Aggregate Pipelines Mongodb

https://www.youtube.com/watch?v=Kk6Er0c7srU
Aggregate Pipelines Mongodb

db.purchase_orders.aggegate(
	[
		{$match : {customer : {$in : ["Mike", "Karen"]}}}
		{$group : {
			_id: "$product",
			total:{$sum : "$total"}
			}
		}
		{$sort  : {total : -1}}
	]
)

Fonts, Web Safe Fonts, Web Open Font Format

Web Safe Fonts 
Arial, Courier New, Times New Roman, and Verdana are common web safe fonts.
These are available on All Machines.

https://blogpros.com/blog/2018/10/add-custom-fonts-blog 
Throughout the years, there have been a few workarounds to get fonts to display. Some old websites would use scripts that tried to get the user to download a font to use to display the site correctly, but this is incredibly dangerous. 

Web Fonts - WOFF - Web Open Font Format
Then, in 2010, the Mozilla Foundation, Microsoft, and Opera banded together to get the W3C to support the WOFF format. WOFF, or Web Open Font Format, supports a number of fonts and works in that same old method, simply downloading and using the font in the background. However, because it’s a limited and verifiable format, it’s not exploitable by malware.

Whats Cloud Native

 “Cloud native computing uses an open source software stack to be:

1. Containerized. Each part (applications, processes, etc) is packaged in its own container. This facilitates reproducibility, transparency, and resource isolation.
2. Dynamically orchestrated. Containers are actively scheduled and managed to optimize resource utilization.
3. Microservices-oriented. Applications are segmented into microservices. This significantly increases the overall agility and maintainability of applications.”

“An approach that builds software applications as microservices and runs them on a containerized and dynamically orchestrated platform to utilize the advantages of the cloud computing model.”

POC - Microservices - Java Spring Cloud

Microservices POC 

https://www.youtube.com/watch?v=y8IQb4ofjDo&list=PLqq-6Pq4lTTZSKAFG6aCDVDP86Qx4lNas [JavaBrains]

https://www.youtube.com/watch?v=BnknNTN8icw [DailyCodeBuffer]

https://www.youtube.com/watch?v=tuJqH3AV0e8 [Edureka]

https://www.youtube.com/watch?v=tljuDMmfJz8&t=123s [Java Techie]

https://www.youtube.com/watch?v=rlS9eH5tEnY [Tech Primers]

https://www.youtube.com/watch?v=SzbeDqBSRkc  [PlayJava]

--------------------------------------------------------------------------------------------------------------------

Zuul POC 
https://www.youtube.com/watch?v=-I-9gK8NWXY
https://www.youtube.com/watch?v=6aG0xFpeNFw

Spring Cloud
https://spring.io/projects

Spring Cloud Gateway

https://www.youtube.com/watch?v=CJQiB9ObvaM

https://spring.io/projects/spring-cloud-gateway

To run your own gateway use the spring-cloud-starter-gateway dependency.

https://spring.io/projects/spring-cloud-circuitbreaker

Hystrix - org.springframework.cloud:spring-cloud-starter-netflix-hystrix

Circuit Breaker Pattern

https://techblog.constantcontact.com/software-development/circuit-breakers-and-microservices/

Spring Boot vs Spring Cloud

https://www.educba.com/spring-cloud-vs-spring-boot/

API Gateway, Zuul

https://www.youtube.com/watch?v=1vjOv_f9L8I

An API gateway is a vital component in any microservice architecture. - An Edge Service
1 Microservice acts as a Gateway for rest of microservices

API Gateway is an abstraction layer - a FACADE

If We have microservices URL and those URLs are directly used by Client UI Developers

it would create issues later if we would like to change them in future.

So, We can have a FACADE Layer which would abstract real URLS

This can be achieved by Using API Gateway - A kind of Edge Service

Netflix has an open source library for this purpose called "Zuul"

API Composition - Making 1 Microservice out of many other

Single Point of Entry

Monitoring System for Requests/Responses

External Contract  ----------> Zuul Gateway ------> Internal Rest API

 

Advantages

• Monitoring 
• Authentication

Disadvantages & Mitigation Steps

• Little bit Slow - 1 Additional Network Hop 
• Single Point of Failure - You need to have multiple redundant Zuul Gateway  to overcome it
• Backend for Frontend - Different Backend for Android, Apple, Web - Layers - Different API Gateway for Different Types of Frontend

Works on Filter Based Design Pattern
PreFilter
PostFilter
etc

Edge Services

 Any Service which is located close to user and which actually reduces latency by providing   CDN services, API Gateway, DDOS Prevention(Rate Limiting) - They are collectively called EDGE Services 

CDN  - Content Delivery Network

Throttle - DDOS Prevention

API Gateway 

Filtering 

Authentication

Logging

https://medium.com/knerd/api-infrastructure-at-knewton-whats-in-an-edge-service-51a3777aeb41 

Types of Deployment/Release

http://blog.itaysk.com/2017/11/20/deployment-strategies-defined 

• Reckless Deployment - 3 Old --> 3 New ---Full Downtime Required, Old ones are lost
• Rolling Upgrade - Minimal Downtime, Mutable Servers, Servers Refreshed 1 By 1
• Blue/Green Deployment - 3 Old, 3 New - Parallel - All Users are taken to New, Old is still kept as such  and in case need arises all users are sent to old one, Here we have exact replica of PROD with old and new both - immutable Instances. we configure reverse proxy to direct to New One and then if anything bad happens we can flip switch back to old one, Its bit riskier
• Canary Deployment - 3 Old, 1 New - Parallel - 95% Users see Old, 5% see new, So, Basically, Canary is toned-down/cautious risk-averse version of Blue-Green, Here we show new App to few users and verify APP performance and all , If all is good, we go ahead and show more users new APP and gradually all Users are ported to new APP
• Versioned Deployment - Users Choose which one to use, You have both versions 

https://martinfowler.com/bliki/CanaryRelease.html

Blue-green Deployments, A/B Testing, and Canary Releases – Software Blog (christianposta.com)

1 More type of Release is there - not a typical release though but somewhat similar - A/B Testing

https://en.wikipedia.org/wiki/A/B_testing

https://vwo.com/ab-testing

Mostly related to UI /Human Computer Interaction- Here we check which Color/Design User looks better, Which Site brings more users back to site again, Time They spend on each site.