Session-08.txt

DB --> Stateful --> state/DB --> it should be stored
API --> CRUD on DB --> stateless applications
Web --> fetching data from API tier --> stateless applications

WEB/API Tier
---------------
1. Developers use programming languages to develop
2. We should compile
3. We should build and package it
4. We store packages .zip, .jar, etc in some location. like nexus, s3, etc.
5. We will fetch the package and deploy inside the server.

Deploy
-------------
1. Create server
2. Install language
3. fetch the package and install dependencies
4. create a service
5. do some configuration

1. Install
2. Configure
3. Run


DB tier --> heavy applications --> t3.micro
APP/WEB tier --> t2.micro

MongoDb server --> Linux server is local to --> by default it expects the application should be running in same server...

systemd service
--------------------
[Unit]
Description=The nginx HTTP and reverse proxy server
After=network.target remote-fs.target nss-lookup.target

[Service]
Type=forking
PIDFile=/run/nginx.pid
# Nginx will fail to start if /run/nginx.pid already exists but has the wrong
# SELinux context. This might happen when running `nginx -t` from the cmdline.
# https://bugzilla.redhat.com/show_bug.cgi?id=1268621
ExecStartPre=/usr/bin/rm -f /run/nginx.pid
ExecStartPre=/usr/sbin/nginx -t
ExecStart=/usr/sbin/nginx
ExecReload=/bin/kill -s HUP $MAINPID
KillSignal=SIGQUIT
TimeoutStopSec=5
KillMode=mixed
PrivateTmp=true

[Install]
WantedBy=multi-user.target


/etc/systemd/system/ --> Linux looks for the services when it is starting


we create a service in /etc/systemd/system/ folder to manage it as native systemctl service.


[Unit]
Description = Catalogue Service

[Service]
User=roboshop
Environment=MONGO=true
Environment=MONGO_URL="mongodb://172.31.2.4:27017/catalogue"
ExecStart=/bin/node /app/server.js
SyslogIdentifier=catalogue

[Install]
WantedBy=multi-user.target

load some products into mongodb

admin application --> support team

Admin UI
--------------
Enter Product Name _____________
Enter Product Code ______________
Enter Price _______________

1. Install mongodb client software inside catalogue
2. Connect to mongodb server
3. developer gave us some initial products
4. load them into mongodb.

mongodb-org-shell --> mongo client

mongodb-org --> mongodb server

mongo --host 172.31.2.4 < /app/schema/catalogue.js

< --> input
> --> output/redirection


proxy_http_version 1.1;
location /images/ {
  expires 5s;
  root   /usr/share/nginx/html;
  try_files $uri /images/placeholder.jpg;
}
location /api/catalogue/ { proxy_pass http://172.31.2.59:8080/; }
location /api/user/ { proxy_pass http://localhost:8080/; }
location /api/cart/ { proxy_pass http://localhost:8080/; }
location /api/shipping/ { proxy_pass http://localhost:8080/; }
location /api/payment/ { proxy_pass http://localhost:8080/; }

location /health {
  stub_status on;
  access_log off;
}

less /var/log/messages

Shift+g --> down
gg --> take up
q --> quit

tail -f <log-file>

http://3.236.137.205/api/catalogue/product/HAL-1

Request: /product/HAL-1

2** --> sucess
3** --> redirection

4** --> client side error, you are not giving proper URL

5** --> server side error, there is something wrong inside server/code


Aug 10 02:33:04 ip-172-31-2-59 catalogue[17029]: {"level":"info","time":1691634784669,"pid":17029,"hostname":"ip-172-31-2-59.ec2.internal","req":{"id":15,"method":"GET","url":"/product/HAL-1","headers":{"host":"172.31.2.59:8080","connection":"close","accept":"application/json, text/plain, */*","user-agent":"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/115.0.0.0 Safari/537.36","referer":"http://3.236.137.205/product/HAL-1","accept-encoding":"gzip, deflate","accept-language":"en-US,en;q=0.9","if-none-match":"W/\"aa-xQNHqR5jhJZvexZ2H1Mr7Tu9hyg\""},"remoteAddress":"::ffff:172.31.9.45","remotePort":59284},"res":{"statusCode":304,"headers":{"x-powered-by":"Express","timing-allow-origin":"*","access-control-allow-origin":"*","etag":"W/\"aa-xQNHqR5jhJZvexZ2H1Mr7Tu9hyg\""}},"responseTime":3,"msg":"request completed","v":1}

RHEL = centos = AWS linux = fedora

yum --> dnf

/etc/yum.repos.d/

*.repo files --> yum install nginx