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Hi guys and welcome back.
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In this video we're going to be configuring uWSGI
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so that it can run our application
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when engine x talks to it.
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Remember that we can run our app directly
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using Flask and Python.
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However, that doesn't perform as well
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and it's not as safe as using another server
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that is placed in front of it.
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By using engine x to talk to uWSGI
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and uWSGI to talk to our app
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we're going into create higher performance
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and more security.
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Let's begin by modifying our uWSGI.ini file.
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Notice that we've already got some stuff here
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but this is for Heroku,
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so we need to make a couple of changes.
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I'm going to delete all of these lines
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by just pressing D D twice for each line.
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Don't delete the uWSGI line there
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because that tells the running programme
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that these files is about uWSGI.
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We're going to need a bunch of things.
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First of all, the base.
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This is where the home folder of our application is,
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and that's in var/www/html/pricing-service.
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Then we do tell it, which file contains our app.
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So that's app.py and the .py is inferred
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so you don't have to give it.
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Then which module, we should import
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in order to include our app.
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And that is also the app module.
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And here we're using the %[]
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just to refer to this variable here.
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You could just do app,
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but if we want to change the app file later on,
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we just have to change it in one place
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as opposed to in two places.
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So this is why we're doing that.
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Next up, we need to tell uWSGI,
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where our virtual environment is located.
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So for that, we need to first find it,
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I'm going to press escape and :wq to save and quit.
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And then I'm going to run pipenv --venv.
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And this tells me where the virtual environment is located.
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Just copy all of that,
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making sure not to miss any characters,
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and then go back to uWSGI.
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Notice I'm pressing the up arrow in my keyboard
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to cycle through old commands just for speed.
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Go back in here and press the I key
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to go into insert mode again,
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and type home equal your path.
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Then we need to also set the Python path,
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and this is going to be our base folder.
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When we type home,
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this sets where Python is located in our system,
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as well as where any libraries
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we may want to import should be looked for, at first.
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The Python path defines where
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the top level of our application is.
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So that when we import any local files,
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we will look there first.
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We need to define a socket,
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and this is just a file that contains some information
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so that engine x can talk to uWSGI.
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And we just need to define
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where this file will be created by uWSGI
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so that engine x can then find it.
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And I'm going to create it in the base folder/socket.sock.
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These are normally called .sock files
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I would keep it as that.
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We need to make sure that this socket can be read
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and written to by anybody, including the engine x users.
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So I'm going to do chmod-socket equal 777
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And this allows everybody
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to read and write that socket file.
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If you don't fully understand what these commands are doing,
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don't worry too much,
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That is a bit of research that goes into creating these,
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and you don't really have to know all that much about it.
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Then we're gonna create a certain number of processes,
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which I'm going to stick to eight and threads, eight.
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eight threads and eight processes mean a total of 64
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independent instances running of our application,
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which means that we can serve more users at once.
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However, the more processes and threads you have,
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the less resources each one has, by your application.
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That means that they go slower, the more you have.
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This is a trial and error number.
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So you have to find out what number of processes and threads
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is good for your server,
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and just play around with it until you find a good number.
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By checking the performance of your application,
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how many users can interact with it at once and so on.
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There is a whole field of software testing
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called load testing, that we're not going to get into here.
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But for now, I've seen the eight processes and eight threads
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seems to perform all right.
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After we're going to define the harakiri variable,
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and this is how many seconds we will wait
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before killing one of these threads, if there is an error.
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For example, it's possible the thread may recover
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so we're giving it 15 seconds
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before we kill it and restart it.
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Killing and restarting a thread can be quite damaging
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because it can cause shutdowns for your users,
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connection errors and things like that.
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So we do want to give it a little bit of time
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to recover if it can.
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Then we've got our callable, and that is the app as well.
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And finally, where we're going to log to,
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and that's going to be in the base/log/%n.log.
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This is just going to create a file called uWSGI.log
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and is going to write our applications output
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and any other Python output into it.
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If we do have any application errors,
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we will be checking uWSGI.log inside the log folder.
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That's everything we need in this file
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so call on wq after pressing escape,
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and we are good to go with our uWSGI.ini.
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The next thing we have to do is create a system daemon
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that will take care of starting up uWSGI for us.
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So we're going to do
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sudo vi /etc/systemd/system
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/uwsgi_pricing_service.service.
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This is a new file, and we're gonna go into insert mode.
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And then we're gonna write a bunch of things.
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First, we're gonna start with a unit section.
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And this just describes what we're doing here
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so that when it appears in the logs,
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we will be able to identify them more easily.
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So we will put a description
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and this is gonna be uWSGI Pricing Service.
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Then we will go into the service configuration itself.
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So any information that we provide here,
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will be used to run this service, which runs uWSGI.
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So we'll say that the user that is running this service
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is the Jose user and the group is also Jose,
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then we're going to say that the working directory
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which is where this thing that we're running is located
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is in var/www/html/pricing-service.
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Then we will define an environment variable,
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which is our MONGODB_URI
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and that is going to be
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monogodb://127.0.0.1:27017
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/fullstack.
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Then we will define the command that actually starts uWSGI.
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So ExecStart, and this command is going to be
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/home/jose/.local
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/bin/pipenv.
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This is the absolute path to our pipenv installation
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that we have in this system.
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Then we're going to type run uwsgi.
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And what this is going to do,
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it's just going to launch pipenv
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inside this pricing service folder.
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And it's gonna call pipenv with these arguments
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run uwsgi, and that's gonna start up
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the uWSGI binary inside our virtual environment.
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Then you want to type --master --emperor
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and we're gonna define the configuration file for uWSGI
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which is uwsgi.ini.
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Then we're gonna say --die-on-term
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which is when we terminate uWSGI,
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which should kill the process.
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-uid is going to be Jose
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and --gid is going to be Jose as well.
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And finally, a --logto wear any Emperor logs
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are going to be forwarded to.
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And that's gonna be /var/www
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Oh sorry, I actually don't need that.
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That's just going to be log/emperor.log.
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So what is emperor and what is uWSGI.
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uWSGI is the main programme that we talked to our Python app.
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And the emperor is sort of like a manager for it,
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that will manage the different threads and processes
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and kill them if they fail and restart them and so on.
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So we're gonna have two different log files,
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the uwsgi.log
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that contains our application, logs and things like that.
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And we're going to have emperor.log
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which contains the manager's logs.
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Things like if there's a failure to start up
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and things like that could end up in emperor.log
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Then we're going to type to Restart = always
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KillSignal is SIGQUIT
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Type is notify,
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NotifyAccess is all
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and then a new section for instal is gonna be
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WantedBy = muliti-user.target
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A bunch of these things you don't have to worry about again,
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they are things like, who should have access
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to run this service,
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when should the service start if the server restarts,
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and things like that.
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Now that we've got this we can press escape
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call on wq for write and quit.
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And there is just one more thing we have to do
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in case we haven't done it already,
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which is that we have to do
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touch log/emperor.log
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We just have to create the emperor.log file
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because if not the root user will create it for us
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and it won't have permissions for our user to write to it.
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Now that we've got all this,
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we have to do a couple of things.
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The first one is that we're gonna do
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sudo systemctl daemon-reload
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And that is just going to reload all the system daemons
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and system services that we have created.
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We've just created one for now.
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Then we're going to do
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sudo systemctl start uwsgi_pricing_service
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Hopefully, that's what happens, absolutely nothing.
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But if you do get an error, ask away in the course Q&A
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we'll be more than happy to help you out.
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But the likely thing is that there's been a typo somewhere.
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So please do double check the two files
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that we've written so far.
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The uwsgi.ini and the uwsgi_pricing_service.service.
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The next thing to check
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is the log/uwsgi.log
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So what you should see here
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is if you go down to the very bottom of the file,
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you should see these things.
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Spawned uWSGI worker 1 2 3 4 5 6 7 8, so on.
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What this says
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is that you've got your eight processes there.
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If you see any sort of error, or anything like that,
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again, ask away in the course Q&A
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or search in Google stack overflow
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sometimes has a bunch of nice things around this as well.
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But hopefully, everything's worked up to now.
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And we are ready to set up engine x to talk to uWSGI,
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which will talk to our app.
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And those three together are what's going
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to serve our users with their content.
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I'll see you in the next video.