Wk 7 Cloud Computing And Wk 8 Testing In Production

Question 1

Serverful model

Answer 1

• IaaS : infrastructure as a service
• Paas : platform as a service
• Saas : software as a service

Question 2

Iaas

Answer 2

Cloud provider gives access to bare servers

Question 3

Paas

Answer 3

Provider gives access to servers with operating systems and tools

Question 4

Saas

Answer 4

Provider gives access to applications on a subscription bases

Question 5

Severful implementation

Answer 5

Makes use of multi tenancy by virtualization using :
- Virtual machines
- Containers
- orchestration and version control

Question 6

Virtual machine multi tenancy :

Answer 6

A Number of virtual machines VM⁰…VMN may be run on a physical machine by a hypervisor

Fine for sharing performance but not good for sharing network

Question 7

What is a hypervisor?

Answer 7

Maps virtual resources to physical ones ensuring they are shared fairly

Question 8

Why would you want to move a virtual machine between physical ones ?

Answer 8

So you may shut a physical one down.

Question 9

Disadvantages of virtual machines

Answer 9

Virtual machines are heavy and inconvenient for small computations.

Question 10

Containers

Answer 10

Many containers may run on a physical machine. Each container does not have a kernel and rater it has the same operating system as the kernel of the physical machine.

The physical machine’s operating system maps the resources to the containers ensuring fairness.

Question 11

Pro and cons of containers

Answer 11

Pro faster than VMs
Con if the kernel crashes all the containers crash with it

Question 12

Serverful cost model

Answer 12

Charges resource allocation on a rental bases

Question 13

Serveful microservice potential implementations:

Answer 13

• one service per virtual machine
• one service per container

Question 14

Serverful : one service per virtual machine

Answer 14

• expensive as you would have many machines🫰🫰🫰
• issues with one machine would not affect other machines

Question 15

Serverful: one service per container

Answer 15

• fast
• cheaper
• if server crashes so do all other containers

Question 16

Serverless computing:

Answer 16

As a user you don’t have to worry about operational concerns.( Servers are still used )

Models :
- Baas
- Faas

Question 17

Baas : Backend as a service

Answer 17

Cloud provider gives access to a service such as authentication or database storage.

Question 18

Faas: Function as a service

Answer 18

Cloud provider rents custom code in response to requests and events

Question 19

Serveless costs

Answer 19

Per function application
For execution time
Pay as you go

Question 20

Microservices Serverless implementation:

Answer 20

• map a single function instance to a single microservice ( wasteful)
• map multiple functions per machine
  ( Maintenance and performance issues )

Question 21

API Gateway

Answer 21

Acts as a proxy trough which http requests and responses are used to make function calls.

Question 22

IaC : infrastructure as a code

Answer 22

Configures ( virtual) infrastructure using executable code, which can be stored in version control

( Scripts for virtual machines)

Question 23

Why test in production?

Answer 23

• Volume
• Real users (powerful feedback)

Question 24

Types of testing

Answer 24

• Blue Green testing
• Canary testing
• A/B feature testing
• resiliance testing

Question 25

Blue green

Answer 25

Staging ( 🍏 ) gets uploaded to production ( 🔵) .
If an issue arrises the changes are switched back to staging. This happens through a routing table.

Question 26

Canary testing

Answer 26

A small percentage of customer traffic is sent to a new version of the system ( tinker with load balance)
( error testing)

Question 27

A/B feature testing

Answer 27

A small percentage of the customer traffic is sent to a new version of the production environment. (Used for UI testing )

Question 28

Resiliance testing

Answer 28

Random VM or containers are terminated in the production environment.

Question 29

Netflix test strategies

Answer 29

• caos monkey
• caos gorilla
• latency monkey

Question 30

Caos monkey 🐒

Answer 30

Terminates random VMs. This ensures that the recovery plan is constantly tested.

Question 31

Caos gorilla 🦍

Answer 31

Terminates network connections between zones ( geographical potentially such as Devon region is disconnected traffic should be redirected)

Question 32

Latency monkey 🐵

Answer 32

Delays client server communication, measures upstream and downstream services and checks that they respond appropriately

Question 33

Staging environment

Answer 33

Scale down replica of the production environment

Question 34

Cloud computing

Answer 34

Many enterprises don’t own the infrastructure that provides the staging environment but rent it in the “cloud ☁️”

Question 35

Cloud architecture provides

Answer 35

• broad network access
• on demand self service
• measured services
• rapid elasticity
• resource pooling
• assurance

Question 36

broad network access

Answer 36

Cloud is available over standard networks

Question 37

on demand self service

Answer 37

Often you get free trials. Very easy entry requirements.

Question 38

measured services

Answer 38

The provider monitors and charges for what is used

Question 39

rapid elasticity

Answer 39

Easily acquire or release machines

Question 40

resource pooling

Answer 40

Achieve multi tenancy on one physical machine to multiple virtual ones

Question 41

Assurance

Answer 41

Cloud services are staffed by the top people in the field.

Can afford the best and most up to date equipment.

Hardened by continuous hacking.

Question 42

Cloud computing reasons to adopt it :

Answer 42

• shift from expenditures on datacenters to steady operational spendure
• avoid being locked by one company who can charge what they like
• increase security
• availability multiple datacenters
• performance

Question 43

A/b vs Blue Green

Answer 43

Ab : compare between two versions , user experience comparison
Blue green switching of production with staging.