Cloud Design Requirements & Software Architectures (Lecture 3)

Question 1

What is requirements engineering?

Answer 1

-> process of eliciting, analysing, documenting, validating & managing the requirements of a software

Question 2

Typical requirements (or oppsite)

Answer 2

requirements:
- functionality
- user interaction
- error handling

no requirements:
- system design
- implemenation
- development method

–> WHAT, NOT HOW

Question 3

Stages of requirements engineering

Answer 3

1. Elicitation
   -> gathering requirements from endusers (workshops, interviews)
2. Analysis
   -> analyze & prioritize requirements
3. Specifiaction
   -> documentation of requirements
4. Verification & Validation
   -> ensuring that the requirements are complete and correct
5. Management
   -> tracking changes of requirements
6. Maintenance
   -> managing changer of requirements over time

Question 4

Types of requirements

Answer 4

function requirements:
- specific task and functions
- expressed in user cases

non- functional requirements:
- characterisitcs or qualities
–> performance, usability, reliability

Question 5

Non-functional requirements (7)

Answer 5

1. Performance
   –> Latency : time between request and response
   –> Throughput: number of people you can serve
   –> Utilization: percentage of used capacity
2. Scalability
   –> vertical scaling
   - parallelism with multicores

–> horizontal scaling
- adding more machines

–> A Elasticity
- ability to expand and shrink

3. Reliability
   - safe from bugs
4. Availability
   minimize downtime
   four 9: hour per year
   five 9: 5 minutes per year
5. Secrurity
   - protected from unauthorized access
   - what you store an what you get has to be the same (integrity)
6. Maintainability
   -> you have to be always able to make some changes
7. Deployability
   - can be taken from development to porduction

Question 6

What is software architecture

Answer 6

definiert die:
- Komponenten einer Software
- wie sie miteinander interagieren
- wie sie verpackt sind

Question 7

Klassische 3 Tier Architecture

Answer 7

Presentation -> UI
I
I
V
Application -> logic / Brain behind application
I
I
V
Data -> Stores the information

Question 8

Monolithic Architecture (+/-)

Answer 8

everything is packaged in a single programm
+:
Testing
Debugging
Monitoring
Deployment
-:
strong dependency
many testing
scaling

for scaling : load balancer: balances multiple clients on multiple Monolithic blocks

Question 9

Microservice Architecure (key principles, +/-)

Answer 9

• split the Monolithic block in small functionel units

key principles:
- loose coupling:
– changing one microservice does not require a change of everything

-high functional cohesion:
– everyone of them has a single, well defined purpose
– everyone has their own database!!

+:
Technical heterogenty
-> you can use the best Technology for each different parts

-:
complex
remote calls instead of function calls -> latency
Monitoring
- divers team of experts
- Data consistency (Cache Kohärenz)

Question 10

How to ensure Data consistency

Answer 10

Two phase commit:
every participant has to agree on the results, if one disagrees, its not commited
prepare phase <-> commit/rollback phase

Saga Pattern
every service runs a local Transaction & report success/failure