The Complete Guide to Container Monitoring

The use of containers has become increasingly popular in recent years. Containerized applications offer many benefits, including resource efficiency, portability, and the ability for development and DevOps teams to develop, manage, and deploy applications faster and more securely.

Container monitoring can also help ensure the reliability, security and performance of containerized applications, as the use of highly distributed container environments presents new challenges for performance monitoring and troubleshooting. Container monitoring can provide the visibility needed to take full advantage of container environments.

Checkmk dashboard for monitoring Kubernetes clusters

What is container monitoring?

Container monitoring includes monitoring of the containers themselves as well as the nodes on which the containers are running. It allows you to track metrics related to the performance and health of containerized applications. Monitoring insights can also be used to efficiently scale the container environment.

Typical metrics checked by container monitoring tools include the total number of containers, container memory, and CPU utilization. Monitoring solutions with automatic service discovery and the ability to automatically add or remove containers for monitoring can greatly simplify monitoring.

Powerful all-in-one monitoring tools such as Checkmk provide all needed insights that allow you to make the best use of your static and dynamic IT stacks.

Who uses container monitoring?

The density of containerized applications and runtimes is on the rise. Small and large organizations use containerized environments in their DevOps application deployment strategies. 

Docker is currently the most popular platform for building, deploying, and managing containers. More than 13 million developers use Docker for more than 7 million applications.

And Kubernetes has rapidly become the most popular platform for managing containerized workloads and services. As of 2021, over 50% of organizations worldwide have adopted Kubernetes.
To ensure smooth operation of the container environment, companies that use containers should also monitor them.

Why monitor your containers?

Container monitoring can be used to track the performance of container environments. For example, you can use the information provided by a container monitoring solution to identify bottlenecks and resource issues, determine if containers are undersized or oversized, detect problems and failures in applications, or ensure that an orchestration tool's dynamic scaling is working properly, and that loads are distributed evenly across containers.

Container monitoring should always be part of a comprehensive monitoring system that provides visibility into the entire IT infrastructure. This allows organizations to better understand their IT and link the performance of containers to the performance of other IT services. Monitoring containers not only helps to manage existing and potential problems, but also to continuously optimize the deployment. The result is better application performance and uptime, and a better user experience.

Challenges faced when monitoring containers

The benefits for deploying containers are obvious. At the same time, the natural behavior of containers requires a different approach to monitoring than physical hardware. While retrieving data, monitoring status, and setting thresholds are the same for both types of deployments, that's about it. Containers are ephemeral and can have a lifespan of only a few seconds, making it difficult to track changes. Containers also share resources, making it difficult to know the health of an application and the performance of containers.

The main challenges in monitoring containers are:

  • Tracking containers throughout their lifecycle.
  • Scaling monitoring as the container environment grows.
  • Checking the resource usage of individual containers and shared resources such as storage.
  • Defining reasonable thresholds for alerting on problems.

To overcome these challenges, container monitoring requires solutions that have the following features, among others:

  • Automatic detection to discover new containers and add them to monitoring.
  • Automatic inventory of all hardware and software aspects of nodes and containers.
  • Simple scalability of the monitoring.
  • Recording of performance metrics such as CPU utilization, memory, or network transfer rates of the individual containers.
  • Visual representation of metrics for easier problem detection.
  • Support for orchestration tools such as Kubernetes or Docker Swarm or cloud platforms on which containers are hosted.
Screenshot of a EKS cluster dashboard in Checkmk

How does container monitoring work?

There are two ways to monitor containers. One is to use the command line of orchestration platforms, such as Docker or Kubernetes, to access logs and information about the containers. This gives you a basic overview, and you can use the logs to analyze possible causes of errors. However, the main drawback is that manual monitoring is inefficient and time-consuming, and it's easy to lose track. In addition, this method does not provide alerts when problems occur.

The second option is to use a monitoring solution that is designed specifically for container monitoring and that provides all the necessary visibility into container resource usage along with features such as historical data analysis, data visualization, and alerting.

How can you monitor containers in Docker?

The Docker command line includes some commands that you can use for container monitoring:

  • The docker stats [OPTIONS] [CONTAINER...] command displays real-time resource usage statistics for all running containers, providing insight into CPU, memory usage, memory limit, and network IO metrics. If you wish to focus on specific container(s), you can specify a list of container names or IDs separated by spaces.
  • You can view the running container list using the docker ps [OPTIONS]. Use the -all command to show all containers.
  • You can use the docker top CONTAINER [ps OPTIONS] command to view the processes for a specific container.

Alternatively, Docker containers can be monitored with a monitoring solution. The benefits of dedicated container monitoring software include:

  • Detailed information about the performance and resource usage of Docker nodes and containers. For example, CPU utilization, memory usage, and disk I/O.
  • Visualization of key metrics in dashboards.
  • Contextual information for effective root cause analysis and complex problem-solving.
  • Storage of historical data to analyze trends or changes in the Docker topology.
  • Alerts on critical events or anomalies in the container environment.

For example, Checkmk uses an agent to obtain detailed information about the Docker node and every single container.

How can you monitor containers in Kubernetes?

Kubernetes provides the ability to monitor containers through the metrics server. This makes it possible to retrieve a limited set of metrics, such as CPU and memory utilization, via the Kubernetes Metrics API. With the Kubernetes Dashboard, the container platform also offers a web-based user interface that provides a convenient way to manage and monitor the containerized applications in a Kubernetes cluster once deployed.

It allows users to deploy and troubleshoot applications, as well as manage cluster resources. Kubernetes Dashboard provides an overview of all running applications in the cluster and allows users to create and modify Kubernetes resources such as deployments, jobs, and daemon sets. In addition, the Kubernetes Dashboard enables actions such as scaling a deployment, initiating a rolling update, restarting a pod, or deploying new applications. It also provides visibility into a cluster's resources and errors that have occurred.

Kubernetes Dashboard also stores historical data, although more limited in quantity and scope than a monitoring solution like Checkmk. Dedicated Kubernetes monitoring software, such as Checkmk, can provide more comprehensive monitoring capabilities.
Checkmk uses the API server to get basic information about the cluster. The Checkmk Node Collector and the Checkmk Cluster Collector, which provides information about how much memory a DaemonSet is currently consuming, provide a comprehensive picture.

Checkmk monitors the clusters, nodes, deployments, pods, DaemonSets, and StatefulSets of a Kubernetes environment, providing key metrics such as CPU, memory, file systems, disk I/O, kernel performance, and threads. Kubernetes monitoring with Checkmk also provides intelligent alerting and a wealth of contextual information for troubleshooting.

Critical alerts of a Kubernetes cluster in Checkmk including details

What container monitoring system features are important?

When evaluating a container monitoring solution, the following aspects should be considered 
Real-time monitoring of all key metrics in the container environment for immediate detection of problematic states of existing applications or identification of CPU or memory bottlenecks, instabilities, or heavy consumers.

  • Support for monitoring all components of the container platform in use, including clusters, nodes, deployments, pods, DaemonSets, and StatefulSet for Kubernetes.
  • Precise alerting when real problems occur, including detailed root cause information.
  • Visualize data for easier analysis of dynamic relationships.

Final thoughts

The widespread adoption and growth of containers is a testament to their benefits to developers, organizations, and users. Monitoring plays a critical role in ensuring the availability, performance, and security of containerized workloads.

It is important to use a monitoring solution like Checkmk that can handle the unique requirements of container applications.


What are Docker container logs?

Docker automatically generates output and error streams for containers. Docker container logs aggregate these output streams. You can analyze Docker container logs to evaluate container performance and health.

What is container resource monitoring?

Container resource monitoring refers to measuring host resources (CPU, memory, network, storage, etc.) used by a container during its lifetime. You can monitor the resource usage of individual containers and the total resource usage of all containers running on a node. The advantage of container resource monitoring is that it allows you to be proactive. Instead of reacting to resource unavailability that leads to performance degradation, you can add or free up resources well in time so that your container and application performance are unaffected.

What do we mean when we say that containers are 'ephemeral' in nature?

The "ephemeral" nature of containers refers to the fact that provisioning and destroying a container is a swift process. After starting, a container lasts for as long as required and is then destroyed by the container orchestration scheduler.