa, they’ll need to add a compatibility layer or use nested virtual machines. This can work as a make-shift solution but greatly increases resource consumption.
To sum it up, containerization is an application development methodology that is formulated to make applications smart. Containerized apps only utilize the minimum possible amount of resources at any given time and hence more apps can be run using comparable hardware/virtual resources.
However, containers come with their own drawbacks like a lack of isolation from the host OS and a relatively complicated process for transplanting them across OSes.