Building data-driven web apps with Flask and SQLAlchemy Transcripts
Chapter: Deployment
Lecture: The setup script and config files
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Now it's time to start working with our code.
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We're in another chapter in our GitHub repo
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Chapter 15_deploy
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and of course I made a copy of the code
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we have starter and a final
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and these are actually not super different
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but there's going to be a few files that we change.
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Now, in order for us to get things to work in Linux
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what we have to do is create
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a couple of configuration files.
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We need to talk about how to run uWSGI
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which is going to run our Python code
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and how to run Nginx
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which is going to be the frontend server
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that's going to communicate through some back channels
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to uWSGI
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how are we going to set up the server, and so on.
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Watching me type that's not super interesting
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so I'm going to paste in some files
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and then we'll talk through them.
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So we now have a server chapter
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located next to pi, pi_org, and it has three files.
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It has an Nginx file
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and this is going to be our Nginx server configuration.
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We'll talk through that in a minute.
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It also has a unit file here.
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A unit file is like a background daemon or service.
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It's like a Windows service
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if you're coming from the Windows world.
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It just runs when the system starts.
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When Linux boots up
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this is just always going to run this code.
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So, this is going to have the configuration
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to run uWSGI and all the stuff
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we need to run our web app.
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We'll talk more about that, as well.
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The first thing we're going to work with
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is going through the script that we have here.
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So, this script, basically, is all the steps that you need
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to apply to the server in order to get into a nice
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working state, get all the dependencies set up
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firewalls, and some other things like that.
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So, what we're going to do is we're going through this
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step by step. Now, you mostly could run it.
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I think there's a couple of lines
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that you have to be a little bit interactive
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and also, down here
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you have to fill out your details and so on
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but, more or less, you could just run the script.
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We're not going to do that.
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We're going to talk through it piece by piece
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and you probably want to run it piece by piece, as well
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to see if anything fails, but it's all in one script here.
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So, this is going to be real helpful for us
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to get all set up.
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Now, final thing: the way that our code is written so far
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does not really make uWSGI, this one
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does not make uWSGI happy.
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The way that it imports stuff
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it tries to our project
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and it just imports the application out of the module.
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It doesn't run the module.
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So, what does that mean?
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Over here, under app.py
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we have some code that comes along
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and it says, really, down here at the bottom
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what we had before is just this
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and what it was doing, it says, If you run this file
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as we have been the whole time, then run the main.
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Otherwise, do nothing. Just import it.
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Well, uWSGI doesn't work that way.
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What it does is it's going to import this thing
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basically, import this file
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and then grab hold of this and run it with its own settings
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and that means this configure bit isn't getting called here.
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So, in particular, the blueprints and the database
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are not getting set up under uWSGI.
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So, what we can do is we can say
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If you run it like this, actually start the program
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start the server, the dev server.
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Otherwise, just configure it.
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So, this little tweak that I added here is necessary
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for running our code under uWSGI.
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There's other ways, as well, but this is how we're doing it.
