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Docker images for the Selenium Grid Server

The project is made possible by volunteer contributors who have put in thousands of hours of their own time, and made the source code freely available under the Apache License 2.0.

These Docker images come with a handful of tags to simplify its usage, have a look at them in one of our releases.

To get notifications of new releases, add yourself as a "Releases only" watcher.

These images are published to the Docker Hub registry at Selenium Docker Hub.

Community

Do you need help to use these Docker images? Talk to us at https://www.selenium.dev/support/

Contents

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Quick start

  1. Start a Docker container with Firefox
docker run -d -p 4444:4444 -p 7900:7900 --shm-size="2g" selenium/standalone-firefox:4.26.0-20241101

  1. Point your WebDriver tests to http://localhost:4444

  2. That's it!

  3. (Optional) To see what is happening inside the container, head to http://localhost:7900/?autoconnect=1&resize=scale&password=secret.

For more details about visualising the container activity, check the Debugging section.

:point_up: When executing docker run for an image that contains a browser please use the flag --shm-size=2g to use the host's shared memory.

:point_up: Always use a Docker image with a full tag to pin a specific browser and Grid version. See Tagging Conventions for details.

Try them out in a ready-to-use GitPod environment!

Open in Gitpod

Experimental Multi-Arch amd64/aarch64/armhf Images

From image tag based 4.21.0 onwards, the architectures supported by this project are as below:

ArchitectureAvailable
x86_64 (aka amd64)✅
aarch64 (aka arm64/armv8)✅
armhf (aka arm32/armv7l)❌

Browser images in multi-arch

The following browsers are available in multi-arch images:

ArchitectureChromeChromiumFirefoxEdge
x86_64 (aka amd64)✅✅✅✅
aarch64 (aka arm64/armv8)❌✅✅❌
armhf (aka arm32/armv7l)❌❌❌❌

Note:

$ docker run --rm -it -p 4444:4444 -p 5900:5900 -p 7900:7900 --shm-size 2g selenium/standalone-chromium:latest

Multi-arch images are tested on CircleCI with resource class Linux/ARM64. See the status below.

CircleCI

History of the multi-arch images

For experimental docker container images, which run on platforms such as the Apple M-series or Raspberry Pi, the repository at seleniumhq-community/docker-seleniarm provided images which are published on the Seleniarm Docker Hub registry.

See issue #1076 for more information on these images.

Now, the fork seleniumhq-community/docker-seleniarm was merged.

Build the multi-arch images locally

We recommend to enable the experimental feature containerd image store in Docker Engine. containerd understands multiplatform images, where a single image tag can refer to different variants covering a range of OS and hardware architectures. It simplifies the process of building, storing, and distributing images across different platforms.

A single command to enable that feature in Docker Engine:

make set_containerd_image_store

To build all the images for multiplatform, run the following command:

PLATFORMS=linux/amd64,linux/arm64 make build

To build the images for a specific platform, run the following command:

PLATFORMS=linux/arm64 make build

By default, without specifying the PLATFORMS variable, the images are built for the linux/amd64 platform.

Nightly Images

Nightly images are built on top of the Nightly build on the upstream project Selenium with the latest changes on main branch in this repository. The image tag is nightly. This is not recommended to use images in production. It is only for testing purpose.

$ docker run -d -p 4442-4444:4442-4444 --name selenium-hub selenium/hub:nightly

Check out the docker compose to get started with Nightly images docker-compose-v3-full-grid-nightly.yml

Dev and Beta Channel Browser Images

To run tests or otherwise work with pre-release browsers, Google, Mozilla, and Microsoft maintain a Dev and Beta release channel for those who need to see what's soon to be released to the general population.

Dev and Beta Standalone Mode

Here are the instructions to run them in Standalone mode:

Chrome Beta:

$ docker run --rm -it -p 4444:4444 -p 7900:7900 --shm-size 2g selenium/standalone-chrome:beta

Chrome Dev:

$ docker run --rm -it -p 4444:4444 -p 7900:7900 --shm-size 2g selenium/standalone-chrome:dev

Firefox Beta:

$ docker run --rm -it -p 4444:4444 -p 7900:7900 --shm-size 2g selenium/standalone-firefox:beta

Firefox Dev:

$ docker run --rm -it -p 4444:4444 -p 7900:7900 --shm-size 2g selenium/standalone-firefox:dev

Edge Beta:

$ docker run --rm -it -p 4444:4444 -p 7900:7900 --shm-size 2g selenium/standalone-edge:beta

Edge Dev:

$ docker run --rm -it -p 4444:4444 -p 7900:7900 --shm-size 2g selenium/standalone-edge:dev

Dev and Beta on the Grid

docker-compose-v3-beta-channel.yml:

# To execute this docker compose yml file use `docker compose -f docker-compose-v3-beta-channel.yml up`
# Add the `-d` flag at the end for detached execution
# To stop the execution, hit Ctrl+C, and then `docker compose -f docker-compose-v3-beta-channel.yml down`
version: "3"
services:
  chrome:
    image: selenium/node-chrome:beta
    shm_size: 2gb
    depends_on:
      - selenium-hub
    environment:
      - SE_EVENT_BUS_HOST=selenium-hub
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443

  edge:
    image: selenium/node-edge:beta
    shm_size: 2gb
    depends_on:
      - selenium-hub
    environment:
      - SE_EVENT_BUS_HOST=selenium-hub
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443

  firefox:
    image: selenium/node-firefox:beta
    shm_size: 2gb
    depends_on:
      - selenium-hub
    environment:
      - SE_EVENT_BUS_HOST=selenium-hub
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443

  selenium-hub:
    image: selenium/hub:latest
    container_name: selenium-hub
    ports:
      - "4442:4442"
      - "4443:4443"
      - "4444:4444"

docker-compose-v3-dev-channel.yml:

# To execute this docker compose yml file use `docker compose -f docker-compose-v3-dev-channel.yml up`
# Add the `-d` flag at the end for detached execution
# To stop the execution, hit Ctrl+C, and then `docker compose -f docker-compose-v3-dev-channel.yml down`
version: "3"
services:
  chrome:
    image: selenium/node-chrome:dev
    shm_size: 2gb
    depends_on:
      - selenium-hub
    environment:
      - SE_EVENT_BUS_HOST=selenium-hub
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443

  edge:
    image: selenium/node-edge:dev
    shm_size: 2gb
    depends_on:
      - selenium-hub
    environment:
      - SE_EVENT_BUS_HOST=selenium-hub
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443

  firefox:
    image: selenium/node-firefox:dev
    shm_size: 2gb
    depends_on:
      - selenium-hub
    environment:
      - SE_EVENT_BUS_HOST=selenium-hub
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443

  selenium-hub:
    image: selenium/hub:latest
    container_name: selenium-hub
    ports:
      - "4442:4442"
      - "4443:4443"
      - "4444:4444"

For more information on the Dev and Beta channel container images, see the blog post on Dev and Beta Channel Browsers via Docker Selenium.

Execution modes

Standalone

Firefox Firefox

docker run -d -p 4444:4444 --shm-size="2g" selenium/standalone-firefox:4.26.0-20241101

Chrome Chrome

docker run -d -p 4444:4444 --shm-size="2g" selenium/standalone-chrome:4.26.0-20241101

Edge Edge

docker run -d -p 4444:4444 --shm-size="2g" selenium/standalone-edge:4.26.0-20241101

Note: Only one Standalone container can run on port 4444 at the same time.

Hub and Nodes

There are different ways to run the images and create a Grid with a Hub and Nodes, check the following options.

Docker networking

The Hub and Nodes will be created in the same network and they will recognize each other by their container name. A Docker network needs to be created as a first step.

macOS/Linux
$ docker network create grid
$ docker run -d -p 4442-4444:4442-4444 --net grid --name selenium-hub selenium/hub:4.26.0-20241101
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub \
    --shm-size="2g" \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    selenium/node-chrome:4.26.0-20241101
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub \
    --shm-size="2g" \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    selenium/node-edge:4.26.0-20241101
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub \
    --shm-size="2g" \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    selenium/node-firefox:4.26.0-20241101
Windows PowerShell
$ docker network create grid
$ docker run -d -p 4442-4444:4442-4444 --net grid --name selenium-hub selenium/hub:4.26.0-20241101
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub `
    --shm-size="2g" `
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 `
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 `
    selenium/node-chrome:4.26.0-20241101
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub `
    --shm-size="2g" `
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 `
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 `
    selenium/node-edge:4.26.0-20241101
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub `
    --shm-size="2g" `
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 `
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 `
    selenium/node-firefox:4.26.0-20241101

When you are done using the Grid, and the containers have exited, the network can be removed with the following command:

# Removes the grid network
$ docker network rm grid

Using different machines/VMs

The Hub and Nodes will be created on different machines/VMs, they need to know each other's IPs to communicate properly. If more than one node will be running on the same Machine/VM, they must be configured to expose different ports.

Hub - Machine/VM 1
$ docker run -d -p 4442-4444:4442-4444 --name selenium-hub selenium/hub:4.26.0-20241101
Node Chrome - Machine/VM 2
macOS/Linux
$ docker run -d -p 5555:5555 \
    --shm-size="2g" \
    -e SE_EVENT_BUS_HOST=<ip-from-machine-1> \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    -e SE_NODE_HOST=<ip-from-machine-2> \
    selenium/node-chrome:4.26.0-20241101
Windows PowerShell
$ docker run -d -p 5555:5555 `
    --shm-size="2g" `
    -e SE_EVENT_BUS_HOST=<ip-from-machine-1> `
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 `
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 `
    -e SE_NODE_HOST=<ip-from-machine-2> `
    selenium/node-chrome:4.26.0-20241101
Node Edge - Machine/VM 3
macOS/Linux
$ docker run -d -p 5555:5555 \
    --shm-size="2g" \
    -e SE_EVENT_BUS_HOST=<ip-from-machine-1> \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    -e SE_NODE_HOST=<ip-from-machine-3> \
    selenium/node-edge:4.26.0-20241101
Windows PowerShell
$ docker run -d -p 5555:5555 `
    --shm-size="2g" `
    -e SE_EVENT_BUS_HOST=<ip-from-machine-1> `
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 `
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 `
    -e SE_NODE_HOST=<ip-from-machine-3> `
    selenium/node-edge:4.26.0-20241101
Node Firefox - Machine/VM 4
macOS/Linux
$ docker run -d -p 5555:5555 \
    --shm-size="2g" \
    -e SE_EVENT_BUS_HOST=<ip-from-machine-1> \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    -e SE_NODE_HOST=<ip-from-machine-4> \
    selenium/node-firefox:4.26.0-20241101
Windows PowerShell
$ docker run -d -p 5555:5555 `
    --shm-size="2g" `
    -e SE_EVENT_BUS_HOST=<ip-from-machine-1> `
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 `
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 `
    -e SE_NODE_HOST=<ip-from-machine-4> `
    selenium/node-firefox:4.26.0-20241101
Node Chrome - Machine/VM 4
macOS/Linux
$ docker run -d -p 5556:5556 \
    --shm-size="2g" \
    -e SE_EVENT_BUS_HOST=<ip-from-machine-1> \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    -e SE_NODE_HOST=<ip-from-machine-4> \
    -e SE_NODE_PORT=5556 \
    selenium/node-chrome:4.26.0-20241101
Windows PowerShell
$ docker run -d -p 5556:5556 `
    --shm-size="2g" `
    -e SE_EVENT_BUS_HOST=<ip-from-machine-1> `
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 `
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 `
    -e SE_NODE_HOST=<ip-from-machine-4> `
    -e SE_NODE_PORT=5556 `
    selenium/node-chrome:4.26.0-20241101

Docker Compose

Docker Compose is the simplest way to start a Grid. Use the linked resources below, save them locally and check the execution instructions on top of each file.

Version 2

docker-compose-v2.yml

Version 3

docker-compose-v3.yml

To stop the Grid and cleanup the created containers, run docker compose down.

Version 3 with Swarm support

docker-compose-v3-swarm.yml

Fully distributed mode - Router, Queue, Distributor, EventBus, SessionMap and Nodes

It is possible to start a Selenium Grid with all its components apart. For simplicity, only an example with docker compose will be provided. Save the file locally, and check the execution instructions on top of it.

docker-compose-v3-full-grid.yml

Distributor configuration

Environment variableOptionTypeDefault valueDescription
SE_REJECT_UNSUPPORTED_CAPS--reject-unsupported-capsbooleanfalseAllow the Distributor to reject a request immediately if the Grid does not support the requested capability.
SE_HEALTHCHECK_INTERVAL--healthcheck-intervalint120This ensures the server can ping all the Nodes successfully after an interval.

Video recording

Tests execution can be recorded by using the selenium/video:ffmpeg-7.1-20241101 Docker image. One container is needed per each container where a browser is running. This means if you are running 5 Nodes/Standalone containers, you will need 5 video containers, the mapping is 1-1.

Currently, the only way to do this mapping is manually (either starting the containers manually or through docker compose). We are iterating on this process and probably this setup will be more simple in the future.

The video Docker image we provide is based on the ffmpeg Ubuntu image provided by the jrottenberg/ffmpeg project, thank you for providing this image and simplifying our work :tada:

From image tag based 4.20.0 onwards, the video Docker image is based on the FFmpeg Ubuntu image provided by linuxserver/docker-ffmpeg project since the image is available for multi-platform. Thank you for simplifying our project and helping us move forward with multiple architecture support.

Notes:

This example shows how to start the containers manually:

$ docker network create grid
$ docker run -d -p 4444:4444 -p 6900:5900 --net grid --name selenium --shm-size="2g" selenium/standalone-chrome:4.26.0-20241101
$ docker run -d --net grid --name video -v /tmp/videos:/videos selenium/video:ffmpeg-7.1-20241101
# Run your tests
$ docker stop video && docker rm video
$ docker stop selenium && docker rm selenium

After the containers are stopped and removed, you should see a video file on your machine's /tmp/videos directory.

Here is an example using a Hub and a few Nodes:

docker-compose-v3-video.yml

Video recording with dynamic file name based on metadata in tests

Based on the support of Metadata in tests. When the video recorder is sidecar deployed with the browser node with enabling SE_VIDEO_FILE_NAME=auto and adding metadata to your tests, video file name will extract value of capability se:name and use it as the video file name.

For example in Python binding:

from selenium.webdriver.chrome.options import Options as ChromeOptions
from selenium import webdriver

options = ChromeOptions()
options.set_capability('se:name', 'test_visit_basic_auth_secured_page (ChromeTests)')
driver = webdriver.Remote(options=options, command_executor="http://localhost:4444")
driver.get("https://selenium.dev")
driver.quit()

The output video file name will be test_visit_basic_auth_secured_page_ChromeTests_<sessionId>.mp4.

If your test name is handled by the test framework, and it is unique for sure, you also can disable the session id appends to the video file name by setting SE_VIDEO_FILE_NAME_SUFFIX=false.

File name will be trimmed to 255 characters to avoid long file names. Moreover, space character will be replaced by _ and only characters alphabets, numbers, - (hyphen), _ (underscore) are retained in the file name.

The trim regex is able to be customized by setting SE_VIDEO_FILE_NAME_TRIM_REGEX environment variable. The default value is [:alnum:]-_. The regex should be compatible with the tr command in bash.

At deployment level, the recorder container is up always. In addition, you can disable video recording process via session capability se:recordVideo. For example in Python binding:

options.set_capability('se:recordVideo', False)

In recorder container will perform query GraphQL in Hub based on Node SessionId and extract the value of se:recordVideo in capabilities before deciding to start video recording process or not.

Notes: To reach the GraphQL endpoint, the recorder container needs to know the Hub URL. The Hub URL can be passed via environment variable SE_NODE_GRID_URL. For example SE_NODE_GRID_URL is http://selenium-hub:4444.

Video recording and uploading

RCLONE is installed in the video recorder image. You can use it to upload the videos to a cloud storage service. Besides the video recording mentioned above, you can enable the upload functionality by setting the following environment variables:

version: "3"
services:
  chrome_video:
    image: selenium/video:ffmpeg-7.1-20241101
    depends_on:
      - chrome
    environment:
      - DISPLAY_CONTAINER_NAME=chrome
      - SE_VIDEO_FILE_NAME=auto
      - SE_VIDEO_UPLOAD_ENABLED=true
      - SE_UPLOAD_DESTINATION_PREFIX=s3://mybucket/path
      - RCLONE_CONFIG_S3_TYPE=s3
      - RCLONE_CONFIG_S3_PROVIDER=GCS
      - RCLONE_CONFIG_S3_ENV_AUTH=true
      - RCLONE_CONFIG_S3_REGION=asia-southeast1
      - RCLONE_CONFIG_S3_LOCATION_CONSTRAINT=asia-southeast1
      - RCLONE_CONFIG_S3_ACL=private
      - RCLONE_CONFIG_S3_ACCESS_KEY_ID=xxx
      - RCLONE_CONFIG_S3_SECRET_ACCESS_KEY=xxx
      - RCLONE_CONFIG_S3_ENDPOINT=https://storage.googleapis.com
      - RCLONE_CONFIG_S3_NO_CHECK_BUCKET=true

SE_VIDEO_FILE_NAME=auto will use the session id as the video file name. This ensures that the video file name is unique to upload. Video file name construction automatically works based on Node endpoint /status (and optional GraphQL endpoint) to get session ID, capabilities.

SE_VIDEO_UPLOAD_ENABLED=true will enable the video upload feature. In the background, it will create a pipefile with file and destination for uploader to consume and proceed.

SE_VIDEO_INTERNAL_UPLOAD=true will use RCLONE installed in the container for upload. If you want to use another sidecar container for upload, set it to false.

ENV variables per modeHub/NodesStandalone rolesDynamic Grid
SE_VIDEO_RECORD_STANDALONE (mandatory)false (default)truetrue
DISPLAY_CONTAINER_NAME (mandatory)user inputuser input(not required)
SE_NODE_PORT (optional)55554444(not required)
SE_NODE_GRID_URL (optional)user input(not required)(not required)

For environment variables with prefix RCLONE_ is used to pass remote configuration to RCLONE. You can find more information about RCLONE configuration here. When using in Dynamic Grid, those variables should be combined with the prefix SE_, for example SE_RCLONE_. See below reference for more details.

Reference

Environment variables and default values for upload feature

Environment variableDefault valueDescription
SE_UPLOAD_RETAIN_LOCAL_FILEfalseKeep local file after uploading successfully
SE_UPLOAD_COMMANDcopyRCLONE command is used to transfer file. Enforce move when retain local file is false
SE_UPLOAD_OPTS-P --cutoff-mode SOFT --metadata --inplaceOther options belong to RCLONE command can be set.
SE_UPLOAD_CONFIG_FILE_NAMEupload.confConfig file for remote host instead of set via env variable prefix SE_RCLONE_*
SE_UPLOAD_CONFIG_DIRECTORY/opt/binDirectory of config file (change it when conf file in another directory is mounted)

Dynamic Grid

Grid 4 has the ability to start Docker containers on demand, this means that it starts a Docker container in the background for each new session request, the test gets executed there, and when the test completes, the container gets thrown away.

This execution mode can be used either in the Standalone or Node roles. The "dynamic" execution mode needs to be told what Docker images to use when the containers get started. Additionally, the Grid needs to know the URI of the Docker daemon. This configuration can be placed in a local toml file.

Configuration example

You can save this file locally and name it, for example, config.toml.

[docker]
# Configs have a mapping between the Docker image to use and the capabilities that need to be matched to
# start a container with the given image.
configs = [
    "selenium/standalone-firefox:4.26.0-20241101", '{"browserName": "firefox"}',
    "selenium/standalone-chrome:4.26.0-20241101", '{"browserName": "chrome"}',
    "selenium/standalone-edge:4.26.0-20241101", '{"browserName": "MicrosoftEdge"}'
]

host-config-keys = ["Dns", "DnsOptions", "DnsSearch", "ExtraHosts", "Binds"]

# URL for connecting to the docker daemon
# Most simple approach, leave it as http://127.0.0.1:2375, and mount /var/run/docker.sock.
# 127.0.0.1 is used because internally the container uses socat when /var/run/docker.sock is mounted 
# If var/run/docker.sock is not mounted: 
# Windows: make sure Docker Desktop exposes the daemon via tcp, and use http://host.docker.internal:2375.
# macOS: install socat and run the following command, socat -4 TCP-LISTEN:2375,fork UNIX-CONNECT:/var/run/docker.sock,
# then use http://host.docker.internal:2375.
# Linux: varies from machine to machine, please mount /var/run/docker.sock. If this does not work, please create an issue.
url = "http://127.0.0.1:2375"
# Docker image used for video recording
video-image = "selenium/video:ffmpeg-7.1-20241101"

# Uncomment the following section if you are running the node on a separate VM
# Fill out the placeholders with appropriate values
#[server]
#host = <ip-from-node-machine>
#port = <port-from-node-machine>

With the optional config key host-config-keys under section [docker] in a config.toml file (or CLI option --docker-host-config-keys). Users can specify a list of docker host configuration keys that should be passed to browser containers.

Valid key names for Docker host config can be found in the Docker API documentation or via the command docker inspect the node-docker container.

Share volumes config of Dynamic Grid container to node browser containers

In case you want to access download directory in node browser containers (e.g /home/seluser/Downloads) via volumes config of Dynamic Grid container, you can add the following config to the config.toml file

[docker]
host-config-keys = ["Binds"]

Volumes config in docker compose file

services:
  node-docker:
    image: selenium/node-docker:latest
    volumes:
      - ./assets:/opt/selenium/assets
      - ./config.toml:/opt/selenium/docker.toml
      - ./downloads:/home/seluser/Downloads
      - /var/run/docker.sock:/var/run/docker.sock
    environment:
      - SE_NODE_DOCKER_CONFIG_FILENAME=docker.toml

/opt/selenium/config.toml is the default path for the config file in all images. Once volumes config is shared to node browser containers, its config.toml could be overwritten by node-docker container config file.

In this case, mount your config.toml file to /opt/selenium/docker.toml in node-docker container. And set the environment variable SE_NODE_DOCKER_CONFIG_FILENAME=docker.toml to specify that config file name for the startup script.

Refer to example docker-compose-v3-test-node-docker.yaml

Execution with Hub & Node roles

This can be expanded to a full Grid deployment, all components deployed individually. The overall idea is to have the Hub in one virtual machine, and each of the Nodes in separate and more powerful virtual machines.

macOS/Linux

$ docker network create grid
$ docker run -d -p 4442-4444:4442-4444 --net grid --name selenium-hub selenium/hub:4.26.0-20241101
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    -v ${PWD}/config.toml:/opt/selenium/config.toml \
    -v ${PWD}/assets:/opt/selenium/assets \
    -v /var/run/docker.sock:/var/run/docker.sock \
    selenium/node-docker:4.26.0-20241101

Windows PowerShell

$ docker network create grid
$ docker run -d -p 4442-4444:4442-4444 --net grid --name selenium-hub selenium/hub:4.26.0-20241101
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub `
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 `
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 `
    -v ${PWD}/config.toml:/opt/selenium/config.toml `
    -v ${PWD}/assets:/opt/selenium/assets `
    -v /var/run/docker.sock:/var/run/docker.sock `
    selenium/node-docker:4.26.0-20241101

To have the assets saved on your host, please mount your host path to /opt/selenium/assets.

When you are done using the Grid, and the containers have exited, the network can be removed with the following command:

# Removes the grid network
$ docker network rm grid

Execution with Standalone roles

macOS/Linux

docker run --rm --name selenium-docker -p 4444:4444 \
    -v ${PWD}/config.toml:/opt/selenium/config.toml \
    -v ${PWD}/assets:/opt/selenium/assets \
    -v /var/run/docker.sock:/var/run/docker.sock \
    selenium/standalone-docker:4.26.0-20241101

Windows PowerShell

docker run --rm --name selenium-docker -p 4444:4444 `
    -v ${PWD}/config.toml:/opt/selenium/config.toml `
    -v ${PWD}/assets:/opt/selenium/assets `
    -v /var/run/docker.sock:/var/run/docker.sock `
    selenium/standalone-docker:4.26.0-20241101

Using Dynamic Grid in different machines/VMs

Hub - Machine/VM 1

$ docker run -d -p 4442-4444:4442-4444 --name selenium-hub selenium/hub:4.26.0-20241101

Node Chrome - Machine/VM 2

macOS/Linux

$ docker run -d -p 5555:5555 \
    -e SE_EVENT_BUS_HOST=<ip-from-machine-1> \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    -v ${PWD}/config.toml:/opt/selenium/config.toml \
    -v ${PWD}/assets:/opt/selenium/assets \
    -v /var/run/docker.sock:/var/run/docker.sock \
    selenium/node-docker:4.26.0-20241101

Windows PowerShell

$ docker run -d -p 5555:5555 `
    -e SE_EVENT_BUS_HOST=<ip-from-machine-1> `
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 `
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 `
    -v ${PWD}/config.toml:/opt/selenium/config.toml `
    -v ${PWD}/assets:/opt/selenium/assets `
    -v /var/run/docker.sock:/var/run/docker.sock `
    selenium/node-docker:4.26.0-20241101

Complete the [server] section in the config.toml file.

[docker]
# Configs have a mapping between the Docker image to use and the capabilities that need to be matched to
# start a container with the given image.
configs = [
    "selenium/standalone-firefox:4.26.0-20241101", "{\"browserName\": \"firefox\"}",
    "selenium/standalone-chrome:4.26.0-20241101", "{\"browserName\": \"chrome\"}",
    "selenium/standalone-edge:4.26.0-20241101", "{\"browserName\": \"MicrosoftEdge\"}"
    ]

# URL for connecting to the docker daemon
# Most simple approach, leave it as http://127.0.0.1:2375, and mount /var/run/docker.sock.
# 127.0.0.1 is used because interally the container uses socat when /var/run/docker.sock is mounted 
# If var/run/docker.sock is not mounted: 
# Windows: make sure Docker Desktop exposes the daemon via tcp, and use http://host.docker.internal:2375.
# macOS: install socat and run the following command, socat -4 TCP-LISTEN:2375,fork UNIX-CONNECT:/var/run/docker.sock,
# then use http://host.docker.internal:2375.
# Linux: varies from machine to machine, please mount /var/run/docker.sock. If this does not work, please create an issue.
url = "http://127.0.0.1:2375"
# Docker image used for video recording
video-image = "selenium/video:ffmpeg-7.1-20241101"

# Uncomment the following section if you are running the node on a separate VM
# Fill out the placeholders with appropriate values
[server]
host = <ip-from-node-machine>
port = <port-from-node-machine>

To have the assets saved on your host, please mount your host path to /opt/selenium/assets.

Execution with Docker Compose

Here is an example using a Hub and a Node:

docker-compose-v3-dynamic-grid.yml

Configuring the child containers

Containers can be further configured through environment variables, such as SE_NODE_SESSION_TIMEOUT and SE_OPTS. When a child container is created, all environment variables prefixed with SE_ will be forwared and set in the container. You can set the desired environment variables in the standalone-docker or node-docker containers. The following example sets the session timeout to 700 seconds for all sessions:

macOS/Linux

docker run --rm --name selenium-docker -p 4444:4444 \
    -e SE_NODE_SESSION_TIMEOUT=700 \
    -v ${PWD}/config.toml:/opt/selenium/config.toml \
    -v ${PWD}/assets:/opt/selenium/assets \
    -v /var/run/docker.sock:/var/run/docker.sock \
    selenium/standalone-docker:4.26.0-20241101

Windows PowerShell

docker run --rm --name selenium-docker -p 4444:4444 `
    -e SE_NODE_SESSION_TIMEOUT=700 `
    -v ${PWD}/config.toml:/opt/selenium/config.toml `
    -v ${PWD}/assets:/opt/selenium/assets `
    -v /var/run/docker.sock:/var/run/docker.sock `
    selenium/standalone-docker:4.26.0-20241101

Video recording, screen resolution, and time zones in a Dynamic Grid

To record your WebDriver session, you need to add a se:recordVideo field set to true. You can also set a time zone and a screen resolution, for example:

{
  "browserName": "firefox",
  "platformName": "linux",
  "se:recordVideo": "true",
  "se:timeZone": "US/Pacific",
  "se:screenResolution": "1920x1080"  
}

After running a test, check the path you mounted to the Docker container, (${PWD}/assets), and you should see videos and session information.

From language bindings, you can set the se:name capability to change output video file name dynamically. For example, in Python binding:

from selenium.webdriver.chrome.options import Options as ChromeOptions
from selenium import webdriver

options = ChromeOptions()
options.set_capability('se:recordVideo', True)
options.set_capability('se:screenResolution', '1920x1080')
options.set_capability('se:name', 'test_visit_basic_auth_secured_page (ChromeTests)')
driver = webdriver.Remote(options=options, command_executor="http://localhost:4444")
driver.get("https://selenium.dev")
driver.quit()

After test executed, under (${PWD}/assets) you can see the video file name in path /<sessionId>/test_visit_basic_auth_secured_page_ChromeTests.mp4

The file name will be trimmed to 255 characters to avoid long file names. Moreover, the space character will be replaced by _, and only the characters alphabets, numbers, - (hyphen), and _ (underscore) are retained in the file name. (This feat is available once this PR merged)

Time zone configuration via env variable

tzdata is installed in based images, and you can set the time zone in container by using the env variable TZ. By default, the time zone is set to UTC. List of supported time zones can be found here. For example:

$ docker run --rm --entrypoint="" -e TZ=Asia/Ho_Chi_Minh selenium/node-chromium:latest date +%FT%T%Z
2024-08-28T18:19:26+07

Deploying to Kubernetes

We offer a Helm chart to deploy these Docker images to Kubernetes. Read more details at the Helm readme.

Configuring the containers

SE_OPTS Selenium Configuration Options

You can pass SE_OPTS variable with additional command line parameters for starting a hub or a node.

$ docker run -d -p 4444:4444 -e SE_OPTS="--log-level FINE" --name selenium-hub selenium/hub:4.26.0-20241101

SE_JAVA_OPTS Java Environment Options

You can pass SE_JAVA_OPTS environment variable to the Java process.

$ docker run -d -p 4444:4444 -e SE_JAVA_OPTS=-Xmx512m --name selenium-hub selenium/hub:4.26.0-20241101

SE_BROWSER_ARGS_* Add arguments for launching browser

Instead of adding arguments via the browser options from language bindings, for example:

options = ChromeOptions()
options.add_argument('--incognito')
options.add_argument('--disable-dev-shm-usage')
driver = webdriver.Remote(options=options, command_executor="http://localhost:4444/wd/hub")

You also can proactive to force applying arguments directly from (node, standalone or node-docker) container environment variables. Define the environment variable with name starts with SE_BROWSER_ARGS_ and following by config key is up to you (ensure those are unique when you define multiple arguments). For example:

docker run -d -p 4444:4444 \
  -e SE_BROWSER_ARGS_INCOGNITO=--incognito \
  -e SE_BROWSER_ARGS_DISABLE_DSHM=--disable-dev-shm-usage \
  selenium/standalone-chrome:latest

List chromium command-line arguments for your reference.

Note: Currently, this is applicable for node browsers Chrome/Chromium, Edge.

Node configuration options

The Nodes register themselves through the Event Bus. When the Grid is started in its typical Hub/Node setup, the Hub will be the one acting as the Event Bus, and when the Grid is started with all its five elements apart, the Event Bus will be running on its own.

In both cases, it is necessary to tell the Node where the Event Bus is, so it can register itself. That is the purpose of the SE_EVENT_BUS_HOST, SE_EVENT_BUS_PUBLISH_PORT and SE_EVENT_BUS_SUBSCRIBE_PORT environment variables.

In some cases, for example, if you want to tag a node, it might be necessary to supply a custom stereotype to the node config. The environment variable SE_NODE_STEREOTYPE sets the stereotype entry in the node's config.toml. An example config.toml file can be found here: Setting custom capabilities for matching specific Nodes.

Here is an example with the default values of these environment variables:

$ docker run -d \
  -e SE_EVENT_BUS_HOST=<event_bus_ip|event_bus_name> \
  -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
  -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 -e SE_NODE_STEREOTYPE="{\"browserName\":\"${SE_NODE_BROWSER_NAME}\",\"browserVersion\":\"${SE_NODE_BROWSER_VERSION}\",\"platformName\": \"Linux\"}" \
  --shm-size="2g" selenium/node-chrome:4.26.0-20241101

Node configuration relay commands

Relaying commands to a service endpoint that supports WebDriver. It is useful to connect an external service that supports WebDriver to Selenium Grid. An example of such service could be a cloud provider or an Appium server. In this way, Grid can enable more coverage to platforms and versions not present locally.

The following is an en example of configuration relay commands.

docker-compose-v3-test-node-relay.yml

If you want to relay commands only, selenium/node-base is suitable and lightweight for this purpose. In case you want to configure node with both browsers and relay commands, respective node images can be used.

To use environment variables for generate relay configs, set SE_NODE_RELAY_URL and other variables as below

[relay]
url = "${SE_NODE_RELAY_URL}"
status-endpoint = "${SE_NODE_RELAY_STATUS_ENDPOINT}"
protocol-version = "${SE_NODE_RELAY_PROTOCOL_VERSION}"
configs = [ '${SE_NODE_RELAY_MAX_SESSIONS}', '{"browserName": "${SE_NODE_RELAY_BROWSER_NAME}", "platformName": "${SE_NODE_RELAY_PLATFORM_NAME}", "appium:platformVersion": "${SE_NODE_RELAY_PLATFORM_VERSION}"}' ]

To run a sample test with the relayed node, you can clone the project and try below command:

make test_node_relay

Setting Sub Path

By default, Selenium is reachable at http://127.0.0.1:4444/. Selenium can be configured to use a custom subpath by specifying the SE_SUB_PATH environmental variable. In the example below Selenium is reachable at http://127.0.0.1:4444/selenium-grid/

$ docker run -d -p 4444:4444 -e SE_SUB_PATH=/selenium-grid/ --name selenium-hub selenium/hub:4.26.0-20241101

Setting Screen Resolution

By default, nodes start with a screen resolution of 1920 x 1080 with a color depth of 24 bits and a dpi of 96. These settings can be adjusted by specifying SE_SCREEN_WIDTH, SE_SCREEN_HEIGHT, SE_SCREEN_DEPTH, and/or SE_SCREEN_DPI environmental variables when starting the container.

docker run -d -e SE_SCREEN_WIDTH=1366 -e SE_SCREEN_HEIGHT=768 -e SE_SCREEN_DEPTH=24 -e SE_SCREEN_DPI=74 selenium/standalone-firefox:4.26.0-20241101

Grid Url and Session Timeout

In some use cases, you might need to set the Grid URL to the Node, for example, if you'd like to access the BiDi/CDP endpoint. This is also needed when you want to use the new RemoteWebDriver.builder() or Augmenter() present in Selenium 4 (since they setup the BiDi/CDP connection implicitly). You can do that through the SE_NODE_GRID_URL environment variable, eg -e SE_NODE_GRID_URL=http://<hostMachine>:4444. Setting this env var is needed if you want to see the live view while sessions are executing.

Grid has a default session timeout of 300 seconds, where the session can be in a stale state until it is killed. You can use SE_NODE_SESSION_TIMEOUT to overwrite that value in seconds.

Session request timeout

A new session request is placed in the Session Queue before it is processed, and the request sits in the queue until a matching slot is found across the registered Nodes. However, the new session request might timeout if no slot was found. By default, a request will stay in the queue for up to 300 seconds before it a timeout is reached. In addition, an attempt to process the request is done every 5 seconds (by default).

It is possible to override those values through environment variables in the Hub and the SessionQueue (SE_SESSION_REQUEST_TIMEOUT and SE_SESSION_RETRY_INTERVAL). For example, a timeout of 500 seconds would be SE_SESSION_REQUEST_TIMEOUT=500 and a retry interval of 2 seconds would be SE_SESSION_RETRY_INTERVAL=2.

Increasing session concurrency per container

By default, only one session is configured to run per container through the SE_NODE_MAX_SESSIONS environment variable. It is possible to increase that number up to the maximum available processors, this is because more stability is achieved when one container/browser has 1 CPU to run.

However, if you have measured performance and based on that, you think more sessions can be executed in each container, you can override the maximum limit by setting both SE_NODE_MAX_SESSIONS to a desired number and SE_NODE_OVERRIDE_MAX_SESSIONS to true. Nevertheless, running more browser sessions than the available processors is not recommended since you will be overloading the resources.

Overriding this setting has an undesired side effect when video recording is enabled since more than one browser session might be captured in the same video.

Running in Headless mode

Firefox, Chrome, When using headless mode, there's no need for the Xvfb server to be started.

To avoid starting the server you can set the SE_START_XVFB environment variable to false (or any other value than true), for example:

$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
  -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 -e SE_START_XVFB=false --shm-size="2g" selenium/node-chrome:4.26.0-20241101

For more information, see this GitHub issue.

Noted:

Stopping the Node/Standalone after N sessions have been executed

In some environments, like Docker Swarm or Kubernetes, it is useful to shut down the Node or Standalone container after N tests have been executed. For example, this can be used in Kubernetes to terminate the pod and then scale a new one after N sessions. Set the environment variable SE_DRAIN_AFTER_SESSION_COUNT to a value higher than zero to enable this behaviour.

$ docker run -e SE_DRAIN_AFTER_SESSION_COUNT=5 --shm-size="2g" selenium/standalone-firefox:4.26.0-20241101

With the previous command, the Standalone container will shut down after 5 sessions have been executed.

Automatic browser leftovers cleanup

In long-running containers, it can happen that browsers leave some leftovers. These can be stuck browser processes of jobs that have already finished but failed to fully stop the browser, or temporary files written to the /tmp file system (notably on Chrome-based browsers). To avoid these filling up resources like process IDs and file system usage in the container, there is an automatic cleanup script running every hour in the node containers. This will clean up old processes and old temporary files. By default, this is disabled. When enabled, this will clean up browsers running for longer than 2 hours, and files older than 1 day. These can be enabled and tweaked with the following environment variables:

If you use Selenium for long-running sessions and expect browsers to be running for longer than 2 hours, either do not set SE_ENABLE_BROWSER_LEFTOVERS_CLEANUP to true (leave the default value of false), or tweak SE_BROWSER_LEFTOVERS_PROCESSES_SECS to set a value higher than your expected long-running browser processes.

$ docker run -e SE_ENABLE_BROWSER_LEFTOVERS_CLEANUP=true --shm-size="2g" selenium/node-chrome:4.26.0-20241101

With the previous command, the cleanup will be enabled with the default timings.

$ docker run -e SE_ENABLE_BROWSER_LEFTOVERS_CLEANUP=true \
-e SE_BROWSER_LEFTOVERS_INTERVAL_SECS=7200 \
-e SE_BROWSER_LEFTOVERS_PROCESSES_SECS=3600 \
-e SE_BROWSER_LEFTOVERS_TEMPFILES_DAYS=2 \
--shm-size="2g" selenium/node-chrome:4.26.0-20241101

With the previous command, the cleanup will be enabled, but will run every 2 hours (instead of 1), will kill browsers running longer than 1 hour (instead of 2 hours), and will remove temp files older than 2 days (instead of 1).

Mask sensitive information in console logs

Few variables output like password, secret, etc. are masked in console logs. For debugging purposes, you can disable it by setting SE_MASK_SECRETS to false

While creating bash script, your can mask the output by using syntax echo "Current value is $(mask ${YOUR_VARIABLE})

SE_MASK_SECRETS_MIN_LENGTH default is 3. It means a long string will be masked to *** to avoid exposing length for brute force attack.

Secure connection

By default, there are default self-signed certificates available in the image in location /opt/selenium/secrets includes

There are environment variables to configure the secure connection:

Environment variablesDefaultOption ofDescription
SE_ENABLE_TLSfalseEnable secure connection with default configs
SE_JAVA_SSL_TRUST_STORE/opt/selenium/secrets/server.jksJVM
SE_JAVA_SSL_TRUST_STORE_PASSWORD/opt/selenium/secrets/server.passJVM
SE_JAVA_DISABLE_HOSTNAME_VERIFICATIONtrueJVMDisable host checks for components internally
SE_HTTPS_CERTIFICATE/opt/selenium/secrets/tls.crtSeleniumSet to CLI option --https-certificate
SE_HTTPS_PRIVATE_KEY/opt/selenium/secrets/tls.keySeleniumSet to CLI option --https-private-key

Via volume mount, you can replace the default certificates with your own certificates.

The self-signed certificate also needs to be trusted by the client (add to system widely bundle trusted CA) to avoid error message relates to SSL handshake when creating RemoteWebDriver.

Refer to sample: docker-compose-v3-full-grid-secure.yml

Browser language and locale

Different browsers have different ways to set the language and locale from binding.

Firefox

Firefox can be configured to use a specific language and locale by setting the profile preference when create WebDriver from binding. In addition, language pack need to be installed as add-on for browser UI language to take effect. For example, to set the browser language and locale to vi-VN, you can use the following steps:

Get the latest Firefox language pack for the desired language e.g. https://download.mozilla.org/?product=firefox-langpack-latest-SSL&lang=vi. Then, you can install the language pack as an add-on when creating the RemoteWebDriver instance.

profile = webdriver.FirefoxProfile()
profile.set_preference('intl.accept_languages', 'vi-VN,vi')
profile.set_preference('intl.locale.requested', 'vi-VN,vi')
options = FirefoxOptions()
options.profile = profile
driver = webdriver.Remote(options=options, command_executor="http://selenium-hub:4444/wd/hub")
webdriver.Firefox.install_addon(driver, "/local/path/to/vi.xpi")
driver.get('https://google.com')

There is a script to get all available language packs for a given Firefox version. You can run the script to get the language packs to your source. For example:

FIREFOX_VERSION=$(docker run --rm --entrypoint="" selenium/node-firefox:latest firefox --version | awk '{print $3}') \
&& ./NodeFirefox/get_lang_package.sh ${FIREFOX_VERSION} /local/path/to/download

Or, you can mount the container directory /home/seluser/firefox/distribution/extensions to host directory to access packs were pre-built in the container for using in your test script.

Managing processes in container

Supervisor is used to manage processes and logs in the container. Few configuration for supervisord can be set via environment variables as below:

Environment variablesDefaultsupervisord config
SE_SUPERVISORD_LOG_LEVELinfosupervisord.loglevel
SE_SUPERVISORD_CHILD_LOG_DIR/tmpsupervisord.childlogdir
SE_SUPERVISORD_LOG_FILE/tmp/supervisord.logsupervisord.logfile
SE_SUPERVISORD_PID_FILE/tmp/supervisord.pidsupervisord.pidfile

Building the images

Clone the repo and from the project directory root you can build everything by running:

$ VERSION=local make build

If you need to configure environment variables in order to build the image (http proxy for instance), simply set an environment variable BUILD_ARGS that contains the additional variables to pass to the docker context (this will only work with docker >= 1.9)

$ BUILD_ARGS="--build-arg http_proxy=http://acme:3128 --build-arg https_proxy=http://acme:3128" make build

Note: Omitting VERSION=local will build the images with the released version but replacing the date for the current one.

If you want to build the image with the host UID/GID, simply set an environment variable BUILD_ARGS

$ BUILD_ARGS="--build-arg UID=$(id -u) --build-arg GID=$(id -g)" make build

If you want to build the image with different default user/password, simply set an environment variable BUILD_ARGS

$ BUILD_ARGS="--build-arg SEL_USER=yourseluser --build-arg SEL_PASSWD=welcome" make build

Build the images with specific versions

Based on the latest Dockerfile (by cloning the repo and from the project directory root), you can build the images with a specific combination of Selenium Grid, and browser versions.

For example, you would like to build node-chrome and standalone-chrome images with the Grid based version 4.17.0, Chrome browser versions 119, 120, 123 respectively.

$ ./tests/build-backward-compatible/bootstrap.sh 4.17.0 119,120,123 chrome

In generic, the script takes the following arguments:

To set your namespace for the images, you can set the environment variable NAME before running the script. For example:

$ export NAME=artifactory.yourcompany.com/selenium
$ ./tests/build-backward-compatible/bootstrap.sh 4.17.0 119,120,123 chrome

After running the script, you will see list images with a full tag to pin specific Grid and browser version following Tagging Conventions

Upgrade browser version in the images

Selenium server, browser and driver are pre-installed in the image. In case you would like to remain on the same Selenium version and just upgrade the browser and its driver to the latest. You can follow below steps

Clone the repo and from the project directory root you can upgrade by running:

$ VERSION=$EXPECTED_SELENIUM_VERSION make chrome_upgrade_version

For example: VERSION=4.16.1 make chrome_upgrade_version

The new image has tag $VERSION_YYYYMMDD where YYYYMMDD is the current date.

$ VERSION=$SELENIUM_VERSION make firefox_upgrade_version

$ VERSION=$SELENIUM_VERSION make edge_upgrade_version

You can refer to detail commands in the Makefile file.

Waiting for the Grid to be ready

It is a good practice to check first if the Grid is up and ready to receive requests, this can be done by checking the /wd/hub/status endpoint.

A Grid that is ready, composed of a hub and two nodes, could look like this:

{
  "value": {
    "ready": true,
    "message": "Selenium Grid ready.",
    "nodes": [
      {
        "id": "6c0a2c59-7e99-469d-bbfc-313dc638797c",
        "uri": "http:\u002f\u002f172.19.0.3:5555",
        "maxSessions": 4,
        "stereotypes": [
          {
            "capabilities": {
              "browserName": "firefox"
            },
            "count": 4
          }
        ],
        "sessions": [
        ]
      },
      {
        "id": "26af3363-a0d8-4bd6-a854-2c7497ed64a4",
        "uri": "http:\u002f\u002f172.19.0.4:5555",
        "maxSessions": 4,
        "stereotypes": [
          {
            "capabilities": {
              "browserName": "chrome"
            },
            "count": 4
          }
        ],
        "sessions": [
        ]
      }
    ]
  }
}

The "ready": true value indicates that the Grid is ready to receive requests. This status can be polled through a script before running any test, or it can be added as a HEALTHCHECK when the docker container is started.

Adding a HEALTHCHECK to the Grid

The script check-grid.sh, which is included in the images, can be used to poll the Grid status.

This example checks the status of the Grid every 15 seconds, it has a timeout of 30 seconds when the check is done, and it retries up to 5 times until the container is marked as unhealthy. Please use adjusted values to fit your needs, (if needed) replace the --host and --port parameters for the ones used in your environment.

$ docker network create grid
$ docker run -d -p 4442-4444:4442-4444 --net grid --name selenium-hub \
  --health-cmd='/opt/bin/check-grid.sh --host 0.0.0.0 --port 4444' \
  --health-interval=15s --health-timeout=30s --health-retries=5 \
  selenium/hub:4.26.0-20241101
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub \
    --shm-size="2g" \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    selenium/node-chrome:4.26.0-20241101
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub \
    --shm-size="2g" \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    selenium/node-edge:4.26.0-20241101
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub \
    --shm-size="2g" \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    selenium/node-firefox:4.26.0-20241101

Note: The \ line delimiter won't work on Windows-based terminals, try either ^ or a backtick.

The container health status can be checked by doing docker ps and verifying the (healthy)|(unhealthy) status or by inspecting it in the following way:

$ docker inspect --format='{{json .State.Health.Status}}' selenium-hub
"healthy"

Using a bash script to wait for the Grid

A common problem known in docker is that a running container does not always mean that the application inside it is ready. A simple way to tackle this is by using a "wait-for-it" script, more information can be seen here.

The following script is an example of how this can be done using bash, but the same principle applies if you want to do this with the programming language used to write the tests. In the example below, the script will poll the status endpoint every second. If the grid does not become ready within 30 seconds, the script will exit with an error code.

#!/bin/bash
# wait-for-grid.sh

set -e
url="http://localhost:4444/wd/hub/status"
wait_interval_in_seconds=1
max_wait_time_in_seconds=30
end_time=$((SECONDS + max_wait_time_in_seconds))
time_left=$max_wait_time_in_seconds

while [ $SECONDS -lt $end_time ]; do
    response=$(curl -sL "$url" | jq -r '.value.ready')
    if [ -n "$response"  ]  && [ "$response" ]; then
        echo "Selenium Grid is up - executing tests"
        break
    else
        echo "Waiting for the Grid. Sleeping for $wait_interval_in_seconds second(s). $time_left seconds left until timeout."
        sleep $wait_interval_in_seconds
        time_left=$((time_left - wait_interval_in_seconds))
    fi
done

if [ $SECONDS -ge $end_time ]; then
    echo "Timeout: The Grid was not started within $max_wait_time_in_seconds seconds."
    exit 1
fi

Will require jq installed via apt-get, else the script will keep printing Waiting without completing the execution.

Note: If needed, replace localhost and 4444 for the correct values in your environment. Also, this script is polling indefinitely, you might want to tweak it and establish a timeout.

Let's say that the normal command to execute your tests is mvn clean test. Here is a way to use the above script and execute your tests:

$ ./wait-for-grid.sh && mvn clean test

Like this, the script will poll until the Grid is ready, and then your tests will start.

Install certificates for Chromium-based browsers

By default, the based image is installed libnss3-tools and initializes /home/seluser/.pki/nssdb, so you are able to add your certs with rootless. If you need to install custom certificates, CA, intermediate CA, or client certificates (for example, enterprise internal CA) you can create your own docker image from selenium node image. The Chromium-based browser uses nssdb as a certificate store. You can then install all required internal certificates in your Dockerfile like this:

There is a utility script packaged in the image that can be used to add your certificates to the nssdb store and the bundle CA. The script is /opt/bin/add-cert-helper.sh.

The above example can be tested with the following command:

make test_custom_ca_cert
# ./tests/customCACert/bootstrap.sh

You can find more information here

This way the certificates will be installed and the node will start automatically as before.

Alternative method: Add certificates to existing Selenium based images for browsers

As an alternative, you can add your certificate files to existing Selenium images. This practical example assumes you have a known image to use as a build image and have a way to publish new images to your local docker registry.

This example uses a RedHat-based distro as a build image (Rocky Linux) but it can be any Linux image of your choice. Please note that build instruction will vary between distributions. You can check the instructions for Ubuntu in the previous example.

The example also assumes your internal CA is already in /etc/pki/ca-trust/source/anchors/YOUR_CA.pem, the default location for Rocky Linux. Alternatively, you can also provide these files from your host and copy them into the build image.

For Chrome and Edge browsers, the recipe is the same, just adapt the image name (node-chrome or node-edge):

# Get a standard image for creating nssdb file
FROM rockylinux:8.6 as build
RUN yum install -y nss-tools
RUN mkdir -p -m755 /seluser/.pki/nssdb \
    && certutil -d sql:/seluser/.pki/nssdb -N --empty-password \
    && certutil -d sql:/seluser/.pki/nssdb -A -t "C,," -n YOUR_CA -i /etc/pki/ca-trust/source/anchors/YOUR_CA.pem \
    && chown -R 1200:1201 /seluser

# Start from Selenium image and add relevant files from build image
FROM selenium/node-chrome:4.26.0-20241101
USER root
COPY --from=build /seluser/ /home/seluser/
USER seluser

Example for Firefox:

# Get a standard image for working on
FROM rockylinux:8.6 as build
RUN mkdir -p "/distribution" "/certs" && \
    cp /etc/pki/ca-trust/source/anchors/YOUR_CA*.pem /certs/ && \
    echo '{ "policies": { "Certificates": { "Install": ["/opt/firefox-latest/YOUR_CA.pem"] }} }' >"/distribution/policies.json"

# Start from Selenium image and add relevant files from build image
FROM selenium/node-firefox:4.26.0-20241101
USER root
COPY --from=build /certs /opt/firefox-latest
COPY --from=build /distribution /opt/firefox-latest/distribution
USER seluser

Debugging

This project uses x11vnc as a VNC server to allow users to inspect what is happening inside the container. Users can connect to this server in two ways:

Using a VNC client

The VNC server is listening to port 5900, you can use a VNC client and connect to it. Feel free to map port 5900 to any free external port that you wish.

The internal 5900 port remains the same because that is the configured port for the VNC server running inside the container. You can override it with the SE_VNC_PORT environment variable in case you want to use --net=host.

Here is an example with the standalone images, the same concept applies to the node images.

$ docker run -d -p 4444:4444 -p 5900:5900 --shm-size="2g" selenium/standalone-chrome:4.26.0-20241101
$ docker run -d -p 4445:4444 -p 5901:5900 --shm-size="2g" selenium/standalone-edge:4.26.0-20241101
$ docker run -d -p 4446:4444 -p 5902:5900 --shm-size="2g" selenium/standalone-firefox:4.26.0-20241101

Then, you would use in your VNC client:

If you get a prompt asking for a password, it is: secret. If you wish to change this, you can set the environment variable SE_VNC_PASSWORD.

If you want to run VNC without password authentication you can set the environment variable SE_VNC_NO_PASSWORD=1.

If you want to run VNC in view-only mode you can set the environment variable SE_VNC_VIEW_ONLY=1.

If you want to modify the open file descriptor limit for the VNC server process you can set the environment variable SE_VNC_ULIMIT=4096.

Using your browser (no VNC client is needed)

This project uses noVNC to allow users to inspect visually container activity with their browser. This might come in handy if you cannot install a VNC client on your machine. Port 7900 is used to start noVNC, so you will need to connect to that port with your browser.

Similarly to the previous section, feel free to map port 7900 to any free external port that you wish. You can also override it with the SE_NO_VNC_PORT environment variable in case you want to use --net=host.

Here is an example with the standalone images, the same concept applies to the node images.

$ docker run -d -p 4444:4444 -p 7900:7900 --shm-size="2g" selenium/standalone-chrome:4.26.0-20241101
$ docker run -d -p 4445:4444 -p 7901:7900 --shm-size="2g" selenium/standalone-edge:4.26.0-20241101
$ docker run -d -p 4446:4444 -p 7902:7900 --shm-size="2g" selenium/standalone-firefox:4.26.0-20241101

Then, you would use in your browser:

If you get a prompt asking for a password, it is: secret.

Disabling VNC

If You are running low on resources, or simply don't need to inspect running sessions, it is possible to not run VNC at all. Just set SE_START_VNC=false environment variable on the grid startup.

Tracing in Grid

In order to enable tracing in the Selenium Grid container, the following commands can be executed:

docker network create grid
docker run -d -p 16686:16686 -p 4317:4317 --net grid --name jaeger jaegertracing/all-in-one:1.54
docker run -d -p 4442-4444:4442-4444 --net grid --name selenium-hub selenium/hub:4.26.0-20241101
docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub \
    --shm-size="2g" \
	-e SE_ENABLE_TRACING=true \
	-e SE_OTEL_TRACES_EXPORTER=otlp \
	-e SE_OTEL_EXPORTER_ENDPOINT=http://jaeger:4317 \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    selenium/node-chrome:4.26.0-20241101
docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub \
    --shm-size="2g" \
	-e SE_ENABLE_TRACING=true \
	-e SE_OTEL_TRACES_EXPORTER=otlp \
	-e SE_OTEL_EXPORTER_ENDPOINT=http://jaeger:4317 \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    selenium/node-edge:4.26.0-20241101
docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub \
    --shm-size="2g" \
	-e SE_ENABLE_TRACING=true \
	-e SE_OTEL_TRACES_EXPORTER=otlp \
	-e SE_OTEL_EXPORTER_ENDPOINT=http://jaeger:4317 \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    selenium/node-firefox:4.26.0-20241101

You can also refer to the below docker compose yaml files to be able to start a simple grid (or) a dynamic grid.

You can view the Jaeger UI and trace your request.

By default, the tracing is enabled in Grid components. Without trace exporter endpoint, it will look up a local instance e.g. localhost/[0:0:0:0:0:0:0:1]:4117. In container logs you can see few lines like below:

ERROR (ThrottlingLogger.dolog) Failed to export spans.
  The request could not be executed. Error message: Failed to connect to localhost/[0:0:0:0:0:0:0:1]:4117
  java.net.ConnectException: Failed to connect to localhost/[0:0:0:0:0:0:0:1]:4317 
at okhttp3.internal.connection.RealConnection.connectSocket(RealConnection.kt:297)
at okhttp3.internal.connection. ExchangeFinder.findConnection (Exchangefinder.kt: 226)
at okhttp3.internal.connection.okhttps.internal.connection.RealConnection.connect(RealConnection.kt:207)

In this case, just simply set SE_ENABLE_TRACING=false to all components container to disable tracing (each component exports its own traces).

Troubleshooting

All output gets sent to stdout, so it can be inspected by running:

$ docker logs -f <container-id|container-name>

You can increase the log output by passing environment variable to the containers:

SE_OPTS="--log-level FINE"

--shm-size="2g"

Why is --shm-size 2g necessary?

This is a known workaround to avoid the browser crashing inside a docker container, here are the documented issues for Chrome and Firefox. The shm size of 2gb is arbitrary but known to work well, your specific use case might need a different value, it is recommended to tune this value according to your needs.

Headless

If you see the following selenium exceptions:

Message: invalid argument: can't kill an exited process

or

Message: unknown error: Chrome failed to start: exited abnormally

or

[DriverServiceSessionFactory.apply] - Error while creating session with the driver service. Stopping driver service: java.util.concurrent.TimeoutException

The reason might be that you've set the SE_START_XVFB environment variable to false, but forgot to actually run Firefox, Chrome or Edge in headless mode.

Mounting volumes to retrieve downloaded files

A common scenario is mounting a volume to the browser container in order to retrieve downloaded files. This works well in Windows and macOS but not without workarounds in Linux. For more details, check this well-documented issue.

For example, while using Linux, you might be starting a container in the following way:

docker run -d -p 4444:4444 --shm-size="2g" \
  -v /home/ubuntu/files:/home/seluser/Downloads \
  selenium/standalone-chrome:4.26.0-20241101

That will mount the host /home/ubuntu/files directory to the /home/seluser/Downloads inside the container (default browser's downloads directory). The problem happens because the volume will be mounted as root; therefore, the browser cannot write a file to that directory because it is running under the user seluser. This happens because that is how Docker mounts volumes in Linux, more details in this issue.

A workaround for this is to create a directory on the host and change its permissions before mounting the volume. Depending on your user permissions, you might need to use sudo for some of these commands:

mkdir /home/ubuntu/files
chown 1200:1201 /home/ubuntu/files

After doing this, you should be able to download files to the mounted directory. If you have a better workaround, please send us a pull request!

Mounting volumes to retrieve video files

Similar to mount volumes to retrieve downloaded files. For video files, you might need to do the same

mkdir /tmp/videos
chown 1200:1201 /tmp/videos

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