Browser Performance Testing

If your application offers a web interface and you’re using GitLab CI/CD, you can quickly determine the rendering performance impact of pending code changes in the browser.

Overview

GitLab uses Sitespeed.io, a free and open source tool, for measuring the rendering performance of web sites. The Sitespeed plugin that GitLab built outputs the performance score for each page analyzed in a file called browser-performance.json this data can be shown on Merge Requests.

Use cases

Consider the following workflow:

  1. A member of the marketing team is attempting to track engagement by adding a new tool.
  2. With browser performance metrics, they see how their changes are impacting the usability of the page for end users.
  3. The metrics show that after their changes, the performance score of the page has gone down.
  4. When looking at the detailed report, they see the new JavaScript library was included in <head>, which affects loading page speed.
  5. They ask for help from a front end developer, who sets the library to load asynchronously.
  6. The frontend developer approves the merge request, and authorizes its deployment to production.

How browser performance testing works

First, define a job in your .gitlab-ci.yml file that generates the Browser Performance report artifact. GitLab then checks this report, compares key performance metrics for each page between the source and target branches, and shows the information in the merge request.

For an example Performance job, see Configuring Browser Performance Testing.

Note: If the Browser Performance report has no data to compare, such as when you add the Browser Performance job in your .gitlab-ci.yml for the very first time, the Browser Performance report widget won’t show. It must have run at least once on the target branch (master, for example), before it will display in a merge request targeting that branch.

Browser Performance Widget

Configuring Browser Performance Testing

This example shows how to run the sitespeed.io container on your code by using GitLab CI/CD and sitespeed.io using Docker-in-Docker.

  1. First, set up GitLab Runner with a Docker-in-Docker build.
  2. Configure the default Browser Performance Testing CI job as follows in your .gitlab-ci.yml file:

    include:
      template: Verify/Browser-Performance.gitlab-ci.yml
    
    performance:
      variables:
        URL: https://example.com
    
Note: For versions before 12.4, see the information for older GitLab versions. If you are using a Kubernetes cluster, use template: Jobs/Browser-Performance-Testing.gitlab-ci.yml instead.

The above example creates a performance job in your CI/CD pipeline and runs sitespeed.io against the webpage you defined in URL to gather key metrics.

The example uses a CI/CD template that is included in all GitLab installations since 12.4, but it will not work with Kubernetes clusters. If you are using GitLab 12.3 or older, you must add the configuration manually

The template uses the GitLab plugin for sitespeed.io, and it saves the full HTML sitespeed.io report as a Browser Performance report artifact that you can later download and analyze. This implementation always takes the latest Browser Performance artifact available. If GitLab Pages is enabled, you can view the report directly in your browser.

You can also customize the jobs with environment variables:

  • SITESPEED_IMAGE: Configure the Docker image to use for the job (default sitespeedio/sitespeed.io), but not the image version.
  • SITESPEED_VERSION: Configure the version of the Docker image to use for the job (default 13.3.0).
  • SITESPEED_OPTIONS: Configure any additional sitespeed.io options as required (default nil). Refer to the sitespeed.io documentation for more details.

For example, you can override the number of runs sitespeed.io makes on the given URL, and change the version:

include:
  template: Verify/Browser-Performance.gitlab-ci.yml

performance:
  variables:
    URL: https://www.sitespeed.io/
    SITESPEED_VERSION: 13.2.0
    SITESPEED_OPTIONS: -n 5

Configuring degradation threshold

Introduced in GitLab 13.0.

You can configure the sensitivity of degradation alerts to avoid getting alerts for minor drops in metrics. This is done by setting the DEGRADATION_THRESHOLD variable. In the example below, the alert will only show up if the Total Score metric degrades by 5 points or more:

include:
  template: Verify/Browser-Performance.gitlab-ci.yml

performance:
  variables:
    URL: https://example.com
    DEGRADATION_THRESHOLD: 5

The Total Score metric is based on sitespeed.io’s coach performance score. There is more information in the coach documentation.

Performance testing on Review Apps

The above CI YAML configuration is great for testing against static environments, and it can be extended for dynamic environments, but a few extra steps are required:

  1. The performance job should run after the dynamic environment has started.
  2. In the review job:
    1. Generate a URL list file with the dynamic URL.
    2. Save the file as an artifact, for example with echo $CI_ENVIRONMENT_URL > environment_url.txt in your job’s script.
    3. Pass the list as the URL environment variable (which can be a URL or a file containing URLs) to the performance job.
  3. You can now run the sitespeed.io container against the desired hostname and paths.

Your .gitlab-ci.yml file would look like:

stages:
  - deploy
  - performance

include:
  template: Verify/Browser-Performance.gitlab-ci.yml

review:
  stage: deploy
  environment:
    name: review/$CI_COMMIT_REF_SLUG
    url: http://$CI_COMMIT_REF_SLUG.$APPS_DOMAIN
  script:
    - run_deploy_script
    - echo $CI_ENVIRONMENT_URL > environment_url.txt
  artifacts:
    paths:
      - environment_url.txt
  only:
    - branches
  except:
    - master

performance:
  dependencies:
    - review
  variables:
    URL: environment_url.txt

GitLab versions 12.3 and older

Browser Performance Testing has gone through several changes since it’s introduction. In this section we’ll detail these changes and how you can run the test based on your GitLab version:

  • In GitLab 12.4 a job template was made available.
  • In 13.2 the feature was renamed from Performance to Browser Performance with additional template variables. The job name in the template is still performance for compatibility reasons, but may be renamed to match in a future iteration.
  • For 11.5 to 12.3 no template is available and the job has to be defined manually as follows:
performance:
  stage: performance
  image: docker:git
  variables:
    URL: https://example.com
    SITESPEED_VERSION: 13.3.0
    SITESPEED_OPTIONS: ''
  services:
    - docker:stable-dind
  script:
    - mkdir gitlab-exporter
    - wget -O ./gitlab-exporter/index.js https://gitlab.com/gitlab-org/gl-performance/raw/master/index.js
    - mkdir sitespeed-results
    - docker run --shm-size=1g --rm -v "$(pwd)":/sitespeed.io sitespeedio/sitespeed.io:$SITESPEED_VERSION --plugins.add ./gitlab-exporter --outputFolder sitespeed-results $URL $SITESPEED_OPTIONS
    - mv sitespeed-results/data/performance.json performance.json
  artifacts:
    paths:
      - performance.json
      - sitespeed-results/
    reports:
      performance: performance.json
  • For 11.4 and earlier the job should be defined as follows:
performance:
  stage: performance
  image: docker:git
  variables:
    URL: https://example.com
  services:
    - docker:stable-dind
  script:
    - mkdir gitlab-exporter
    - wget -O ./gitlab-exporter/index.js https://gitlab.com/gitlab-org/gl-performance/raw/master/index.js
    - mkdir sitespeed-results
    - docker run --shm-size=1g --rm -v "$(pwd)":/sitespeed.io sitespeedio/sitespeed.io:6.3.1 --plugins.add ./gitlab-exporter --outputFolder sitespeed-results $URL
    - mv sitespeed-results/data/performance.json performance.json
  artifacts:
    paths:
      - performance.json
      - sitespeed-results/

Upgrading to the latest version and using the templates is recommended, to ensure you receive the latest updates, including updates to the sitespeed.io versions.