Load testing is very important to check application performance during heavy traffic or sudden traffic spikes. This post will help to understand load testing using Docker containers with Continuous Integration (CI) tools.  The Docker approach to load test applications enables sharing the tests between users and replicating the test environment easily using Docker containers. We will briefly explain what Docker is and using Docker containers and tools used to load test applications via CI.


What is Docker?

Docker! You might have heard this fascinating word among your team or read in technology blogs and it also might sound intimidating at first place. Docker is a containerization platform which packages your app source code and all the dependency packages together in a form called a Docker container. It makes sure the application runs in any environment without thinking about the overhead of operating system or system configurations. Isn’t this cool!

Moreover, Docker is a popular tool which makes it very easy to build, deploy and run applications using containers. Due to this, our application can run anywhere with having the same behavior. And the important thing, Docker is open source.


What is a Docker Container?

A Docker container is a lightweight, standalone, executable package of software that includes everything which an application needs: codebase, system libraries, system tools and settings.  A container wraps up the code and its dependencies together which helps the application to run quickly and reliably from one environment to another.


With Docker, developers can focus on writing code without worrying about the system on which application runs, this makes the application portable. The way an application runs on your local machine would be as close or same to production.


Key Features of Docker

  • Easily scalable.  Due to the lightweight containers, docker containers can spin up in seconds and can easily scale.
  • Increases productivity.  It eases technical overhead for application development, environment setup. Moreover it helps to execute the application in an isolated environment and reduces use of resources.
  • Application isolation.  Each application runs independent to each other and runs applications in isolation.
  • Reduced infrastructure and maintenance costs.  It helps supporting existing platforms to be moved to Docker easily, which runs in an automated manner hence reducing maintenance costs.
  • Swarm.  Swarm is a clustering and scheduling tool for Docker containers. It allows the user to manage multiple containers deployed across multiple host machines.
  • Routing mesh.  It helps in way of routing and balancing the traffic to the containers.


Benefits of Docker

  • Docker enables application portability.
  • Docker enables faster development release cycles.
  • It shines with microservice architecture.
  • Docker provides an isolation environment for applications.
  • Docker enables faster and easy horizontal scaling of applications.
  • It enables efficient use of resources


Docker Inside CI Tools

The biggest benefit with Docker is we don’t tend to worry about dependency conflicts. For example, if we want to  build one project with Golang 1.11 and one project with Golang 1.12 version, Docker can help to segregate this and create images for both and even run both in parallel on different container with no conflicts, which would not be possible doing on a server. The images cooked with different versions can be saved to registry and can be used as part of continuous integration tools like Jenkins.

Jenkins provides support in this case, where it picks available Docker images built for performance test or integration test and overhead for cooking Docker images from scratch is saved. Docker layer caching saves a lot of time here. As part of our CI pipeline, we need to create a Docker image for a performance test and this image can be run using CI to carry out a performance test of application. We can even automate this step, with every feature addition or change, we can run a performance test to benchmark and safeguard performance impact due to recent changes.


Limitations of Using Docker for Performance Tests

While Docker has many advantages, it has couple of limitations while doing performance test:

  • When we run a heavy load test simulation using multiple Docker containers on the same machine, it can consume a lot of CPU of the running server, which can affect our test results.
  • Performance testing report via Docker lacks enough application details.
  • We may need to fine tune host OS and containers where performance tests are running.
  • As Docker containers are disposable, it may lead to loss of report.

To save us from all these limitations, we can use a solution like LoadView, which can be easily integrated with Jenkins and helps stress test websites, web applications, and APIs with thousands of concurrent connections in real browsers from a fully managed cloud.


LoadView Performance Test Integration with Jenkins

Whenever we test any application, we test if it’s functionally working as expected. If that works we mark the application’s functionality is working fine. But in the real world, the same application is used by multiple users which can have its own complications. We need to validate whether our application is able to handle such traffic.  So with every change or new feature development, we can run stress tests on the application via our LoadView plugin which can be integrated with Jenkins.

Let’s look forward for steps to run load tests via Jenkins integrated with LoadView:

  1. Before, we start using a LoadView Load Test Scenario to test your build in Jenkins, we need to have a Test Scenario on LoadView, where we can add a list of APIs which needs to be stress tested.
  2. To start integration with Jenkins, we need a LoadView Unique identifier to use as LoadView Security token.
  3. In LoadView, create an integration UID under Account > Integrations > Add Integration > Load Testing Web API. Copy this integration UID to use in Jenkins.

Docker Integration UIDs


  1. To set the stress test, we would need Test Scenario Id. The Scenario ID can be found on the scenario setup page or on the test’s History page (Test Manager > the test’s actions menu > History).

Docker load test scenario


Configuring LoadView Plugin in Jenkins

To configure the LoadView plugin:

  1. Log into your Jenkins account.
  2. In Jenkins, go to Credentials > Add Credentials > LoadView Security Token (UID). Configure and validate the credentials:
  • Kind: LoadView Security Token (UID).
  • Scope: select Global.
  • ID: leave the default or specify a unique ID.
  • Description: specify a unique description to distinguish the credentials.
  • UID: paste the Load Testing Web API UID from your LoadView account. Once the UID has been added, click Validate UID to make sure Jenkins can access the LoadView API.

3. Next, select a job and click Configure

Docker Jenkins


  1. Go to Build > Post-build Actions > Add post-build action > LoadView-Run load test scenario. Specify LoadView Stress Test settings for the build:
  • Credentials: select the API key using the description.
  • Scenario ID: paste the test scenario ID you want to use in the build. Copy the ID from the scenario page in LoadView.
  • Error Threshold: specify an acceptable percentage of sessions with errors that occurred while testing (failed to access the target resource, no keywords/image found, etc.). If the percentage of error sessions is greater than the specified value, the build will be marked as a failure in Jenkins.
  • Average Time: specify a limit for an average response time measured during test execution. If the limit is reached, the build will be marked as a failure in Jenkins.
  1. Click Save.

View Test Results:

When a stress test is running, the status is displayed in the Jenkins Console Output in real-time mode.

Jenkins console output


Jenkins performance results


Docker Application Load Testing: Wrap Up

While Docker has many advantages, there can be limitations when executing load tests with heavy load, such as consuming a lot of CPU on the server, when using multiple Docker containers on the same machine, which can dramatically affect the test results. With a solution like LoadView, which can be easily integrated with CI tools like Jenkins, we can create and manage load tests with thousands of concurrent connections from a fully managed cloud.

Try the LoadView platform today and get $20 in load testing credits to get started.