WebElement.click()

So to demonstrate the concept we’ll prepare the "local cluster" with the help of Docker and official Selenium and Nginx docker images. We also build our own image derived from Nginx image that would include the configuration allowing us to compress Selenium traffic.

As the final steps we will check the result with curl tool and simple Selenium test.

For the sake of demonstration we will prepare an isolated network space where our components will be running. The model we will implement is really very close to what people have in their distributed environments. Let’s add virtual network to our system. It is really simple:

We have just added a virtual network of bridge type. We can refer to that new network using the name grid.

Our next steps would be to prepare reverse proxy image, and run it and Selenium image within just created virtual network.

Now we’re building the image that would be running reverse proxy which will be compressing traffic on the fly. Fortunately Nginx server allows to configure such proxy with few lines of configuration. Let’s create a separate folder where we will be keeping all the files needed to build an image. Change your directory to that new folder and add file named Dockerfile with the following content:

This file will later tell Docker that we take the default official image of Nginx server and add the configuration file that we do not yet have. Let’s add one to the same folder. Name it nginx.conf and put the following content to that new file:

Now everything is ready. The proxy with such the configuration will be listening on the port 4444 and would forward all the requests (for all the paths) to http://selenium-hub:4444 which will be resolved to the container where our remote driver/hub is running.

First of all we need to build our custom Nginx image. When you are in that created folder, execute the command:

1) Build reverse proxy image

The resulting output should end with the lines like these:

2) Start Selenium container

This means we can now start the reverse-proxy. However before we do that we need to start the official Selenium container that packages WebDriver, Selenium Grid and web browser. In my example I use image with Google Chrome standalone (which means grid is configured to support only a single session), but you may choose among Chrome, Firefox and Opera.

This command starts an image within recently created network named as grid and the virtual host in that virtual network will get the name selenium-hub.

In a few seconds you should see the log message saying the service has started on port 4444. The port mentioned there is so called "container port" which means it is accessible only from other containers of the same virtual network (unless explicitly exposed).

3) Start reverse proxy container

Now open new terminal (or new command line). Start reverse proxy with the following command:

This command starts our custom Nginx image within the virtual network the same as just started Selenium container. This command also exposes internal container port of Nginx (4444) to the host port 12345. You can now open your browser and navigate to http://localhost:12345/. Browser will display Selenium welcome message and the terminal where your proxy is running should log those requests.

4) Make a smoke test

Open new terminal/command line so that you have both reverse proxy log and your new terminal displayed. In your new terminal run the following command:

Curl tool responds with some human readable page content. At the same time Nginx console shows the log line that contains the information about request type (GET), protocol used (HTTP 1.1), response code (200), content size (in my case it is 1672 bytes) and user-agent (in my case it is "curl/7.68.0").

Now run slightly modified command:

The output of curl now showing new header came with server response: "Content-Encoding: gzip". It also shows that the data transferred with the response is now two times smaller. The same is confirmed by Nginx logs.

All the interaction with the browser through the WebDriver are bound to a session object. To create one you need to invoke dedicated endpoint. When create a session, WebDriver starts a web browser.

The previous command should output the session details. Take session id from there and use it instead of 88e2296bfa38e745be8d01f78a2399d3 in all the following commands:

Now we’re going to take a screen shot. The response won’t be compressed because we do not specify the expected compression method in dedicated header.

Observe your current folder. You should now see base64.scr file created. Open it for edit, remove {"value":" from the beginning and "} from the end. Save the changes.

This file is encoded with BASE64 encoding. If you work in Linux, you probably have base64 tool that can help you to decode the file. Otherwise you can use some online decoders.

Observe your current folder. There is new PNG file there. Open it in any image viewer to make sure it is the properly formatted image file.

Let’s now add some compression to the response from Selenium WebDriver.

Now you should have one new file in your folder. That test.gz file contains compressed response of the same command as you were running before without compression.

The command below will kill the WebDriver session and close the browser window.