Containerized Applications: Components, Use Cases, and Best Practices

What Are Containerized Applications? 

Containerized applications are software and services encapsulated in containers. Each container includes the application and its dependencies, libraries, and other binaries required to run the application isolated from the host system. This method ensures consistency across development, testing, and production environments.

Containers are executed by container engines, such as Docker or Kubernetes, allowing multiple containers to run on a single machine without interfering with each other. This architecture simplifies deployment and scaling by abstracting away the underlying infrastructure.

This is part of a series of articles about Docker container.

In this article:

• Containerized Application Adoption Trends
• Benefits of Containerization
• How Containerized Applications Work: 5 Components of a Containerized Environment
• Containerized Applications Use Cases
• The Challenges of Containerized Applications
• Best Practices for Managing Containerized Applications 

Containerized Application Adoption Trends 

According to Gartner’s new Container Management Magic Quadrant report, the container management market is experiencing rapid growth, with a market value of $1.6 billion in 2022, expected to reach over $3.6 billion by 2027. There is also increasing adoption of the public cloud, with the percentage of containers adopted in within public cloud environments expected to grow from 50% in 2023 to 75% in 2026.

At the same time, a Red Hat survey shows that container security concerns are on the rise. 67% of organizations surveyed reported they delayed or slowed down container deployments due to security issues. 84% of organizations reported they have an active DevSecOps initiative and are working to improve collaboration of development, security, and operations in container operations. More than 50% of respondents were concerned about container vulnerabilities and misconfigurations.

Related content: Read our guide to what is a container

Benefits of Containerization

Containers offer the following advantages for application development and management:

Isolation

With containers, each containerized application runs in its separate environment. This prevents conflicts between applications or versions of software, and simplifies dependency management, because each application has its own set of libraries.

Portability

Containers can run on any system that has a container engine. This makes applications platform-independent and ensures they run the same way on a developer’s laptop, in a test environment, or in the cloud. This flexibility enables teams to use a wide range of environments and cloud providers without modifying applications. 

Lightweight

Containers are lightweight because they share the host system’s kernel and do not need the overhead of an entire operating system. This results in faster startup times and less consumption of resources compared to virtual machines.

Scalability

Containers are enablers for application scaling because they make it easy to start additional instances of an application. Orchestration tools like Kubernetes automate scaling based on traffic and resource usage, enabling efficient use of resources and responding to spikes in demand. Containerization also supports a microservices architecture where services need to be independently scaled.

How Containerized Applications Work: 5 Components of a Containerized Environment 

Here’s an overview of the main components of a containerized application environment. For simplicity, in the diagram below we do not show container orchestrators.

1. Infrastructure

In a containerized application environment, the infrastructure serves as a foundational layer on which everything operates. This can range from physical servers in a data center to virtual machines in the cloud. The key characteristic of this infrastructure is its ability to be abstracted away through containerization technology, enabling applications to run consistently across various environments.

Modern infrastructure for containerized applications often involves cloud services, which provide scalability, flexibility, and high availability. Cloud providers offer managed services that complement containerization, such as databases, messaging queues, and storage, which can be seamlessly integrated into containerized applications.

2. Operating System

The operating system (OS) manages hardware resources and provides services for computer programs. In a containerized environment, the OS plays a crucial role by hosting the container engine and enabling containers to share the same kernel. This sharing mechanism is what makes containers lightweight compared to virtual machines, which require a full OS for each instance. The OS ensures process and resource isolation for containers, which is critical for security and stability.

The choice of operating system can impact the performance and compatibility of containerized applications. Linux is a popular choice due to its support for container technologies like Docker and its lightweight nature. Windows also supports containers, enabling applications that rely on Windows-specific technologies to be containerized.

3. Container Engine

The container engine is the software that enables the creation, execution, and management of containers. It acts as the runtime environment for containers, providing the necessary tools to build container images, run containers, and manage their lifecycle. Docker is one of the most well-known container engines, recognized for its simplicity and wide adoption. It provides a platform for managing containerized applications, including image creation, networking, and basic orchestration.

Container engines are designed to work closely with the operating system to utilize its kernel and manage resources efficiently. They encapsulate applications and their dependencies into containers, ensuring that they are portable and consistent across different environments. Additionally, container engines often include features for networking, volume management, and security.

4. Application and Dependencies

In a containerized application, the application code and its dependencies are packaged together in a container image. This image includes everything the application needs to run, such as specific versions of libraries, configuration files, and environment variables. It simplifies dependency management, as each container can have its unique set of dependencies without conflicting with other applications or requiring complex setup on the host system.

This approach also facilitates version control and rollback. Developers can easily update applications by building new images and can revert to previous versions if necessary. It supports a modular architecture, where applications are broken down into smaller, independent services.

5. Container Orchestrators

Container orchestrators automate the deployment, scaling, and management of containerized applications. Kubernetes, a widely used open-source platform, provides powerful features for container orchestration, including automated rollouts and rollbacks, scaling, and self-healing. 

Orchestrators manage the lifecycle of containers across a cluster of machines, ensuring that applications are always running as intended, efficiently distributing resources, and balancing loads. Orchestrators also manage networking between containers, enabling communication within a distributed application architecture. They handle service discovery, allowing containers to find and communicate with each other. They also offer robust security features, including secrets management and network policies.

Use Cases of Containerization

Here are some examples of situations where containerization is useful.

Isolating the Development Infrastructure 

Containerization plays a pivotal role in creating isolated development environments, ensuring that developers can work on individual components without affecting the overall system. Containers encapsulate the necessary dependencies and configurations, allowing developers to focus on coding rather than spending time setting up environments.

Ensuring Different Environments Are Consistent

The use of containers ensures consistency across different environments, from development and testing to staging and production. By packaging applications with their dependencies, containers eliminate the variations that often arise due to differences in underlying operating systems or software versions.  This simplifies the process of debugging and troubleshooting, as issues can be replicated and resolved in development before reaching production.

Leveraging Microservices

Containerized applications support the microservices architecture by allowing services to be deployed and scaled independently. This architectural style enhances agility, allowing for faster updates and feature rollouts. Containers encapsulate microservices, ensuring isolated environments. This simplifies the management of multiple services and their dependencies.

Building Lightweight Applications

Containers are particularly effective for building and deploying lightweight, stateless applications. Stateless applications, which do not retain any internal state between sessions, benefit from the ephemeral nature of containers. These applications can be easily scaled up or down by adding or removing container instances, making them ideal for handling varying loads. 

Making Legacy Applications Portable 

Containerization offers a pathway to modernizing legacy applications, making them more portable and easier to manage. By containerizing an older application, it can be run on modern infrastructure without the need for extensive rewrites or adjustments to the underlying code. This can extend the life of legacy systems and ease the transition to cloud-native architecture.

Implementing CI/CD Pipelines

Containers integrate seamlessly into Continuous Integration and Continuous Deployment (CI/CD) pipelines. They provide consistent environments for development, testing, and production, making it easy to move applications between environments. Automating pipelines with containers speeds up development cycles and ensures reliable deliveries. 

Enabling Batch Processing

Containers are suitable for repetitive tasks like batch processing or data analysis. By encapsulating the job in a container, it can quickly be executed on-demand or on a schedule without configuring the environment each time. This use case leverages the portability and scalability of containers to efficiently process tasks in parallel or on various infrastructures.

The Challenges of Containerized Applications 

While containerization offers many benefits, it can also introduce some challenges to the development process.

Complexity

Introducing containerized applications into an organization’s technology stack can significantly increase complexity, particularly for teams new to the concept. The abstraction layers that make containers so flexible and portable—such as the container engine and container images—require a good understanding and solid management practices to ensure efficient operation. 

This complexity is compounded when integrating containers into existing CI/CD pipelines, networking configurations, and security protocols. Furthermore, the orchestration of containers, crucial for managing large-scale deployments, involves understanding and managing a new set of tools like Kubernetes, which are known to have a steep learning curve. For organizations, this means investing in training and potentially redefining processes to fully leverage the benefits of containerization.

Reduced Visibility

One of the challenges with containerized applications is the reduced visibility into operations and performance metrics. Containers can lead to environments where hundreds or even thousands of instances are running simultaneously across multiple hosts. Monitoring and logging at this scale, especially in a dynamic environment where containers are constantly started and stopped, can be complex. 

Traditional monitoring tools may not be equipped to handle container-specific metrics or the ephemeral nature of containers, leading to gaps in visibility. This can make it difficult to diagnose performance issues, understand dependencies, and manage resource utilization effectively. To mitigate this, organizations need to adopt monitoring and logging tools specifically designed for containerized environments, which can add to the complexity and cost of operations.

Security

Security in containerized applications introduces a unique set of challenges, primarily due to the shared nature of the underlying host OS and kernel. Containers, by design, are isolated; however, vulnerabilities in the container runtime or in the application itself can lead to breaches that potentially affect all containers on the same host. 

Additionally, the portability of containers can inadvertently spread vulnerabilities across environments if container images are not properly scanned and managed. Ensuring security requires strict management of container images, including regular updates and vulnerability scanning, as well as runtime security monitoring to detect and prevent unauthorized activities. This requires specialized security tools and practices designed for container environments.

Best Practices for Managing Containerized Applications 

Here are a few best practices that can help you manage containerized applications more effectively:

Scan Images for Vulnerabilities

Regular scanning of container images for vulnerabilities is essential for security. Automated tools integrate into CI/CD pipelines to detect issues early. Addressing vulnerabilities before deployment and regularly updating images with security patches minimizes the attack surface. Establishing policies for image management ensures a secure container ecosystem.

Secure Image Registries 

Ensuring the security of image registries is a critical aspect of managing containerized applications. Image registries, where container images are stored and retrieved, must be secured to prevent unauthorized access and tampering. Implementing access controls and authentication mechanisms helps in safeguarding the registry.

Monitor Performance and Health

Continuous monitoring of container performance and health identifies potential issues early. Tools that provide real-time metrics and alerts facilitate proactive maintenance. Monitoring should cover resource usage, response times, and error rates, among other metrics. This data informs scaling decisions and helps maintain optimal performance and availability.

Manage Resources Efficiently

Efficient resource management optimizes the use of computational power and storage, reducing costs. Limiting resources per container and running only necessary services prevent waste. Orchestration tools like Kubernetes can automate scaling based on demand, ensuring efficient resource utilization. 

Manage Configurations and Secrets

Effective management of configurations and secrets protects sensitive data and simplifies deployments across environments. Configuration as code and secrets management tools secure and automate these aspects. Storing configurations and secrets outside of container images improves security and flexibility. Using environment variables and secure secrets storage allows for easy and safe configuration changes.

Restrict Container Privileges at Runtime

Limiting the privileges of containers at runtime is essential to minimize the attack surface and enhance security. Containers should operate with the least privileges necessary to perform their functions. This approach involves running containers as non-root users whenever possible and avoiding granting them unnecessary system permissions. By restricting access to host resources and networks, the potential impact of a security breach can be significantly reduced.

Secure the Container Runtime

Securing the container runtime environment is crucial to protect against threats targeting the container infrastructure. This includes implementing security features provided by the container runtime, such as seccomp profiles and AppArmor or SELinux policies, to restrict container actions and access to system resources. Monitoring runtime activity for suspicious behavior and implementing network policies to control traffic between containers are also key practices.

Holistic Container Security with Aqua

Aqua provides a Cloud Native Application Protection Platform (CNAPP) that secures cloud native, serverless, and container technologies. Aqua offers end-to-end security for containerized applications, and protects you throughout the full lifecycle of your DevOps pipeline: from code and build, across infrastructure, and through to runtime controls, container-level firewalls, audit, and compliance.

Continuous Image Assurance

Aqua scans container images for malware, vulnerabilities, embedded secrets, configuration issues and OSS licensing. You can develop policies that outline, for example, which images can run on your container hosts. Aqua’s vulnerability database, founded on a continuously updated data stream, is aggregated from several sources and consolidated to make sure only the latest data is used, promoting accuracy and limiting false positives and negligible CVEs.

Aqua offers Trivy, an all-in one open source security scanner, which now provides multiple capabilities:

• Scanning IaC templates for security vulnerabilities
• Kubernetes operator that can automatically trigger scans in response to changes to cluster state
• Automated generation of software bills of materials (SBOMs)
• Detection of sensitive data like hard-coded secrets in code and containers
• Docker Desktop integration making it possible to scan container images directly from Docker Dashboard

Aqua DTA

Solutions like Aqua’s Dynamic Threat Analysis allow protection against advanced and evasive security threats, including supply chain attacks. The industry’s first container sandbox solution, Aqua DTA dynamically assesses the risks of container images by running them in an isolated sandbox to monitor runtime behavior before they hit the production environment.

Runtime Security for Containers

Aqua protects containerized applications at runtime, ensuring container immutability and prohibiting changes to running containers, isolating the container from the host via custom machine-learned SECCOMP profiles. It also ensures least privileges for files, executables and OS resources using a machine-learned behavioral profile, and manages network connections with a container firewall.

Drift prevention

To enforce immutability of container workloads, Aqua enables drift prevention at runtime. This capability deterministically prohibits any changes to the image after it is instantiated into a container. By identifying and blocking anomalous behavior in running containers, Aqua helps ensure that your workloads are protected from runtime attacks, zero-day exploits, and internal threats.

Aqua further enhances securing containers as follows:

• Event logging and reporting—granular audit trails of access activity, scan container commands, events, and coverage, container activity, system events, and secrets activity.
• CIS certified benchmark checks—assess node configuration against container runtime and K8s CIS benchmarks with scheduled reporting and testing or Aqua OSS tools.
• Global compliance templates—pre-defined compliance policies meet security standards such as HIPPA, CIS, PCI, and NIST.
• Full user accountability—uses granular user accountability and monitored super-user permissions.
• “Thin OS” host compliance—monitor and scan host for malware, vulnerabilities, login activity, and to identify scan images kept on hosts.
• Compliance enforcement controls—only images and workloads that pass compliance checks can run in your environment.

Container Firewall

Aqua’s container firewall lets you visualize network connections, develop rules based on application services, and map legitimate connections automatically. Only whitelisted connections will be allowed, both within a container cluster, and also between clusters.

Secrets Management

Store your credentials as secrets, don’t leave them in your source code. Aqua securely transfers secrets to containers at runtime, encrypted at rest and in transit, and places them in memory with no persistence on disk, so they are only visible to the relevant container. Integrate Aqua’s solution with your current enterprise vault, including CyberArk, Hashicorp, AWS KMS or Azure Vault. You can revoke, update, and rotate secrets without restarting containers.
Learn more about Aqua Container Security