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/

Quick start

Start a Docker container with Firefox

docker run -d -p 4444:4444 -p 7900:7900 --shm-size="2g" selenium/standalone-firefox:4.1.2-20220217

Point your WebDriver tests to http://localhost:4444
That's it!
(Optional) To see what is happening inside the container, head to http://localhost:7900 (password is secret).

More details about visualising the container activity, check the Debugging section.

☝️ 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.

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

Experimental Mult-Arch aarch64/armhf/amd64 Images

For experimental docker container images, which run on platforms such as the Mac M1 or Raspberry Pi, see the community driven repository hosted at seleniumhq-community/docker-seleniarm. These images are built for three separate architectures: linux/arm64 (aarch64), linux/arm/v7 (armhf), and linux/amd64.

Furthermore, these experimental container images are published on Seleniarm Docker Hub registry.

See issue #1076 for more information on these images.

If you're working on an Intel or AMD64 architecture, we recommend using the container images in this repository (SeleniumHQ/docker-selenium) instead of the experimental ones.

Execution modes

Standalone

Firefox

docker run -d -p 4444:4444 --shm-size="2g" selenium/standalone-firefox:4.1.2-20220217

Chrome

docker run -d -p 4444:4444 --shm-size="2g" selenium/standalone-chrome:4.1.2-20220217

Edge

docker run -d -p 4444:4444 --shm-size="2g" selenium/standalone-edge:4.1.2-20220217

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:4.1.2-20220217
$ 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:4.1.2-20220217
$ 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:4.1.2-20220217
$ 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:4.1.2-20220217

Windows PowerShell

$ docker network create grid
$ docker run -d -p 4442-4444:4442-4444 --net grid --name selenium-hub selenium/hub:4.1.2-20220217
$ 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:4.1.2-20220217
$ 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:4.1.2-20220217
$ 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:4.1.2-20220217

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:4.1.2-20220217

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:4.1.2-20220217

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:4.1.2-20220217

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:4.1.2-20220217

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:4.1.2-20220217

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:4.1.2-20220217

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:4.1.2-20220217

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:4.1.2-20220217

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:4.1.2-20220217

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

Video recording

Tests execution can be recorded by using the selenium/video:ffmpeg-4.3.1-20220217 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 🎉

Notes:

If you have questions or feedback, please use the community contact points shown here.
Please report any bugs through GitHub issues, and provide all the information requested on the template.
Video recording for headless browsers is not supported.
Video recording tends to use considerable amounts of CPU. Normally you should estimate 1CPU per video container, and 1 CPU per browser container.
Videos are stored in the /videos directory inside the video container. Map a local directory to get the videos.
If you are running more than one video container, be sure to overwrite the video file name through the FILE_NAME environment variable to avoid unexpected results.

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:4.1.2-20220217
$ docker run -d --net grid --name video -v /tmp/videos:/videos selenium/video:ffmpeg-4.3.1-20220217
# 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

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.

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:4.1.2-20220217", "{\"browserName\": \"firefox\"}",
    "selenium/standalone-chrome:4.1.2-20220217", "{\"browserName\": \"chrome\"}",
    "selenium/standalone-edge:4.1.2-20220217", "{\"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-4.3.1-20220217"

# 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>

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:4.1.2-20220217
$ 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/bin/config.toml \
    -v ${PWD}/assets:/opt/selenium/assets \
    -v /var/run/docker.sock:/var/run/docker.sock \
    selenium/node-docker:4.1.2-20220217

Windows PowerShell

$ docker network create grid
$ docker run -d -p 4442-4444:4442-4444 --net grid --name selenium-hub selenium/hub:4.1.2-20220217
$ 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/bin/config.toml `
    -v ${PWD}/assets:/opt/selenium/assets `
    -v /var/run/docker.sock:/var/run/docker.sock `
    selenium/node-docker:4.1.2-20220217

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/bin/config.toml \
    -v ${PWD}/assets:/opt/selenium/assets \
    -v /var/run/docker.sock:/var/run/docker.sock \
    selenium/standalone-docker:4.1.2-20220217

Windows PowerShell

docker run --rm --name selenium-docker -p 4444:4444 `
    -v ${PWD}/config.toml:/opt/bin/config.toml `
    -v ${PWD}/assets:/opt/selenium/assets `
    -v /var/run/docker.sock:/var/run/docker.sock `
    selenium/standalone-docker:4.1.2-20220217

Using Dynamic Grid in different machines/VMs

Hub - Machine/VM 1

$ docker run -d -p 4442-4444:4442-4444 --name selenium-hub selenium/hub:4.1.2-20220217

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/bin/config.toml \
    -v ${PWD}/assets:/opt/selenium/assets \
    -v /var/run/docker.sock:/var/run/docker.sock \
    selenium/node-docker:4.1.2-20220217

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/bin/config.toml `
    -v ${PWD}/assets:/opt/selenium/assets `
    -v /var/run/docker.sock:/var/run/docker.sock `
    selenium/node-docker:4.1.2-20220217

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:4.1.2-20220217", "{\"browserName\": \"firefox\"}",
    "selenium/standalone-chrome:4.1.2-20220217", "{\"browserName\": \"chrome\"}",
    "selenium/standalone-edge:4.1.2-20220217", "{\"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-4.3.1-20220217"

# 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

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.

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 commandline 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:4.1.2-20220217

JAVA_OPTS Java Environment Options

You can pass JAVA_OPTS environment variable to java process.

$ docker run -d -p 4444:4444 -e JAVA_OPTS=-Xmx512m --name selenium-hub selenium/hub:4.1.2-20220217

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.

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 --shm-size="2g" selenium/node-chrome:4.1.2-20220217

Setting Screen Resolution

By default, nodes start with a screen resolution of 1360 x 1020 with a color depth of 24 bits and a dpi of 96. These settings can be adjusted by specifying SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_DEPTH, and/or SCREEN_DPI environmental variables when starting the container.

docker run -d -e SCREEN_WIDTH=1366 -e SCREEN_HEIGHT=768 -e SCREEN_DEPTH=24 -e SCREEN_DPI=74 selenium/standalone-firefox

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. 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 on 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 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 a 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 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 START_XVFB=false --shm-size="2g" selenium/node-chrome

For more information, see this GitHub issue.

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 variable 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.

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 by 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 4444:4444 --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:4.1.2-20220217
$ docker run -d --net grid -e HUB_HOST=selenium-hub --shm-size="2g" selenium/node-chrome:4.1.2-20220217
$ docker run -d --net grid -e HUB_HOST=selenium-hub --shm-size="2g" selenium/node-edge:4.1.2-20220217
$ docker run -d --net grid -e HUB_HOST=selenium-hub --shm-size="2g" selenium/node-firefox:4.1.2-20220217

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.

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

set -e

cmd="$@"

while ! curl -sSL "http://localhost:4444/wd/hub/status" 2>&1 \
        | jq -r '.value.ready' 2>&1 | grep "true" >/dev/null; do
    echo 'Waiting for the Grid'
    sleep 1
done

>&2 echo "Selenium Grid is up - executing tests"
exec $cmd

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.

Debugging

This project uses x11vnc as VNC server to allow users 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 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:4.1.2-20220217
$ docker run -d -p 4445:4444 -p 5901:5900 --shm-size="2g" selenium/standalone-edge:4.1.2-20220217
$ docker run -d -p 4446:4444 -p 5902:5900 --shm-size="2g" selenium/standalone-firefox:4.1.2-20220217

Then, you would use in your VNC client:

Port 5900 to connect to the Chrome container
Port 5901 to connect to the Edge container
Port 5902 to connect to the Firefox container

If you get a prompt asking for a password, it is: secret. If you wish to change this, you should either change it in the /NodeBase/Dockerfile and build the images yourself, or you can define a Docker image that derives from the posted ones which reconfigures it:

#FROM selenium/node-chrome:4.1.2-20220217
#FROM selenium/node-edge:4.1.2-20220217
#FROM selenium/node-firefox:4.1.2-20220217
#Choose the FROM statement that works for you.

RUN x11vnc -storepasswd <your-password-here> /home/seluser/.vnc/passwd

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

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

Using your browser (no VNC client is needed)

This project uses noVNC to allow users inspect visually container activity with their browser. This might come 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 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:4.1.2-20220217
$ docker run -d -p 4445:4444 -p 7901:7900 --shm-size="2g" selenium/standalone-edge:4.1.2-20220217
$ docker run -d -p 4446:4444 -p 7902:7900 --shm-size="2g" selenium/standalone-firefox:4.1.2-20220217

Then, you would use in your browser:

http://localhost:7900/ to connect to the Chrome container
http://localhost:7901/ to connect to the Edge container
http://localhost:7902/ to connect to the Firefox container

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

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

The reason might be that you've set the 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/files \
  selenium/standalone-chrome:4.1.2-20220217

That will mount the host /home/ubuntu/files directory to the /home/seluser/files inside the container. The problem happens because the volume will be mounted as root, and 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 the 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!

Name		Name	Last commit message	Last commit date
Latest commit History 1,022 Commits
.github		.github
Base		Base
Distributor		Distributor
EventBus		EventBus
Hub		Hub
NodeBase		NodeBase
NodeChrome		NodeChrome
NodeDocker		NodeDocker
NodeEdge		NodeEdge
NodeFirefox		NodeFirefox
Router		Router
SessionQueue		SessionQueue
Sessions		Sessions
Standalone		Standalone
StandaloneChrome		StandaloneChrome
StandaloneDocker		StandaloneDocker
StandaloneEdge		StandaloneEdge
StandaloneFirefox		StandaloneFirefox
Video		Video
chart/selenium-grid		chart/selenium-grid
tests		tests
.editorconfig		.editorconfig
.gitignore		.gitignore
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE.md		LICENSE.md
Makefile		Makefile
README.md		README.md
docker-compose-v2.yml		docker-compose-v2.yml
docker-compose-v3-dev.yml		docker-compose-v3-dev.yml
docker-compose-v3-dynamic-grid.yml		docker-compose-v3-dynamic-grid.yml
docker-compose-v3-full-grid-dev.yml		docker-compose-v3-full-grid-dev.yml
docker-compose-v3-full-grid-swarm.yml		docker-compose-v3-full-grid-swarm.yml
docker-compose-v3-full-grid.yml		docker-compose-v3-full-grid.yml
docker-compose-v3-swarm.yml		docker-compose-v3-swarm.yml
docker-compose-v3-video.yml		docker-compose-v3-video.yml
docker-compose-v3.yml		docker-compose-v3.yml
generate_release_notes.sh		generate_release_notes.sh
logo.png		logo.png
tag_and_push_browser_images.sh		tag_and_push_browser_images.sh
update_tag_in_docs_and_files.sh		update_tag_in_docs_and_files.sh

License

rodcts/docker-selenium

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Docker images for the Selenium Grid Server

Community

Contents

Quick start

Experimental Mult-Arch aarch64/armhf/amd64 Images

Execution modes

Standalone

Hub and Nodes

Docker networking

macOS/Linux

Windows PowerShell

Using different machines/VMs

Hub - Machine/VM 1

Node Chrome - Machine/VM 2

macOS/Linux

Windows PowerShell

Node Edge - Machine/VM 3

macOS/Linux

Windows PowerShell

Node Firefox - Machine/VM 4

macOS/Linux

Windows PowerShell

Node Chrome - Machine/VM 4

macOS/Linux

Windows PowerShell

Docker Compose

Version 2

Version 3

Version 3 with Swarm support

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

Video recording

Dynamic Grid

Configuration example

Execution with Hub & Node roles

macOS/Linux

Windows PowerShell

Execution with Standalone roles

macOS/Linux

Windows PowerShell

Using Dynamic Grid in different machines/VMs

Hub - Machine/VM 1

Node Chrome - Machine/VM 2

macOS/Linux

Windows PowerShell

Execution with Docker Compose

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

Deploying to Kubernetes

Configuring the containers

SE_OPTS Selenium Configuration Options

JAVA_OPTS Java Environment Options

Node configuration options

Setting Screen Resolution

Grid Url and Session Timeout

Session request timeout

Increasing session concurrency per container

Running in Headless mode

Building the images

Waiting for the Grid to be ready

Adding a HEALTHCHECK to the Grid

Using a bash script to wait for the Grid

Debugging

Using a VNC client

Using your browser (no VNC client is needed)

Troubleshooting

--shm-size="2g"

Headless

Mounting volumes to retrieve downloaded files

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