Python for .NET Developers Transcripts
Chapter: Deploying Python web apps
Lecture: Running in a production WSGI server
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0:00
We saw this admonishment here and you should run this in a production WSGI server instead. Yes, yes we should.
0:07
We should also turn debug mode off, which we can also do. So we're going to do this and that brings us over to a new set of files.
0:17
We've got this Nginx, we got this service file. This one controls uWSGI and it's going to run as a system daemon in the background.
0:25
Think Windows service, auto start. It's sometimes hard to see the errors and where they went. They're going to be logged over to here, which is cool
0:35
but what we want to do, is we want to just test this command without the log bit first. So let's go. It's resisting scrolling.
0:48
Now also, it says we want to use this WSGI app. We haven't defined this yet so let me go ahead and put that in here.
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Put a file called wsgi, you can call it whatever you want. This is kind of a bit of a convention. It will say from Guitary, not app. Import app.
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Now, the way that the production servers work is they don't just run your code. So remember, the way we got it was that we ran
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our code and it called this function, which called main. We can turn this to false. Right, it ran this 'cause we ran this file
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so it's kind of the startup for that file. It doesn't work that way. It just defines these pieces and it imports app.
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And then it uses that directly, okay. Actually, then I guess this doesn't matter down here, does it? If there's any additional setup, like
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let's look over here real quick. Notice this one. In main we're setting up the global INET and we're creating the tables and we're loading the data
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and we're calling run. What we would really need to do, and let me make a function over here, method. And I'll call this configure.
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So, in this case what we call main I'm going to actually run main. But if they don't do main we need to do something else.
2:05
So we can go in and say, else is the production case. So you still got to do this configure bit. Put it like that. Here we go.
2:14
Okay, so just in case you run the other one you're going to run into problems running uWSGI without this. But this world, we're not doing extra stuff.
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We haven't gotten there yet, so there's not really anything we have to do. This is good, but you would do something like possibly run
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the configure here, or just let it get called the way it was. Let's go in add.
2:48
All right, here we go. Here's our WSGI. We should be able to just run this. So, it's really good to test though.
2:57
Test this directly, 'cause it's annoying to go and always check the log file if something doesn't work. It's much easier to run it, see if this works
3:04
and then diagnose the other issues. So, when you're doing this stuff I recommend small steps at a time, okay.
3:10
So, let's run this over here and see where we get. Over in uWSGI, tell it it's using this virtual environment.
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It's running in master mode with four subprocesses. That's like the supervisor and then subprocess worker processes, each get two threads.
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Let's then import 5,000. Okay, think we're good. Woohoo, it looks like it works. Let's see, WSGI app added. All right, it seems like it works.
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Sometimes you'll see some errors come through but I don't see any this time. Must have done it right. Okay, let's try this again. Here it is.
3:49
Look at that. First time we got it working. So, as we make requests here we could do slash guitars. We can do a redirect. No, just a 200.
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Could do tar slash all. That'd give us all of our guitars back. Here you can see the electric wood grain. So, it looks like it's working.
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But we have uWSGI theoretically potentially, maybe working. That's not quite enough though. Remember, I just ran it, I ran this command.
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I didn't set it up to start when the server turns on and stop when the server shuts down. So, that's the next thing that we need to do
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is how are we going to set that up? But of course, now if I try again error. No connection. So, to accomplish that what we need to do is copy this file
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and it looks like everything's good. This is not right, this'd be a Guitary. You never create this file from scratch.
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You always get it from somewhere else. For you guys you can get it from this course. Okay, so what we want to do is we want to get this
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and we want to copy it. Let me just go ahead and put the fixed description. Not that it really matters but have it working right.
5:00
So, to make this do its magic we have to copy that file, which lives here, into etcetera. Systemd, system Guitary service.
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And then we can control it by saying, "Start Guitary" "Stop Guitary" and so on. So, it would git pull. Got our updated service and then we, whoops
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did not copy enough, did I? Want to do this copy, fingers crossed. No, got the path wrong, didn't I? Didn't I, 'cause that is not the right name.
5:38
Here we go. Let's try again with this new one. Right, no output. That means it works. Hasn't quite been started yet, so we have to say, "Start"
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and see what that does. Ooh, no errors, that's good. We can say, "Status". Alright, looks like it's running and that's cool.
5:58
We could run valances and see if it really is running. Oh yeah, there it is, it's running. And then we could do HTTP against it.
6:07
Yeah, look at that, it's running. However, if we restart the server, it's going to go away. That's not amazing.
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So we have to say, "Enable" and this will tell it basically now it's an auto starting service. It's going to start, based on the various signals
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that we put in the file. So, over here you can see after. It's just logged that target. After the system log is available.
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Yeah, this is up and running. It's great and if it crashes it'll auto start itself and so on, so pretty excellent.
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One other thing we can do is we can come over here. Go look at that. All right, there's this uWSGI log. That's cool.
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We can even say tail -f for follow -n 20. This, if we go to the other. Then we go make that request again. Now you see, here's all the output.
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Live, go in to log file. So, this is great when you're working on it you can fire this up, put it off to the side and then as you interact with
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it exceptions will show up here. Requests will show up here. All that sort of good stuff. Our systemd unit file this dot service file let us set uWSGI
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the worker process and the overseeing supervisor process for them to run and auto start when our system just boots up. That looks like progress to me.