Getting the Channels Package Installed and Configured

One of the things that's really incredible about channels 0:00 is that from the point of view of developing your Django project, 0:03 it operates just like any other pluggable Django app. 0:05 The author of channels, Andrew Godwin, worked really hard to 0:08 find abstractions that would feel familiar to Django developers, and 0:11 that would play nicely with the rest of the Django ecosystem. 0:15 Eventually, maybe even by the time you're watching this workshop, 0:18 channels will be integrated into the core of Django. 0:21 And then instead of installing it separately, 0:24 you'll just use it any time that you need it. 0:27 For now though, we still need to install channels the way that we would normally 0:29 install any other package. 0:31 So through pip or in my case through PyCharm. 0:33 Now you can check out a GitHub repository with all of the code for this workshop. 0:37 I'll have a link to that repository along with a note on how to check out 0:41 the channel's initial tag. 0:43 So you can code along with me in the teacher's note. 0:45 On your own computer you'll probably want to install Django and 0:48 channels into a virtual environment by using pip. 0:50 Since I'm using Pycharm, 0:53 however, my installation process is a little bit different. 0:54 So for me I go to the project and the project interpreter and 0:58 I click the little plus sign and I choose Django. 1:02 Now I'm in a specified version, 1.10.3. 1:06 You can use 1.10.4 or whatever version you want to use. 1:09 I'm gonna install that package. 1:14 And then I also need to install channels. 1:16 Now, you'll do this with pip install channels if you're using 1:19 a virtual environment. 1:21 I'm going to do it, again, through here, though. 1:22 And I'm going to notice that this is version 0.17.3. 1:27 I'm not gonna necessarily specify a version here because, since channels is 1:31 still in development, you probably want to use the newest one at any given time so 1:35 that you know you have the newest version of channels. 1:39 And then one thing I definitely want to remember to do, 1:42 is to add channels to my requirements .txt. 1:45 So that was 0.17.3 and I will save that. 1:50 Now we have channel installed, we need to configure our project to use it. 1:55 In the settings.py for the project, 1:59 we're going to add channels to our installed Apps. 2:02 So I'm gonna add it right here above my votes app. 2:06 And then down at the bottom of the settings file, really anywhere but 2:12 I like to add this at the bottom, we need to add a new set of settings. 2:15 And this is called CHANNEL_LAYERS. 2:21 It's a dictionary and 2:23 the default key is also a dictionary 2:26 which has two keys BACKEND and ROUTING. 2:31 So back end is gonna be set to A-S-G-I-R-E-F, 2:37 asgiref.inmemory.channellayer. 2:44 And routing is going to be set to djangocity.routing.channel routing. 2:48 Now this setting is new, you've likely never seen this before, 2:57 so it might need a little bit more explaining. 3:01 Channels operates on an event driven context. 3:03 Events can be messages that you send to your app to various pieces of channels 3:06 code or they could be client started events like HTTP requests or 3:09 WebSocket client connections. 3:13 Channels needs a way of keeping track of events and communicating events 3:15 between different pieces of code and it uses a channels layer to do so. 3:18 Think of a layer as a messenger between different pieces of code. 3:23 Channels ships with some built in layers and 3:26 the one that we're using in this setting is the in memory layer. 3:29 That layer will keep references and past messages inside of your system's memory. 3:32 This layer is fine for development but shouldn't be used in production, 3:37 because it can lead to memory leaks and degraded performance. 3:39 We'll talk about some other options for 3:42 this when we talk about deploying our channel's project. 3:44 The last piece of information we need is the channel's routing, 3:47 which is referenced by the last line in the channel layers block. 3:50 Channels routes are somewhat like Django's URL patterns, and live in a similar place. 3:53 Here in the Django City app, the directory that holds our URLs up high, 3:58 I'm going to add a new file that's named routing.py. 4:03 And yeah, go ahead and add that to version control. 4:09 Now this file is going to hold our routes. 4:13 So first I'm going to import from channels.routing the route function. 4:15 And then I'm gonna make a new list here named channel_routing, 4:23 much like we would have a list of url patterns. 4:27 So for now that's it. 4:31 That's all I need to do. 4:33 And I can run the server to make sure that things are still working. 4:34 So I can do run server and 4:41 we see that we get this busy loop synchronous mode on channel layer. 4:42 That tells us that channels are registered. 4:47 And if I refresh this page, everything still works. 4:50 So our project is now running with channels. 4:54 We're ready to start serving WebSockets clients. 4:55 In the next video will add some code to our project that will respond 4:58 when it receives WebSocket events. 5:01