Mugurel Tudor

Category: Technology

  • Taming PagerDuty on iOS

    I’ve switched recently to PagerDuty for oncall notifications and, being a new app for me, I left it on default settings for some days, to get a general feeling of it.

    While on default settings it achieves its main purpose (to make you aware there’s an issue) it’s also horribly disturbing. Because it’s using “Critical Alerts” facility on iOS, it overwrites the normal sound volume and sound alert and it just makes a very loud… alerting noise, that will give you a heart attack. If it’s when you sleep, it will do the same thing for you AND your significant other. While “Critical Alerts” should be like this because they are… well… critical, I think in this case it’s abused by Pager Duty. OK, somewhere a piece of infrastructure has issues, it’s not an earthquake.

    So that was the first thing I modified in settings. Exit Critical Alerts, enter Sad Trombone sound. A lot better.

    Now, what to do during the nights? OK, it’s a Sad Trombone, but it will still wake you AND your significant other. And only one is getting paid here.

    Enter any fitness smart band. I bought a Xiaomi Mi Smart Band 6, which is probably the cheapest decent thing you can buy (37€ on amazon.de), but you can also try any other cheap random band. The important thing is, to have an app that is able to forward app notifications / phone calls to your band so it would vibrate.

    The first thing I had in mind was to just forward the app notifications / phone calls to my band, but unfortunately on iOS, even if you do that, the phone will still ring. Apps are not allowed to modify the sound volume on iOS devices.

    Fine, next thing I tried was to activate this AND silent hours. But if you do this, then instead of getting the call forwarded, the call from PagerDuty is discarded by iphone. You get nothing. Still not OK.

    Fine. I set the phone on silent (from the hardware button) and activated the app / phone forwarding. Now it works as expected, on alerts my fitness band vibrates, phone doesn’t make a sound, I am able to wake up and my wife won’t hear a thing. It sounds good, but what happens if there’s a problem with the band? If it crashes, or it’s falling from my hand, or bluetooth decides to whatever and not work: you would wake up in the morning with the entire infrastructure burning for several hours already.

    I “fixed” this by adding an additional action on PagerDuty, to call me on my private phone. That is not silenced during the night, for phone calls, when I’m on call. So now, if I get an alert, I’ll get a short vibrate on my hand, that would wake me. If I’m in a deep sleep and that’s not enough, I will get a phone call on my work phone (or 2, or 3, you know you better) that would vibrate like hell on my hand and would wake me up. Phone would still be silent. And if somehow this doesn’t work, then the last action would be to get a phonecall on my private phone, which would wake me (and the rest of the house, but oh well). But this, until then, never happened. I found the band connection to be very stable.

    So to make a summary:

    • remove “Critical Alerts” option and put a decent sound and a decent volume
    • pair your work phone with a fitness band
    • activate the app / calls forwarding to the fitness band (I use Mi Fit app, works like a charm)
    • add an extra action in PagerDuty to be called on your private phone (a catch all)
    • set your business phone on silent during the night

    Your family will be very grateful for this setup. And your health as well.

  • Progress bars in Python

    If you need to add a progress bar in a python script, while you slowly loop over some items: before starting creating your own, save your time and consider tqdm.

    • pip install tqdm
    • wrap your iterable: tqdm(iterable)
    • profit!

    So for example, something like this:

    from tqdm import tqdm
for pages in tqdm(mypages[myissue], unit='page'):
    process_my_page()

    You can customize quite a lot of things (like labels, units, position, color, etc) so check the fine manual.

    It is THAT simple!

  • Using build variables in Packer

    In case you want to use an unsupported Packer provisioner like testinfra, you need to make it work with “shell” or “shell (local)”, but you will soon have a dilemma:

    • You would prefer to run it with “shell (local)” from your build machine and get easy access to your junit log files, but Packer documentation makes you believe you can only run local jobs
    • You can also use “shell”, but then you need to upload your tests, install the dependencies, run your tests, fetch your test results back and then cleanup after yourself. It seems like a lot of unnecessary extra steps.

    Luckily, there are some contextual build variables available, but Hashicorp managed to hide them in a completely random documentation location. You would need usually {{build `SSHPrivateKey`}}, {{build `User`}} and {{build `Host`}} to get access to the temporary ssh private key that packer is using, the temporary host IP and the username used by packer.

    Getting back to our testinfra example, then you could do something like this:

    {
    "type": "shell-local",
    "inline": [
        "echo '{{build `SSHPrivateKey`}}' > packer_rsa",
        "chmod 600 packer_rsa",
        "pytest --ssh-identity-file=packer_rsa --ssh-config=ssh_config \
        --hosts=ssh://{{build `User`}}@{{build `Host`}} \
        --junit-xml junit.xml testinfra_test.py"
    ]
}

    where in ssh_config you may want to disable StrictHostKeyChecking, as with every build you’ll get a new HostKey.

  • Using Python virtual environments with direnv

    If you are using python you know the pain of keeping your system in a clean state. Usually your OS will come with some python(s) by default, but very easily you discover you need some extra modules that you’ll have to install with pip. And from here you go on a slippery slope and end up with 5 pythons, modules installed in 10 different locations and random conflicts that will puzzle you.

    In order to “fix” this the recommended way is to use a separate virtual environment for your projects, or one virtual environment per project, where you install only the modules you need without making the OS “dirty”. Making use of this would be something like this:

    $ python3 -m venv myenv
$ source myenv/bin/activate

(myenv) $ pip3 --version
pip 20.2.3 from /Users/me/myenv/lib/python3.9/site-packages/pip (python 3.9)
(myenv) $ deactivate

$ pip3 --version
pip 20.2.4 from /usr/local/lib/python3.9/site-packages/pip (python 3.9)

    Now, if you’re lazy, you already see a problem here: you need to remember to load this special environment every time, and then to unload it. Enter direnv.

    After you install direnv (on MacOS that would be an easy “brew install direnv”), you need to hook it to your bash. For this, you need to add something like this to your .bashrc:

    eval "$(direnv hook bash)"

    Now go ahead and create an .envrc file in your project folder that will manage the new virtualenv for you. You need to accept the new .envrc file first (this is for security reasons, otherwise you might end up with a wiped laptop after you do a git pull from some malicious repo), and after this magic will happen: the virtualenv will be automatically loaded whenever you enter that folder, and automatically unloaded when you exit it.

    $ cd myproject

$ echo "layout_python3" > .envrc
direnv: error /Users/me/myproject/.envrc is blocked. Run `direnv allow` to approve its content

$ direnv allow
direnv: loading ~/myproject/.envrc
direnv: export +VIRTUAL_ENV ~PATH

$ pip3 --version
pip 20.2.3 from /Users/me/myproject/.direnv/python-3.9.0/lib/python3.9/site-packages/pip (python 3.9)
$ cd ..
direnv: unloading
$ pip3 --version
pip 20.2.4 from /usr/local/lib/python3.9/site-packages/pip (python 3.9)

$ cd myproject/
direnv: loading ~/myproject/.envrc
direnv: export +VIRTUAL_ENV ~PATH
$ pip3 --version
pip 20.2.3 from /Users/me/myproject/.direnv/python-3.9.0/lib/python3.9/site-packages/pip (python 3.9)

    It’s magic!