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Discord RSS Bot, now with whales!

Angry docker avatar

Bot for taking in RSS or Atom feeds and sharing them to Discord channels, now stuffed (without grace, mind you) into a tiny container.

Introduction

This file is not intended as an introduction to Discord Feed Bot, nor as an introduction to Docker.

  • If you are unfamiliar with Discord Feed Bot, consult the ReadMe.
  • If you are unfamiliar with Docker, check out the Introduction to Docker webinar, or consult your favorite search engine.

On the other hand, this file is intended to:

  • Take your already operational Discord Feed Bot...
  • And stick it into a shoe box container so that you can hide it under your bed put it on to the back of whale/cargo ship/freight train/lorry, and never worry about it again.

Starting Out

You should already have:

  • A fully operational Discord Feed Bot, whether virtualized or bare metal. If you don't, go and learn how to do this, and then come back here.
  • Docker installed and operational on at least one node.
  • Reliable time synchronization on your docker node(s), e.g. NTP. This is a fairly common thing to already have built-in to an operating system, whether or not you're aware of it. Still, you should verify that it is functioning.
  • A copy of the Discord Feed Bot source, whether from a tarball or zip file, or a local git clone.
  • Access to your existing Discord Feed Bot configuration file, and any avatars that you have been or will be using.

Important vocabulary:

  • Docker Image: a compiled "picture" of an operating system. You build an Image.
  • Docker Container: an instance of a particular Docker Image that retains some configuration details. You run an Image to turn it into a Container.

"But I want it running now, and you mince many words!"

Ok, fine. Really can't blame you. Try:

docker build -t feedbot .
docker run -v $PWD:/home/feedbot -d feedbot

But you really, really, should not do that if you care about your sanity or security. Please read on for the right way to do it.

Build

Simply run the following command from the Discord Feed Bot source directory to build and tag your new image:

docker build -t feedbot .
docker tag feedbot feedbot:latest
docker tag feedbot feedbot:0.0.1

Assuming that it succeded, you should now have a new docker image named feedbot. Yay! Wait, why am I getting excited; it doesn't even do anything, yet! Shame on you for getting me all worked up. Tsk tsk.

For future builds, you should update the 0.0.1 version tag appropriately. This helps you if you ever want to migrate a stable image onto another node, or just want to revert back to an older image when the newest one doesn't work out as well as you had hoped.

Configure

What you likely want to do is create a new folder inside your home directory (preferably outside of the source repository, but that's not mandatory; just good practice) and copy your existing configuration file, database, and avatar(s) over to it. In other words, something like the following:

mkdir ~/dockerfeedbot
cp feed2discord.local.ini feed2discord.db ~/dockerfeedbot/
cp avatars/my_cool_avatar.png ~/dockerfeedbot/

To make it perfectly clear: Docker will not be able to access files outside of the compiled image and those contained within this folder. So just copy any needed files into your new folder, and update the configuration file (avatarfile and db_path) if you need to. It's suggested to just use the filename in your .local.ini file, with no path information, but relative paths under this folder are fine (i.e. avatarfile = avatars/bob.png when the file on-disk is at ~/dockerfeedbot/avatars/bob.png; same for db_path).

Run

To create and start the container, the following should work. Depending on your operating system, docker version, and user group/privileges, you may need to preface this command with sudo:

docker run -e TZ='UTC' -v ~/dockerfeedbot:/home/feedbot --restart on-failure:10 --name feedbot -d feedbot

To break this command down:

Command Explanation
docker run Start a new instance of a docker container.
-e TZ='UTC' Set the "system" timezone to UTC (you may want to change this, depending on a number of factors, but UTC should work best).
-v ~/dockerfeedbot:/home/feedbot Use the configuration files from ~/dockerfeedbot to mirror into the container's /home/feedbot folder.
--restart on-failure:10 Docker will automatically (re-)start feedbot, up to ten times, if any of the following occur:
  • feedbot crashes.
  • the docker daemon restarts.
  • the host reboots (on a supported operating system).
--name feedbot Name the container feedbot.
-d Run the container detached (without a console).
feedbot Construct the container from the image most recently tagged as feedbot. You can append a version number, if desired, such as feedbot:0.0.1.

You should now (hopefully) notice something similar to this in your discord window: phroggbot "Playing with containers"

Note: If you've previously run a container named feedbot, this command will fail. In that instance, you can use:

docker stop feedbot
docker rename feedbot feedbot.1

Followed by the full docker run command. If you're not interested in keeping the old docker container, and are positive that the new version is 100% successful and without issues, it's even easier:

docker stop feedbot
docker rm feedbot

Again, followed by the full docker run command.

Stop

Easy! Simply run docker stop feedbot to stop the container named feedbot.

Monitor

The Docker model for feedbot will output logging to STDOUT. This means that you can monitor a container's output with: docker logs feedbot The value set in your configuration file for debug will determine how much information is output to this log, just as if you were running it manually. To determine whether feedbot is even running, consult the output from either docker ps (to show only running containers) or docker ps -a (to show all configured containers).

Test/Debug

The testing utilities (show_all_entries.py and show_sample_entry.py) are included inside of the image we built earlier. You can access them using the following syntax:

docker run --rm feedbot show_sample_entry.py https://github.com/freiheit/discord_feedbot/releases.atom
docker run --rm feedbot show_all_entries.py https://github.com/freiheit/discord_feedbot/releases.atom
Command Explanation
docker run Start a new instance of a docker container.
--rm Delete the container once it is done executing (since it is extremely short-lived and would only waste resources).
feedbot Construct the container from the image most recently tagged as feedbot.
  • show_sample_entry.py
  • show_all_entries.py
 The command to run inside of the container.
https://github.com/freiheit/discord_feedbot/releases.atom Any parameters for the command provided above. For the included show_X.py tools, this is the URL of a feed to debug, such as the release feed for this project.

You can also directly spawn an ash shell inside of the contianer to take a peek around with the following, but this is ultimately not very useful in practice:

docker run --rm -it -e TZ='UTC' -v ~/dockerfeedbot:/home/feedbot feedbot ash

-it means run with an interactive terminal, and the rest should all be familiar to you by now.