Docker

Introduction

The goal of this document to illustrate the use of docker and the Selenium project. The selenium project has released a number of containers to run various tools in the suite.

Why Docker?

Running a docker container standardises the build across OS’s and removes many of the issues user may have relating to JAVA/browser version/selenium version etc.

Preparing Docker on Windows

The following outlines preparing a windows 10 home installation to run docker containers.

Installing Docker

Depending on your version of windows there are currently two ways of running docker. Details are given at Docker. For the version of windows Being used in this vignette (win 10 home) the older Docker toolbox is what we are going to use to run containers.

Download the .exe for Docker toolbox and begin the install. Follow the instructions on the toolbox install windows page.

Clicking on the Docker Quickstart terminal link should eventually give you a terminal that resembles the following:

Preparing Docker on Linux

The following outlines preparing a ubuntu 16.04 installation to run docker containers.

Installing Docker

For a general guide for various Linux distros see Docker

Ubuntu 16.04

Run system update firstly

Add the official Docker GPG key to your system

Add the Docker repository to APT sources:

Update the package database:

Now you should be able to install Docker

Start the docker daemon.

You can check that the Docker is working by running a test container:

For now run as sudo

Running without sudo

If you want to run docker without sudo you can create a docker group and add the appropriate user to that group see Docker.

Using Selenium Docker Images

The official docker repository can be viewed here at Docker Hub.

What’s in an Image?

Lets examine the selenium/node-firefox image. The first thing to note is the Tags.

Clicking this gives us the various tagged versions of this image. Clicking Dockerfile allows us to view the source behind the image:

FROM selenium/node-base:2.53.0 
MAINTAINER Selenium <selenium-developers@googlegroups.com> 

USER root #========= 
# Firefox 
#========= 
ENV FIREFOX_VERSION 45.0.2

We can see that this image will run selenium server and contain firefox version 45.0.2.

We will be interested not in the node-firefox image but the selenium/standalone-firefox image. Looking at its Dockerfile we see however that it is built on the first image we looked at.

Pulling an Image

Windows 10 - Docker Toolbox

To get the image we are interested in we first click our quickstart link to open a terminal.

We then issue the following command:

Notice we appended a tag version so we are asking for the 2.53.0 version of this image.

Ubuntu 16.04

Similar to windows we use the docker pull command. If you did not create and add your user to a Docker group you will need to sudo

Start Your Servers!

When we run an image we refer to that instance of the running image as a container. Importantly for Selenium we are dealing with a server so we require a port. We will have a port on the container and a port on the host machine (the machine that is running the container). The only complexity will involve mapping the host port and container port.

By default the Selenium images expose port 4444 and use this port for serving. This is not a problem for us and we can map as we see fit on the host machine.

Windows 10 Running an Image

Again we run docker and this time use the run command.

For illustration here we are mapping the container port 4444 to the host port 4445 so when we want to refer to our server on the host machine we will use 4445 as the port.

We also run the ps command after running to show our current running containers.

So we can see an instance of standalone-firefox:2.53.0 is running. It has id=ac61567a8f06 and is named peaceful_aryabhata.

Ubuntu 16.04 Running an Image

For ubuntu we also issue a run command followed by a listing of running containers with ps.

Again run as sudo if necessary:

The Ubuntu container has id=5475923fc4dc and is named peaceful_payne.

A tip if you don’t want to strain your eyes is to use the --format argument:

NAMES               IMAGE                                CONTAINER ID
peaceful_payne      selenium/standalone-firefox:2.53.0   5475923fc4dc

RSelenium and Running Containers

Now that we have a container running a selenium server and its own firefox we can call it using RSelenium

Utilising the Firefox Standalone Container in Windows 10

With Windows 10 we have Docker toolbox which creates a virtual machine on windows to run our containers. So the virtual machine is the host rather than Win 10. We need the ip address of this virtual machine. This is the only added complication. We can get the ip address of the virtual machine using docker-machine.exe:

192.168.99.100

So as we can see the virtual machine has ip = 192.168.99.100 and as we noted previously we mapped port 4444 to port 4445 on the host (the virtual machine in this case). So we should have a Selenium server accessible on port 4445 of the virtual machine. Lets try it:

## [1] "Connecting to remote server"
## $applicationCacheEnabled
## [1] TRUE
## 
## $rotatable
## [1] FALSE
## 
## $handlesAlerts
## [1] TRUE
## 
## $databaseEnabled
## [1] TRUE
## 
## $version
## [1] "45.0.2"
## 
## $platform
## [1] "LINUX"
## 
## $nativeEvents
## [1] FALSE
## 
## $acceptSslCerts
## [1] TRUE
## 
## $webdriver.remote.sessionid
## [1] "bfe1c24d-8b17-4e64-a062-cba14e99472b"
## 
## $webStorageEnabled
## [1] TRUE
## 
## $locationContextEnabled
## [1] TRUE
## 
## $browserName
## [1] "firefox"
## 
## $takesScreenshot
## [1] TRUE
## 
## $javascriptEnabled
## [1] TRUE
## 
## $cssSelectorsEnabled
## [1] TRUE
## 
## $id
## [1] "bfe1c24d-8b17-4e64-a062-cba14e99472b"
## [[1]]
## [1] "Google"

So as expected we have version 45.0.2 of firefox running in Linux. We note that no browser popped up and we don’t see any signs in the MINGW64 console. This is expected the browser is headless. If you are using RStudio you can use the Viewer pane to get a screenshot remDr$screenshot(display = TRUE). Later we will see how we can run a debug version that uses VNC to allow us to interact with the containers browser.

Utilising the Firefox Standalone Container in Ubuntu 16.04

On our ubuntu 16.04 box life is simpler. The host in this case is the machine itself. The ip address is therefore localhost the default for RSelenium:

## [1] "Connecting to remote server"
## $applicationCacheEnabled
## [1] TRUE
## 
## $rotatable
## [1] FALSE
## 
## $handlesAlerts
## [1] TRUE
## 
## $databaseEnabled
## [1] TRUE
## 
## $version
## [1] "45.0.2"
## 
## $platform
## [1] "LINUX"
## 
## $nativeEvents
## [1] FALSE
## 
## $acceptSslCerts
## [1] TRUE
## 
## $webdriver.remote.sessionid
## [1] "644c353a-34b8-4bb4-bcff-746df5a30af8"
## 
## $webStorageEnabled
## [1] TRUE
## 
## $locationContextEnabled
## [1] TRUE
## 
## $browserName
## [1] "firefox"
## 
## $takesScreenshot
## [1] TRUE
## 
## $javascriptEnabled
## [1] TRUE
## 
## $cssSelectorsEnabled
## [1] TRUE
## 
## $id
## [1] "644c353a-34b8-4bb4-bcff-746df5a30af8"
## [[1]]
## [1] "Google"

Again we see that we have Firefox 45.0.2 running on Linux. So running docker containers allows us to run a standard setup OS independent and we don’t need to worry about machine specifics.

Debugging Using VNC

Often it is useful to be able to interact with the browser spawned by Selenium. In this regard the Selenium project provides debug versions of their images which include VNC. This means with a VNC viewer we can remote logon to the container and interact with the browser.

Remote Logging/Debugging with Windows

First lets stop the running container. To stop the running container we need its ID. We then pass this id to the stop command:

ac61567a8f06
ac61567a8f06
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES

So we have stopped our container and will have no issues with blocked ports. Next we need to pull the Firefox standalone debug image. Again this has various tags and we will choose the 2.53.0 one:

2.53.0: Pulling from selenium/standalone-firefox-debug

0be59000882d: Already exists
f20b6f990572: Already exists
53662c966c9f: Already exists
a3ed95caeb02: Already exists
0e449738cbb6: Already exists
63921592acdf: Already exists
8553f3252cbc: Already exists
dde80f7d7068: Already exists
232a7d285d74: Already exists
284e6949cb6f: Already exists
85909c621e51: Already exists
db03d98be095: Already exists
67898bba08c8: Already exists
23edc5cca893: Already exists
5ceef68785db: Already exists
8cbb6b75dad5: Already exists
d18b13cc4e51: Pull complete
4a3e92e6c855: Pull complete
1f5786a4b2ff: Download complete
3a29027ac709: Download complete
a70ecef6edbc: Download complete
10672504dfa1: Pull complete
1f5786a4b2ff: Pull complete
3a29027ac709: Pull complete
a70ecef6edbc: Pull complete
Digest: sha256:9b03c047b68b4e1c43f6d09edd952c1200766408104f76fa055e04028390491b
Status: Downloaded newer image for selenium/standalone-firefox-debug:2.53.0

Next we start the container as before. This time we have two ports to map. The Selenium port as before and also now the VNC port. The Selenium image expose the VNC port on 5900 by default and we map this port to a port on the host. We will choose 5901 just to illustrate host v container:

ee0c0bb8b711723e653ccc26219e314a37c28d2027f939046adcfc90a4beb645
192.168.99.100
NAMES               IMAGE                                      CONTAINER ID
focused_tesla       selenium/standalone-firefox-debug:2.53.0   ee0c0bb8b711

Again we note that the container is ran on a virtual machine not on our Windows 10 box so we expose the ip of said virtual machine. Next we download a VNC viewer if we don’t have one.

TightVNC has worked for me so I use it here.

Our Selenium server is running so lets use RSelenium again to browse to Google:

Now we open TightVNC and use the VM ip with appropriate port for VNC:

You will be asked for a password which is secret. This can be seen by reading the images dockerfile:

RUN apt-get update -qqy \
  && apt-get -qqy install \
    x11vnc \
  && rm -rf /var/lib/apt/lists/* \
  && mkdir -p ~/.vnc \
&& x11vnc -storepasswd secret ~/.vnc/passwd

Enter the password and you should have access to the container browser. Navigate to another website;

## [[1]]
## [1] "BBC - Homepage"

and you should observe the action on the containers browser. Finally stop your containers:

ee0c0bb8b711

Remote Logging/Debugging with Linux

Firstly, we stop any running containers which may block our ports:

5475923fc4dc
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES

Like in windows we pull the 2.53.0 version of the Firefox standalone debug image (again using sudo if necessary:

2.53.0: Pulling from selenium/standalone-firefox-debug

0be59000882d: Already exists 
f20b6f990572: Already exists 
53662c966c9f: Already exists 
a3ed95caeb02: Already exists 
0e449738cbb6: Already exists 
63921592acdf: Already exists 
8553f3252cbc: Already exists 
dde80f7d7068: Already exists 
232a7d285d74: Already exists 
284e6949cb6f: Already exists 
85909c621e51: Already exists 
db03d98be095: Already exists 
67898bba08c8: Already exists 
23edc5cca893: Already exists 
5ceef68785db: Already exists 
8cbb6b75dad5: Already exists 
d18b13cc4e51: Pull complete 
4a3e92e6c855: Pull complete 
10672504dfa1: Downloading 7.915 MB/16.87 MB
1f5786a4b2ff: Downloading 5.487 MB/5.528 MB
3a29027ac709: Download complete 
a70ecef6edbc: Download complete

Once the image is downloaded we can start it as we did with Windows. We map Selenium to port 4445 on the host and VNC to port 5901. As noted before the host in the case of Ubuntu 16.04 is the machine itself so localhost is the relevant ip:

dd36811562e83e66ab145efcedca2825a621741f10d8c81a5fb3fb5ba3019032
NAMES               IMAGE                                      CONTAINER ID
thirsty_swanson     selenium/standalone-firefox-debug:2.53.0   dd36811562e8

So we can see that Selenium server is running. Like in Windows we need a VNC viewer. You can use TightVNC as with windows and a guide to running it is here. We will use Vinagre however. A guide to install Vinagre is here. Basically we just need to apt-get it:

Again, we navigate to Google:

## [[1]]
## [1] "Google"

Now open Vinagre and input the correct ip/port (127.0.0.1:5901 in this case):

Again it will ask for a password which as before is secret.

You should now be able to interact with the containers browser. Again navigate to another website and observe the containers browser:

## [[1]]
## [1] "BBC - Homepage"

Finally close the session:

remDr$close()

And close down any running containers:

dd36811562e8