notes/session-12.txt at main · daws-88s/notes · GitHub

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Java
=====
Build tool -> Ant, Maven, Gradle, etc.
.java

JDK -> Java development kit
JRE -> Java Runtime environment

while developing we need JDK
while running JRE is enough

JDK = JRE + development utilities

Source code -> Compile -> Byte code -> 0 and 1
node js = compile + running
java = running directly

Build tool = Maven
output format -> .ear, .war, .jar
.jar has inbuilt lightweight server

Old Enterprise applications -> IBM Websphere, Oracle weblogic, JBOSS EAP, etc..
===========================
enterprise archive = frontend+backend+libraries -> .ear
roboshop.ear

1. tight couple
2. small problem makes both frontend and backend down
3. a small change is also costly. end to end testing should be done again
4. everytime frontend components should be downloaded from server

Jquery, Angular JS, etc..

Monolithic -> Apache Tomcat, JBOSS AS, etc.
=============
.war
frontend and backend
1. easy maintance
2. data only will be served by backend through API
3. loose coupling

problems
=========
1. problem in catalogue makes entire backend down
2. entire application should be developed in same programming language
3. tight coupling between backend components

Microservices -> inbuilt servers
=============
catalogue, user, cart, etc..

1. each component is independent
2. diff programming languages can be used
3. problem in one component cant disturb other components

nodejs =  node + npm
maven = java + maven

programming language == programming runtime
mvn clean package -> clean previous builds + install dependencies + pack the application

a new directory target will be created

Python
============
.py
pip
requirements.txt

1. OOPS
2. Scripting

frontend logs -> backend component logs -> DB is running fine or not

1. frontend nginx config recheck
2. backend may not be running
3. data is not loaded into DB
4. database is not running
5. DNS records are not updated

502 -> Bad gateway -> proxy server not able to get response from upstream server
500 -> internal server error -> proxy able to reach upstream server, but proper response is not there

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https://www.linkedin.com/posts/sivakumar-reddy-mettukuru_devops-cloudcomputing-sre-activity-7420307090109259776-ylTD?utm_source=share&utm_medium=member_desktop&rcm=ACoAABDIcU0BU8bgQnwg0jN1W2BYG8lApo6P9Ec