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0x1A-application_server

README.md

0x1A. Application server

DevOps SysAdmin

c7d1ed0a2e10d1b4e9b3

Background Context

Your web infrastructure is already serving web pages via Nginx that you installed in your first web stack project. While a web server can also serve dynamic content, this task is usually given to an application server. In this project you will add this piece to your infrastructure, plug it to your Nginx and make is serve your Airbnb clone project.

Resources

Read or watch:

Requirements

General

  • A README.md file, at the root of the folder of the project, is mandatory
  • Everything Python-related must be done using python3
  • All config files must have comments

Bash Scripts

  • All your files will be interpreted on Ubuntu 16.04 LTS
  • All your files should end with a new line
  • All your Bash script files must be executable
  • Your Bash script must pass Shellcheck (version 0.3.7-5~ubuntu16.04.1 via apt-get) without any error
  • The first line of all your Bash scripts should be exactly #!/usr/bin/env bash
  • The second line of all your Bash scripts should be a comment explaining what is the script doing

Tasks

0. Set up development with Python

Let’s serve what you built for AirBnB clone v2 - Web framework on web-01. This task is an exercise in setting up your development environment, which is used for testing and debugging your code before deploying it to production.

Requirements:

  • Make sure that task #3 of your SSH project is completed for web-01. The checker will connect to your servers.
  • Install the net-tools package on your server: sudo apt install -y net-tools
  • Git clone your AirBnB_clone_v2 on your web-01 server.
  • Configure the file web_flask/0-hello_route.py to serve its content from the route /airbnb-onepage/ on port 5000.
  • Your Flask application object must be named app (This will allow us to run and check your code). Example:
Window 1:
ubuntu@229-web-01:~/AirBnB_clone_v2$ python3 -m web_flask.0-hello_route
 * Serving Flask app "0-hello_route" (lazy loading)
 * Environment: production
   WARNING: Do not use the development server in a production environment.
   Use a production WSGI server instead.
 * Debug mode: off
 * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
35.231.193.217 - - [02/May/2019 22:19:42] "GET /airbnb-onepage/ HTTP/1.1" 200 -
Window 2:
ubuntu@229-web-01:~/AirBnB_clone_v2$ curl 127.0.0.1:5000/airbnb-onepage/
Hello HBNB!ubuntu@229-web-01:~/AirBnB_clone_v2$

1. Set up production with Gunicorn

Now that you have your development environment set up, let’s get your production application server set up with Gunicorn on web-01, port 5000. You’ll need to install Gunicorn and any libraries required by your application. Your Flask application object will serve as a WSGI entry point into your application. This will be your production environment. As you can see we want the production and development of your application to use the same port, so the conditions for serving your dynamic content are the same in both environments.

Requirements:

  • Install Gunicorn and any other libraries required by your application.
  • The Flask application object should be called app. (This will allow us to run and check your code)
  • You will serve the same content from the same route as in the previous task. You can verify that it’s working by binding a Gunicorn instance to localhost listening on port 5000 with your application object as the entry point.
  • In order to check your code, the checker will bind a Gunicorn instance to port 6000, so make sure nothing is listening on that port.

Example:

Terminal 1:
ubuntu@229-web-01:~/AirBnB_clone_v2$ gunicorn --bind 0.0.0.0:5000 web_flask.0-hello_route:app
[2019-05-03 20:47:20 +0000] [3595] [INFO] Starting gunicorn 19.9.0
[2019-05-03 20:47:20 +0000] [3595] [INFO] Listening at: http://0.0.0.0:5000 (3595)
[2019-05-03 20:47:20 +0000] [3595] [INFO] Using worker: sync
[2019-05-03 20:47:20 +0000] [3598] [INFO] Booting worker with pid: 3598
Terminal 2:
ubuntu@229-web-01:~$ curl 127.0.0.1:5000/airbnb-onepage/
Hello HBNB!ubuntu@229-web-01:~$

2. Serve a page with Nginx

Building on your work in the previous tasks, configure Nginx to serve your page from the route /airbnb-onepage/

Requirements:

  • Nginx must serve this page both locally and on its public IP on port 80.
  • Nginx should proxy requests to the process listening on port 5000.
  • Include your Nginx config file as 2-app_server-nginx_config.

Notes:

  • In order to test this you’ll have to spin up either your production or development application server (listening on port 5000)
  • In an actual production environment the application server will be configured to start upon startup in a system initialization script. This will be covered in the advanced tasks.
  • You will probably need to reboot your server (by using the command $ sudo reboot) to have Nginx publicly accessible

Example:

On my server:

Window 1:

ubuntu@229-web-01:~/AirBnB_clone_v2$ gunicorn --bind 0.0.0.0:5000 web_flask.0-hello_route:app
[2019-05-06 20:43:57 +0000] [14026] [INFO] Starting gunicorn 19.9.0
[2019-05-06 20:43:57 +0000] [14026] [INFO] Listening at: http://0.0.0.0:5000 (14026)
[2019-05-06 20:43:57 +0000] [14026] [INFO] Using worker: sync
[2019-05-06 20:43:57 +0000] [14029] [INFO] Booting worker with pid: 14029

Window 2:

ubuntu@229-web-01:~/AirBnB_clone_v2$ curl 127.0.0.1/airbnb-onepage/
Hello HBNB!ubuntu@229-web-01:~/AirBnB_clone_v2$

On my local terminal:

vagrant@ubuntu-xenial:~$ curl -sI 35.231.193.217/airbnb-onepage/
HTTP/1.1 200 OK
Server: nginx/1.10.3 (Ubuntu)
Date: Mon, 06 May 2019 20:44:55 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 11
Connection: keep-alive
X-Served-By: 229-web-01

vagrant@ubuntu-xenial:~$ curl 35.231.193.217/airbnb-onepage/
Hello HBNB!vagrant@ubuntu-xenial:~$

3. Add a route with query parameters

Building on what you did in the previous tasks, let’s expand our web application by adding another service for Gunicorn to handle. In AirBnB_clone_v2/web_flask/6-number_odd_or_even, the route /number_odd_or_even/<int:n> should already be defined to render a page telling you whether an integer is odd or even. You’ll need to configure Nginx to proxy HTTP requests to the route /airbnb-dynamic/number_odd_or_even/(any integer) to a Gunicorn instance listening on port 5001. The key to this exercise is getting Nginx configured to proxy requests to processes listening on two different ports. You are not expected to keep your application server processes running. If you want to know how to run multiple instances of Gunicorn without having multiple terminals open, see tips below.

Requirements:

  • Nginx must serve this page both locally and on its public IP on port 80.
  • Nginx should proxy requests to the route /airbnb-dynamic/number_odd_or_even/(any integer) the process listening on port 5001.
  • Include your Nginx config file as 3-app_server-nginx_config.

Tips:

  • Check out these articles/docs for clues on how to configure Nginx: Understanding Nginx Server and Location Block Selection Algorithms, Understanding Nginx Location Blocks Rewrite Rules, Nginx Reverse Proxy.
  • In order to spin up a Gunicorn instance as a detached process you can use the terminal multiplexer utility tmux. Enter the command tmux new-session -d 'gunicorn --bind 0.0.0.0:5001 web_flask.6-number_odd_or_even:app' and if successful you should see no output to the screen. You can verify that the process has been created by running pgrep gunicorn to see its PID. Once you’re ready to end the process you can either run tmux a to reattach to the processes, or you can run kill <PID> to terminate the background process by ID.

Example:

Terminal 1:

ubuntu@229-web-01:~/AirBnB_clone_v2$ tmux new-session -d 'gunicorn --bind 0.0.0.0:5000 web_flask.0-hello_route:app'
ubuntu@229-web-01:~/AirBnB_clone_v2$ pgrep gunicorn
1661
1665
ubuntu@229-web-01:~/AirBnB_clone_v2$ tmux new-session -d 'gunicorn --bind 0.0.0.0:5001 web_flask.6-number_odd_or_even:app'
ubuntu@229-web-01:~/AirBnB_clone_v2$ pgrep gunicorn
1661
1665
1684
1688

ubuntu@229-web-01:~/AirBnB_clone_v2$ curl 127.0.0.1:5000/airbnb-onepage/
Hello HBNB!ubuntu@229-web-01:~/AirBnB_clone_v2$

ubuntu@229-web-01:~/AirBnB_clone_v2$ curl 127.0.0.1:5001/number_odd_or_even/6
<!DOCTYPE html>
<HTML lang="en">
  <HEAD>
    <TITLE>HBNB</TITLE>
  </HEAD>
  <BODY><H1>Number: 6 is even</H1></BODY>
</HTML>ubuntu@229-web-01:~/AirBnB_clone_v2
ubuntu@229-web-01:~$ 
ubuntu@229-web-01:~/AirBnB_clone_v2$ curl 127.0.0.1/airbnb-dynamic/number_odd_or_even/5
<!DOCTYPE html>
<HTML lang="en">
  <HEAD>
    <TITLE>HBNB</TITLE>
  </HEAD>
  <BODY><H1>Number: 5 is odd</H1></BODY>
</HTML>ubuntu@229-web-01:~/AirBnB_clone_v2$

Local machine:

vagrant@ubuntu-xenial:~$ curl 35.231.193.217/airbnb-dynamic/number_odd_or_even/6<!DOCTYPE html>
<HTML lang="en">
  <HEAD>
    <TITLE>HBNB</TITLE>
  </HEAD>
  <BODY><H1>Number: 6 is even</H1></BODY>
</HTML>vagrant@ubuntu-xenial:~$

4. Let's do this for your API

Let’s serve what you built for AirBnB clone v3 - RESTful API on web-01.

Requirements:

  • Git clone your AirBnB_clone_v3
  • Setup Nginx so that the route /api/ points to a Gunicorn instance listening on port 5002
  • Nginx must serve this page both locally and on its public IP on port 80
  • To test your setup you should bind Gunicorn to api/v1/app.py
  • It may be helpful to import your data (and environment variables) from this project
  • Upload your Nginx config file as 4-app_server-nginx_config

Example:

Terminal 1:

ubuntu@229-web-01:~/AirBnB_clone_v3$ tmux new-session -d 'gunicorn --bind 0.0.0.0:5002 api.v1.app:app'
ubuntu@229-web-01:~/AirBnB_clone_v3$ curl 127.0.0.1:5002/api/v1/states
[{"__class__":"State","created_at":"2019-05-10T00:39:27.032802","id":"7512f664-4951-4231-8de9-b18d940cc912","name":"California","updated_at":"2019-05-10T00:39:27.032965"},{"__class__":"State","created_at":"2019-05-10T00:39:36.021219","id":"b25625c8-8a7a-4c1f-8afc-257bf9f76bc8","name":"Arizona","updated_at":"2019-05-10T00:39:36.021281"}]
ubuntu@229-web-01:~/AirBnB_clone_v3$
ubuntu@229-web-01:~/AirBnB_clone_v3$ curl 127.0.0.1/api/v1/states
[{"__class__":"State","created_at":"2019-05-10T00:39:27.032802","id":"7512f664-4951-4231-8de9-b18d940cc912","name":"California","updated_at":"2019-05-10T00:39:27.032965"},{"__class__":"State","created_at":"2019-05-10T00:39:36.021219","id":"b25625c8-8a7a-4c1f-8afc-257bf9f76bc8","name":"Arizona","updated_at":"2019-05-10T00:39:36.021281"}]
ubuntu@229-web-01:~/AirBnB_clone_v3$

Local Terminal

vagrant@ubuntu-xenial:~$ curl 35.231.193.217/api/v1/states
[{"__class__":"State","created_at":"2019-05-10T00:39:27.032802","id":"7512f664-4951-4231-8de9-b18d940cc912","name":"California","updated_at":"2019-05-10T00:39:27.032965"},{"__class__":"State","created_at":"2019-05-10T00:39:36.021219","id":"b25625c8-8a7a-4c1f-8afc-257bf9f76bc8","name":"Arizona","updated_at":"2019-05-10T00:39:36.021281"}]
vagrant@ubuntu-xenial:~$

5. Serve your AirBnB clone

Let’s serve what you built for AirBnB clone - Web dynamic on web-01.

Requirements:

  • Git clone your AirBnB_clone_v4
  • Your Gunicorn instance should serve content from web_dynamic/2-hbnb.py on port 5003
  • Setup Nginx so that the route / points to your Gunicorn instance
  • Setup Nginx so that it properly serves the static assets found in web_dynamic/static/ (this is essential for your page to render properly)
  • For your website to be fully functional, you will need to reconfigure web_dynamic/static/scripts/2-hbnb.js to the correct IP
  • Nginx must serve this page both locally and on its public IP and port 5003
  • Make sure to pull up your Developer Tools on your favorite browser to verify that you have no errors
  • Upload your Nginx config as 5-app_server-nginx_config

After loading, your website should look like this:

7a8a7c33021b1b74f9cdc1fd8f855bdb1f8cd44e

Screenshot from 2023-08-14 23-29-58

Screenshot from 2023-08-14 23-29-33

Screenshot from 2023-08-14 23-29-23

6. Deploy it!

Once you’ve got your application server configured, you want to set it up to run by default when Linux is booted. This way when your server inevitably requires downtime (you have to shut it down or restart it for one reason or another), your Gunicorn process(es) will start up as part of the system initialization process, freeing you from having to manually restart them. For this we will use systemd. You can read more about systemd in the documentation posted at the top of this project but to put it succinctly, it is a system initialization daemon for the Linux OS (amongst other things). For this task you will write a systemd script which will start your application server for you. As mentioned in the video at the top of the project, you do not need to create a Unix socket to bind the process to.

Requirements:

  • Write a systemd script which starts a Gunicorn process to serve the same content as the previous task (web_dynamic/2-hbnb.py)
  • The Gunicorn process should spawn 3 worker processes
  • The process should log errors in /tmp/airbnb-error.log
  • The process should log access in /tmp/airbnb-access.log
  • The process should be bound to port 5003
  • Your systemd script should be stored in the appropriate directory on web-01
  • Make sure that you start the systemd service and leave it running
  • Upload gunicorn.service to GitHub
bob@dylan:~$ curl -s 127.0.0.1:5003/2-hbnb | tail -5
    </div>
    <footer>
      <p>Holberton School</p>
    </footer>
  </body>
</html>
bob@dylan:~$ 
bob@dylan:~$ curl -s 12.13.14.15/ | tail -5
    </div>
    <footer>
      <p>Holberton School</p>
    </footer>
  </body>
</html>
bob@dylan:~$

7. No service interruption

One of the most important metrics for any Internet-based business is its uptime. It is the percentage of the time over a given period that the service/product is accessible to customers. Let’s pick the example of Amazon.com, for every minute of downtime (which is the opposite of uptime), it costs the company $2M. Yet, application servers often need to restart to update with the new version of the code or new configuration, when doing this operation, an application server cannot serve traffic, which meant downtime.

To avoid this; application servers are designed with a master/workers infrastructure. The master is in charge of:

  • Receiving requests
  • Managing workers (starting, stopping)
  • Distributing requests to workers

Workers are the actual ones processing the query by generation dynamic content by processing the application code.

To update an application without downtime, the master will proceed with a progressive rollout of the update. It will gracefully shut down some workers ( meaning that it will tell workers to finish processing the request they are working on, but will not send them new requests, once the worker is done, it’s will be shutdown) and start new ones with the new application code or configuration, then move on to the other old workers until it has renewed the whole pool.

Write a simple Bash script to reload Gunicorn in a graceful way.

Example:

sylvain@ubuntu$ ps auxf | grep gunicorn
vagrant   9376  2.2  3.6  58068 18320 pts/3    S+   19:25   0:00  |   \_ /home/vagrant/AirBnB_clone_v4/bin/python3 /home/vagrant/AirBnB_clone_v4/bin/gunicorn --bind 0.0.0.0:8001 --workers 4 web_flask.0-hello_route:app
vagrant   9379  2.6  4.6  82800 23116 pts/3    S+   19:25   0:00  |       \_ /home/vagrant/AirBnB_clone_v4/bin/python3 /home/vagrant/AirBnB_clone_v4/bin/gunicorn --bind 0.0.0.0:8001 --workers 4 web_flask.0-hello_route:app
vagrant   9380  2.6  4.6  82804 23120 pts/3    S+   19:25   0:00  |       \_ /home/vagrant/AirBnB_clone_v4/bin/python3 /home/vagrant/AirBnB_clone_v4/bin/gunicorn --bind 0.0.0.0:8001 --workers 4 web_flask.0-hello_route:app
vagrant   9381  2.4  4.6  82808 23128 pts/3    S+   19:25   0:00  |       \_ /home/vagrant/AirBnB_clone_v4/bin/python3 /home/vagrant/AirBnB_clone_v4/bin/gunicorn --bind 0.0.0.0:8001 --workers 4 web_flask.0-hello_route:app
vagrant   9383  2.4  4.6  82816 23136 pts/3    S+   19:25   0:00  |       \_ /home/vagrant/AirBnB_clone_v4/bin/python3 /home/vagrant/AirBnB_clone_v4/bin/gunicorn --bind 0.0.0.0:8001 --workers 4 web_flask.0-hello_route:app
vagrant   9388  0.0  0.1  10460   940 pts/2    S+   19:25   0:00      \_ grep --color=auto gunicorn
sylvain@ubuntu$ ./4-reload_gunicorn_no_downtime
sylvain@ubuntu$ ps auxf | grep gunicorn
vagrant   9376  1.0  3.6  58068 18368 pts/3    S+   19:25   0:00  |   \_ /home/vagrant/AirBnB_clone_v4/bin/python3 /home/vagrant/AirBnB_clone_v4/bin/gunicorn --bind 0.0.0.0:8001 --workers 4 web_flask.0-hello_route:app
vagrant   9393  6.5  4.6  82832 23168 pts/3    S+   19:25   0:00  |       \_ /home/vagrant/AirBnB_clone_v4/bin/python3 /home/vagrant/AirBnB_clone_v4/bin/gunicorn --bind 0.0.0.0:8001 --workers 4 web_flask.0-hello_route:app
vagrant   9394  6.5  4.6  82832 23172 pts/3    S+   19:25   0:00  |       \_ /home/vagrant/AirBnB_clone_v4/bin/python3 /home/vagrant/AirBnB_clone_v4/bin/gunicorn --bind 0.0.0.0:8001 --workers 4 web_flask.0-hello_route:app
vagrant   9395  6.0  4.6  82840 23180 pts/3    S+   19:25   0:00  |       \_ /home/vagrant/AirBnB_clone_v4/bin/python3 /home/vagrant/AirBnB_clone_v4/bin/gunicorn --bind 0.0.0.0:8001 --workers 4 web_flask.0-hello_route:app
vagrant   9396  7.0  4.6  82844 23188 pts/3    S+   19:25   0:00  |       \_ /home/vagrant/AirBnB_clone_v4/bin/python3 /home/vagrant/AirBnB_clone_v4/bin/gunicorn --bind 0.0.0.0:8001 --workers 4 web_flask.0-hello_route:app
vagrant   9402  0.0  0.1  10460   936 pts/2    S+   19:25   0:00      \_ grep --color=auto gunicorn
sylvain@ubuntu$

In this example, you can see that my Bash script tells the master Gunicorn renewed all the workers.

For testing it, please use the command $ sudo reboot to reboot your server (not shutdown!!)