Fixing Docker on Linode (Linux v4.18.16)

This week as I had some downtime after PyCon Canada, I started working on resolving all the issues that I postponed. One of these issues involved applying security updates to my Linode server and rebooting the server. However when I did so… I noticed that the Rookeries site went down. When I logged into the server, I quickly found the problem: Docker refused to start after the kernel updates.

As this bug report on Docker for Linux says, there is an issue with the latest Linode kernel when it comes to OverlayFS.

This causes the containerdservice that docker-ce is dependent on to not start. When looking at the logs (using sudo journalctl -xe), you’ll see an error along the lines of:

modprobe: ERROR: ../libkmod/libkmod.c:514 lookup_builtin_file() could not open builtin file '/lib/modules/4.18.16-x86_64-linode118/modules.builtin.bin'
modprobe: FATAL: Module overlay not found in directory /lib/modules/4.18.16-x86_64-linode118)

Thankfully there is a workaround to resolve this problem. From the instructions you need to an override configuration for the containerd service:

$ mkdir -p /etc/systemd/system/containerd.service.d/
$ cat << EOF > /etc/systemd/system/containerd.service.d/override.conf [Service]
ExecStartPre=
EOF
$ systemctl reload
$ systemctl restart docker

Anyways, I hope this helps if you run into the same situation.

To Make or Not to Make – Using cargo make for Rookeries v0.12.0

I was pleasantly surprised when my last blog post about migrating to Rust’s integration tests really took off on Twitter. I did not quite expect that much interest. 🙂

Using cargo-make

I recently continued with my exploration of Rust through Rookeries (my attempt at a static site generator/backing API server). This time I worked on switching over from using invoke and GNU make to using a nice build system called cargo-make. Overall I am quite happy with the result. To give you a taste of how cargo-make describes build tasks and environment variables, I included a short snippet from the Rookeries Makefile.toml below:

<br />
[env]
SERVER_PORT = "5000"

[tasks.build-js]
description = "Build JS frontend."
command = "npm"
args = ["run", "build"]

[tasks.run-dev-server]
description = "Run a Rookeries dev server."
command = "cargo"
args = ["run", "--", "run", "${SERVER_PORT}"]
dependencies = ["build-js"]

Much like invoke and Make, you can specify dependencies. Unlike Make, there is no weird tab-based syntax, or implicit behaviour that requires a look up in the GNU Make manual. Just a simple TOML file. Environment variables can be specified in standalone .env files, passed in or specified in the Makefile.toml itself, and allow for variables specified during a run to override defaults, etc. cargo-make also lets you use conditional logic but I did not need to use that for my purposes.

For Rookeries, I ended up creating locally running tasks, and versions for the Dockerized build setup that I have in CircleCI. Also I ended up using the scripting support that cargo-make provides for preparing the database for, and running the integration tests.

My Thoughts on CouchDB for Rookeries and Rust

I feel I cheated a bit towards the end especially by using a few curl commands to instantiate the CouchDB database, and with running the API integration tests. Maybe I should of wrote a proper CouchDB library and utility. However I decided against it, simply because I want move away from CouchDB for Rookeries. So I may not want to invest that much time in maintaining a proper database client if I’ll end up switching over to using Postgresql via diesel.rs Originally, I started using CouchDB because I use it heavily at my work at Points. As time goes on, I find myself more and more reluctant with using CouchDB, just because of all the issues I’ve experienced at work. That said, if someone wants me to maintain a CouchDB Rust library/CLI based on the code I have for Rookeries, then please reach out to me. The CouchDB crates I saw in crates.io did not inspire me, so I wrote my own CouchDB module in Rust. But I don’t want to maintain that code just for myself, so if anyone actually needs a proper CouchDB crate and wants me to maintain it, please reach out to me.

Update – Sofa Library

After I wrote this blog post originally, I did not know about this nice CouchDB crate called sofa. If I had know about it, I would of not bothered with my own implementation.

New Release of Rookeries – Now 100% Rust

Finally since this migration was a bit of work, so I decided to release a new version of Rookeries. Since the invoke setup was the last Python code, Rookeries is now 100% completely written in Rust. (And the JS frontend naturally.) The Rookeries Docker image is available on Docker Hub. The project is still quite in flux, and what I will work on next depends on what I need to do to hook up Rookeries to one of my Gatsby powered sites.

Writing Integration Tests in Rust + Releasing Rookeries v0.11.0

As part of my overall change over in Rookeries, from Python to Rust, I rewrote a suite of integration tests for the server API. To celebrate my successful transition, I released version 0.11.0 of Rookeries, whose tests use pure Rust now!

I found the rewrite not too cumbersome, thanks to the wonderful guide in the Rust book on integration tests. I did miss pytest’s fixture setup, which makes testing really easy. Especially when setting up fixtures that are run only once per test suite. That said, a single session setup makes it difficult to run tests in parallel. And while I ran into some inconsistent tests, I had the exact same kind of problems in Python. Basically my data model for Rookeries, doesn’t work well for singleton data like a single site. In the future, I plan on having a single Rookeries instance managing multiple different sites, so this point of not having a single test setup is ultimately moot.

Building a common setup module turned out to be more work than I imagined. I could not use macros because of the package setup. Also since tests are compiled individually, some methods in the common module, simply are not called, leading to warning of dead code.

What made the transition is easy was using the reqwest crate, and heavy use of serde_json’s json! macro. Comparing the Python and Rust version of the tests, makes them look very comparable.

Rust Version src:

#[test]
fn test_authenticated_user_cannot_modify_site_using_bad_request() {
    test_site();
    let api_base_uri = common::api_base_url();
    let client = Client::new();
    let auth_token = auth_token_headers();
    let response = client
        .put(api_base_uri.join("/api/site").unwrap())
        .body("")
        .header(Authorization(auth_token))
        .send()
        .unwrap();

    assert_bad_request_response(response);
}

fn assert_bad_request_response(mut response: Response) {
    let expected_response_json = json!({
        "error": {
            "status_code": 400,
            "message": "Bad request",
        }
    });

    assert_eq!(response.status(), StatusCode::BadRequest);
    let actual_json_response = response.json::<Value>().unwrap();
    assert_eq!(actual_json_response, expected_response_json);
}

Python Version src:

def test_authenticated_user_cannot_modify_site_using_bad_request(
        auth_token_headers, api_base_uri, test_site):
    response = requests.put(
        url=f'{api_base_uri}/api/site',
        data='',
        headers=auth_token_headers,
    )
    assert_bad_request_response(response)

def assert_bad_request_response(response):
    expected_response_json = {
        'error': {
            'status_code': http.HTTPStatus.BAD_REQUEST.value,
            'message': mock.ANY,
        }
    }

    assert response.json() == expected_response_json
    assert response.status_code == http.HTTPStatus.BAD_REQUEST

I am pretty happy with how everything turned out overall. My next bit of Rookeries work will be migrating away from invoke and make to cargo make.

Rookeries v0.10.0 – Rust Re-write

I just rewrote Rookeries in Rust, and the latest version is now available as a Docker image on Docker Hub. (This is why I have not responded to emails in a bit… I’ve been doing a lot of thinking of what I want to do next.)

So why a rewrite? Ultimately I decided to change the direction of Rookeries as a project (making it more of a static site generation tool + headless CMS). I also wanted to improve my knowledge of Rust. (A programming language that I believe is quietly revolutionizing computing bit by bit. I really need to write about it sometime) But to show that there is reason for my madness:

Traditional CMS

I realized that my approach to Rookeries was heavily inspired by WordPress. And WordPress represents the best in class (in terms of ease-of-use) for traditional CMS. Traditional CMS being applications that control all the aspects of a website: pulling data that it organizes inside a database, the applying logic to manage the workflows of the data, and the creating and managing the user interface that ultimately shows the data. The traditional CMS has to do a lot of things. That usually means that the CMS developer needs to add a lot of assumptions and constraints to ship said CMS. And when those assumptions no longer hold, it takes a lot to change the codebase.

In the case of WordPress (and similar styled CMSs), the server has to do a lot of work with building a page. A WordPress site consists of both the site, and its admin console. While there has been work on updating the theme management and the page/post editor, ultimately there are limits to what kind of UIs that WordPress can support. WordPress also has a massive plugin marketplace, because the core developers do not know what every website will need. (Nor does it make sense to build everything in or every possibility.) For a modern WordPress powered site to stand-out, it needs needs a custom theme and often a half-dozen plugins. Naturally having so many moving parts, from different vendors (some theme and plugin devs are better than others) means there is a a greater chance of security issues. The routine upgrade of themes, plugins and the WordPress core is a rite that one has to diligently perform regularly.

It would be impossible for Rookeries to compete with WordPress head on, just given the number of hours I would need to sink to make things a reality. Also I do not think this desirable given the current direction.

The Alternative of Static Site Generation and API Driven Sites

The assumption that the server must handle most of the layout and display issues does not hold when dealing with modern browsers. Modern browsers can run rich multimedia experiences and real-time applications. Running intensive applications such as a 3D game is now possible, and will become come place. Ultimately the web is now a platform, a target that application developers can directly target.

As a result, many web agencies are turning to the JAMstack and having their websites act as their own full-blown applications. The applications either talk to a headless CMS acting an API or even foregoing that with static site generation. Probably the best example of this is Gatsby for generating sites built in React, which I am currently using to build out the Amber Penguin Software site. I also plan on eventually converting my other existing WordPress sites to use Gatsby or a similar tool. These tools as other web agencies found, separate out the complex logic of a frontend app from the backend and its data. These means more flexibility when building out a site. It also means that the backend CMS can be hardened and simplified to avoid many security issues. In fact with static site generation, the web app can be so removed from its CMS and database, that attacking a site becomes irrelevant. Such a site can also have better performance, and take advantage of caching and CDNs.

The Future of Rookeries

While there are a number of headless CMS and static site generators out there, I feel like the overall experience of working with them needs some improvement. There are no real good headless CMS systems written in Python or Rust, and I do think there are some really unpleasant rough edges around running a static site. Hence I plan on reworking Rookeries to help me build a CMS that can power my various sites. At the moment, this version 0.10.0 has feature parity with the previous version of Rookeries. I still need to rewrite some of the admin and testing in Rust, to avoid the need for Python. Also I need to figure out a nice manner to expose a flexible API to my sites. Fortunately I have enough examples to keep me busy for a bit.

Rookeries v0.9.0 out – New UI and Live Editing of Sites + Juggling JSON with jq Book Update

It has been quite a while since my last update. I apologize for the long silence. I wanted to focus on getting Rookeries up and running, to the degree that I can host a website. Namely I was hoping to update the Amber Penguin Software website and the Juggling JSON with jq book companion website to use Rookeries. Unfortunately I had to re-architecture the UI and bring the CouchDB management of the site and pages up to spec. However I am happy with the overall results:

Interactive Editing of Menus

Rookeries v0.9.0 introduces support for adding, removing and reordering menu items. It took a bit to find a good simple implementation of a drag and drop able list.

]4 Version 0.9.0 introduces interactive editing of menus.

Interactive Editing of Site Headers and Footers

Rookeries v0.9.0 also extends support of editing pages to site headers and footers. It uses the same inline editor for Markdown and HTML, that the pages currently enjoy.

]5 You can now edit site headers in Rookeries

So what else changed?

  • The migration of the UX over to a sliding sidebar is done.
  • Internally redux was replaced with MobX, which is far more maintainable for me.
  • The addition of saving sites and the current selected page.

There is still a lot to do on Rookeries, such as making the CMS more robust and flexible. Adding and removing pages is still outstanding. So is selection of pages via URLs. Marking whether or not changes have been made, to prompt the user to save. Also to check that the site is not in an invalid state. However things are starting to look up.

A few people have inquired about the state of the Juggling JSON with jq book, and when will a sample chapter and table of contents will be available. I apologize for not replying directly to those emails (I will do so shortly), but I hope to get those out in the next few days, and hopefully before the end of the year. Work on Rookeries has essentially ate up all the time that I would of used for working on the book. I think going forward I will work on both in parallel.

Juggling JSON with jq is Out Today

Apologies for the late post but it has been a busy day. As of today you can buy the early edition of Juggling JSON with jq on Gumroad. I am very excited since this is my first attempt at self publishing a book. Naturally the journey is still continuing as I work towards the final release of the book. All buyers of the book will get updates including the final version when it comes out.

I plan sending out an update on the book and the companion site/API that I am working on.

Getting Started with Writing a Technical ebook

The early release of my ebook Juggling JSON with jq comes out tomorrow! However this post is more about the process of writing the book itself.

Getting started on an technical ebook, (such as Juggling JSON with jq), requires a bit of upfront setup. On the ebook side, I decided to go the route of writing the book in Markdown, and generating the various formats using Sphinx. While I feel most comfortable using Markdown, and yet Sphinx uses reStructedText by default. So I had to coax Sphinx to accept Markdown by using a project called m2r. Generating the PDF version of the ebook took a bit to get working. Sphinx uses LaTeX to generate PDFs, and LaTeX while powerful can be clunky to work with. I wrapped everything up with an invoke script, and now I can quickly generating new versions of ebook in the various formats I want to support.

Something unique to writing technical books, is the need to have actual working examples. You can learn by reading, but working through exercises and examples re-enforces that learning. In the case of Unjumbling JSON with jq, I needed an example REST API that readers play with. I searched for some nice open APIs, but nothing seemed very compelling. Many of the open APIs require some form of user registration and non-trivial authentication method that would complicate the examples in the book. So I setup a simple demo API for the book. Thankfully with Docker and Flask, that isn’t a particularly daunting task. (Dockerizing most of my webapps definitely made my live easier overall.)

Finally using Gumroad made marketing and selling the book a lot more approachable. Getting everything setup for e-commerce is a daunting job, if you plan on doing it yourself. Thankfully for ebooks, and similar digital products, Gumroad solves most of the problems one can encounter. I definitely recommend using them if you are planning to do something similar.

Book Announcement: Unjumbling JSON with jq

jq is an amazing tool for querying and manipulating JSON in command-line, that I learned about from one of my good colleagues, Eric Olsen. And I feel that jq deserves a good book describing how to use this tool. Hence I am writing a book called Unjumbling JSON with jq on the topic.

As mentioned in a previous post, I originally planned on writing a single book on both jq and httpie. I divided the original book in two, because there is only a small overlap between the two. I wanted to show examples of grabbing a REST API response via httpie, and parsing the JSON output with jq. However basic querying a REST API is something that could be covered in a short section. By writing the books separately, I will be able to release them faster, and the books will be much more focused.

I plan on selling early drafts of the ebook on August 10th. Buyers of the ebook will get regular versions of the evolving drafts of the ebook, and a free upgrade to the final version of the book. I want to release the early drafts to get early reader feedback. In addition readers of the book will have access to the REST API that accompanies the book.

You can order the early version of Unjumbling JSON with jq from here].

WordPress Password Resets via MySQL

I have not completed the switch away from WordPress completely, (as this site and the justCheckers site show). I might switch to using something like Django CMS or Wagtail. Unfortunately I have not had as much time as I’d like to, to work on Rookeries, my own Flask based CMS

Still in the meantime, I managed to accidentally lock myself out of my own WordPress sites. Thankfully there are a few ways to reset passwords in WordPress. The most surefire way I found was to reset the password using MySQL. (Using the wp-cli tools looks interesting, but I didn’t feel like setting up get another PHP tool.) Most of the time you don’t need to do this. However if you’ve managed to forget your only admin password… well this will get you out of that problem. So what does resetting a WordPress password via MySQL, you ask?

  1. Log into your server via SSH (or to MySQL via a SSH tunnel if you have that enabled)
  2. Login into MySQL: mysql -u $MY_DB_USER -p
  3. Get the username if you have not already. You can look those up in the ${MY_WP_SUFFIX}_wp_users table.
  4. Finally reset the password, using the MD5() function and an update SQL statement: UPDATE "wp_users" SET "user_pass" = MD5('new_password') WHERE "wp_users"."user_login"= "username";
  5. Log in with the user using the regular WordPress login (e.g. https://my-wordpress.example.com/wp-login.php). Remember to change the password, as that will use a stronger hash than MD5 internally and is more secure.

And there you go!

Notify Me when Done “X” in KDE

One of the few Java webapps I work on at work, has a very long startup time. Unfortunately since the server startup code is proprietary and owned by the vendor, there is not much I can do about that. However it is easy to forget to check if the server has started up, I decided to that I needed a way for my computer to notify me that the webapp was up. Here is how I came up with a simple and quick way to do just that in KDE.

So my webapp has an health endpoint that can be easily queried via HTTP. With httpie the HTTP query was very easy, however to script httpie to keep querying until the result came back, meaning the server was up. At first I tried do a while with negation of the return code, and then I found on StackOverflow that the bash until command will do just that. (Without needing to figure out the appropriate negation).

The second part was figuring how to create notifications in KDE via the console. Turns out that kdialog will create both notifications and general popup alerts.

Putting the two together I came up:

until http :8080/my_health_endpoint; do echo 'Waiting...'; sleep 10; done; kdialog --passivepopup "Ready to go!" 10`

I added a sleep in there, to throttle the number of times that httpie would run. The second parameter on the kdialog dictates how long the notification popup will be around. Alternatively I could of used --msgbox if I wanted a dialog that I had to press ‘OK’ on.

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