Distributed Load Testing Using Kubernetes
In this lab you will learn how to use Kubernetes Engine to deploy a distributed load testing framework. The framework uses multiple containers to create load testing traffic for a simple REST-based API. Although this solution tests a simple web application, the same pattern can be used to create more complex load testing scenarios such as gaming or Internet-of-Things (IoT) applications. This solution discusses the general architecture of a container-based load testing framework.
System under test
For this lab the system under test is a small web application deployed to Google App Engine. The application exposes basic REST-style endpoints to capture incoming HTTP POST requests (incoming data is not persisted).
The application that you'll deploy is modeled after the backend service component found in many Internet-of-Things (IoT) deployments. Devices first register with the service and then begin reporting metrics or sensor readings, while also periodically re-registering with the service.
Common backend service component interaction looks like this:
To model this interaction, you'll use
Locust, a distributed, Python-based load testing tool that is capable of distributing requests across multiple target paths. For example, Locust can distribute requests to the
/metrics target paths.
The workload is based on the interaction described above and is modeled as a set of Tasks in Locust. To approximate real-world clients, each Locust task is weighted. For example, registration happens once per thousand total client requests.
The Locust container image is a Docker image that contains the Locust software.
container clusterconsists of at least one cluster master and multiple worker machines called nodes. These master and node machines run the Kubernetes cluster orchestration system. For more information about clusters, see the Kubernetes Engine documentation
podis one or more containers deployed together on one host, and the smallest compute unit that can be defined, deployed, and managed. Some pods contain only a single container. For example, in this lab, each of the Locust containers runs in its own pod.
replication controllerensures that a specified number of pod "replicas" are running at any one time. If there are too many, the replication controller kills some pods. If there are too few, it starts more. This lab has three replication controllers: one ensures the existence of a single DNS server pod; another maintains a single Locust master pod; and a third keeps exactly 10 Locust worker pods running.
A particular pod can disappear for a variety of reasons, including node failure or intentional node disruption for updates or maintenance. This means that the IP address of a pod does not provide a reliable interface for that pod. A more reliable approach would use an abstract representation of that interface that never changes, even if the underlying pod disappears and is replaced by a new pod with a different IP address. A Kubernetes Engine
serviceprovides this type of abstract interface by defining a logical set of pods and a policy for accessing them.
In this lab there are several services that represent pods or sets of pods. For example, there is a service for the DNS server pod, another service for the Locust master pod, and a service that represents all 10 Locust worker pods.
The following diagram shows the contents of the master and worker nodes:
What you'll do
- Create a system under test i.e. a small web application deployed to Google App Engine.
- Use Kubernetes Engine to deploy a distributed load testing framework
- Create load testing traffic for a simple REST-based API.
- Familiarity with PYTHON
- Familiarity with standard Linux text editors such as Vim, Emacs or Nano
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