Docker behind a proxy

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In this post I will explain how to set up docker when you are behind corporate proxy.

All Internet tutorials about any technology take assumption that you are not behind a proxy. Working for my client that must use corporate proxy, I spent a lot of working hours discovering how to use docker behind  a proxy.

You first need to find out value for corporate proxy. In corporate environment, this could be rather tricky action, because that value is not always publicly known.

  1. Set docker systemd settings to use proxy.

Use official docker instructions [source]. With this setting, docker daemon nows how to get images from the Internet.

2. Dockerfile.

If you need to tailor your own image, you need to use Dockerfile. In order to enable Dockerfile commands to get stuff from the Internet, you need to set ENV HTTP_PROXY variable.

After FROM directive in Dockerfile, put following settings:

FROM image_name
ENV http_proxy <HTTP_PROXY>
ENV https_proxy <HTTPS_PROXY>

3. Some tools do not use environment variable http_proxy.

There are some tools that made a wrong design decision where they do not use environment variable http_proxy, but they require that command switch must be used in order to set proxy value.

I broke my teeth on following tools:

  • pip
  • npm

Here is simple heuristic. If command from Dockerfile gets timeout (usually it appears to hang when it can not get to Internet), consult documentation for this command to find out how to set proxy value.

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How to replace curl data-binary value to form-data upload parameters

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In this post I will explain how master Joda visited me in my dream and asked me important question about one of my previous blog posts: How to measure upload speed of web application upload form [link]. The post provided right information about curl parameter that enables you to see upload speed. But curl example for upload file is wrong!

I found that is wrong when I tried to measure upload speed in real application. And realized that file is not uploaded in application. By observing the copy pasted curl, I noticed that there was not Content-Length header. Bingo, lets create Chrome developer tools issue ticket[link].

Please read comments, because I learned a lot about curl upload file feature. Google developers who answered my ticket did not just dismissed my wrong curl upload file heuristic, they took extra step and educated me!

So, in order to use curl upload file feature, you need to transform something like this:

--data-binary $'------WebKitFormBoundaryoeJQRnHeojsIBayU\r\nContent-Disposition: form-data; name="fileType"\r\n\r\n5\r\n------WebKitFormBoundaryoeJQRnHeojsIBayU\r\nContent-Disposition: form-data; name="file"; filename="elixir-websetup.exe"\r\nContent-Type: application/x-msdownload\r\n\r\n\r\n------WebKitFormBoundaryoeJQRnHeojsIBayU--\r\n'

into this:

-F file=@elixir-websetup.exe -F fileType=5

You can now data-binary parameter and its value from curl.

It is important to have check mechanism for upload file. Use your application features to check is file really uploaded. curl can also help by observing application returned value.

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What is happening in our application?

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In this post, I will try to elaborate why is often expected from me as a tester to create meaningful application error messages.

So, you are using some web application, and you get something like this( thanks to Evil Tester):

Screen Shot 2017-01-14 at 2.04.02 PM

And that error message does not tell you anything about your action or input. At least they put disclaimer: “That is all we know”.

While I am testing application, I find a lot of such not informative error messages. Why I find them and developers not? Because I know how to make reasonable scenarios that trigger those errors. And to come up with such scenarios and test data is not something of interest of regular developer. In my experience they find this very boring and not creative job. But I think that finding alternative flows by exploring api that you use is very creative and important job.

Developers just have different meaning for definition of DONE. Or they are just lazy.

First line of defense is that user will never do that. But you took BBST Bug advocacy, and you have already uncornered your test scenarios making it more probable in real life.

After I talk to project leader and provide him information about low quality error messages, I put extra work on my shoulders. Karlo, as you already found those error messages, you will create meaningful error messages.

The problem here is that I can only provide error messages for scenarios that I covered. But low level mechanics of the application, which includes inter module cooperation based on api contracts, this is developer responsibility.


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Selenium webdriver Net::ReadTimeout (Net::ReadTimeout) exception

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In this post I will explain how I resolved this exception in context of selenium webdriver testing in headless mode using xvfb on linux.

You finally managed to set up linux and xvfb server, your selenium webdriver settings are correct, and you successfully run your first scenario in headless mode! Astonishing achievement when I add fact that you only used open source technology.

You have your cucumber feature files with scenarios, written according every best BDD practice. Although, one feature file has more scenarios than other. Feature that it tests is rather complicated.

You set up jenkins job, and find out in the next morning of run, that only that feature file has failures. You examined execution html log, and find out this cryptic exception:


Network timeout!? But site that you test is ready and online.

What is going on under the hood of selenium webdriver tests.

Selenium webdriver is http server. It accepts http connections, according to webdriver protocol that is http based. Your language selenium webdriver bindings start server for you when you create driver and your test script sends webdriver protocol commands to webdriver server. Simple as that.

Above exception means that your selenium webdriver server is not responding. Why? In context of headless xvfb linux test run, this could be caused by various reasons.


I noticed that exception appeared always on same scenario, so I split long cucumber feature file in two. If you have properly written feature file according to BDD practices, this should not affect your test suite.

I guess My heuristic is that selenium webdriver server could be up for some limited time and that with long feature file I hit that limit.

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