Developer Theory

Question 1

What does CI/CD stand for and what does the different parts mean? Which AWS service is connected to what part?

Answer 1

1. Continuous Integration
   - Integrating or merging the code changes frequently (at least once per day).
   - Think CodeCommit
2. Continuous Delivery
   - Automating the build, test and deployment functions
   - Think CodeBuild and CodeDeploy
3. Continuous Deployment
   - Fully automated release process. Code is deployed into Staging or Production as soon as it has successfully passed through the release pipeline.
   - Think CodePipeline

Question 2

Describe CodeCommit’s three main characteristics.

Answer 2

1. Centralize Code Repository
   - A place to store source code, binaries, libraries, images, HTML files, etc.
   - Base on Git
2. Enables Collaboration
   - Manages updates from multiple users
3. Version Control
   - Tracks and manages code changes.
   - Maintains version history

Question 3

What are the two ways to perform a code deploy using CodeDeploy?

Answer 3

• In-Place/Rolling update
• The application is stopped on each instance and the new release is installed (one at the time)
• Capacity is reduced during the deployment
• Lambda is not supported
• Rolling back involves a re-deploy
• Great when deploying for the first time or for Test/Dev
• Blue/Green
• New instances are provisioned and the new release is installed on the new instances
• Blue refers to the old environment, green to the new
• No capacity reduction
• Green instances can be created ahead of time
• Easy to switch between old and new, if you change you mind you can simply set the Load Balancer to direct the traffic back to the old environment
• You pay for 2 environments until you terminate the old servers

Question 4

What is the config file for CodeDeploy called?

Answer 4

• Appspec file (appspec.yml or appspec.json)
• Main configuration file for CodeDeploy.
• Defines the parameters to be used by CodeDeploy, e.g. OS, files, hooks

Question 5

Where is CodeDeploy’s appspec.yml located?

Answer 5

The root folder of your revision

Question 6

In CodeDeploy, what are “hooks”?

Answer 6

• Lifecycle events hooks that have a specific run order.

- Relates to different scripts you need to run during different stages of the deployment

Question 7

In CodeDeploy’s appspec.yml, what are the three main parts and what do they do?

Answer 7

• OS
• What OS to run
• Files
• Source and destination for any files that should be copied across during the deployment
• Hooks
• Lifecycle events hooks that are run in a specific order known as Run Order
• Specifies all the scripts we want to run during the deployment, and in which stage of the deployment the should be run

Question 8

What are the three main phases of a In-Place Deployment using CodeDeploy (EC2)?

Answer 8

• De-registering with the Load Balancer
• Installation
• Re-registering with a Load Balancer

Question 9

In a In-Place Deployment using CodeDeployment, what three phases comes before installation (EC2)?

Answer 9

• BeforeBlockTraffic
• Tasks you want to run on the instance before they are de-registered from a Load Balancer
• BlockTraffic
• De-register instances from a Load Balancer
• AfterBlockTraffic
• Tasks you want to run on instances after they are de-registered from a Load Balancer

Question 10

In a In-Place Deployment using CodeDeployment, what 7 phases comes during the installation step (EC2)?

Answer 10

• ApplicationStop
• Gracefully stop the application
• DownloadBundle
• CodeDeploy agent copies tha application reversion files to a temporary location
• BeforeInstall
• Pre-install scripts, e.g. backing up the current version, decrypting files
• Install
• Copy application reversion files to final location
• AfterInstall
• Post-install scripts, e.g. configuration, file permissions
• ApplicationStart
• Start any services that were stopped during ApplicationStop
• ValidatService
• Run tests to validate the service

Question 11

In a In-Place Deployment using CodeDeployment, what three phases comes after installation (EC2)?

Answer 11

• BeforeAllowTraffic
• Tasks you want to run on the instances before they are registered with the Load Balancer
• AllowTraffic
• Register instances with a Load Balancer
• AfterAllowTraffic
• Tasks you want to run on the instances after they are registered with a Load Balancer

Question 12

What three characteristics describes CodePipeline?

Answer 12

1. Continuous Integration/Continuous Delivery service
   - Orchestrates your end-to-end software release process based on a workflow you define
2. Automated
   - Automatically triggers your pipeline as soon as a change is detected in your source code repository
3. Integrates with AWS and Third-Party tools
   - CodeCommit, CodeBuild, CodeDepoly
   - Lambda, CloudFormation, Elastic Beanstalk, Elastic Container Service
   - Jenkins, GitHub

Question 13

What is a container?

Answer 13

A virtual operating environment with everything the software needs to run.

• Includes libraries, system tools, code, and runtime.
• Allows applications to be built using independent stateless components or microservices running in multiple containers.

Question 14

What is Elastic Container Service? Elastic Container Registry?

Answer 14

• Elastic Container Service:
• Container orchestration service.
• ECS will run your containers on clusters of virtual machines.
• Deploys containers from the images stored in ECR
• Elastic Container Registry:
• Registry for your container images

Question 15

Name three Docker commands.

Answer 15

1. docker build
   - docker build -t myimagerepo
   - builds the image
2. docker tag
   - docker tag myimagerepo:latest .dkr.ecr.eu-west-1.amazonaws.com/myimagerepo:latest
   - add a tag/alias to an image (above we added ‘latest’)
3. docker push
   - docker push .dkr.ecr.eu-west-1.amazonaws.com/myimagerepo:latest
   - pushes the image to the Elastic Container Service Repository where it can be accessed by Elastic Container Service

Question 16

In CodeBuild, what is the file that defines build commands and settings used to run your build called?

Answer 16

buildspec.yml

Question 17

In CodeBuild, how can you override the settings in buildspec.yml?

Answer 17

By adding your own commands in the console when launching the build. (by default CodeBuild is looking for a file called buildspec.yml)

Question 18

If something goes wrong with a build, where can you find information about it?

Answer 18

Build logs appear in the CodeBuild console and you can also view the CodeBuild log in CloudWatch.

Question 19

What is CloudFormation?

Answer 19

CloudFormation is used to manage, configure and provision AWS infrastructure as code.

Question 20

What are the main sections of a CloudFormation templates file? What is it written in?

Answer 20

• Written in YAML or JSON
• Parameters
• Input custom values
• Conditions
• Provision resources based on conditions, for example based on the environment
• Resources
• The AWS resources to create
• Only mandatory section
• Mappings
• Custom mappings
• E.g. the AMI you want to use for a specific region
• Transforms
• Reference code located in S3, e.g. Lambda code, reusable snippets of code
• Specify the use of SAM

Question 21

What is SAM?

Answer 21

• Serverless Application Model

- Used to define and provision serverless applications using CloudFormation

Question 22

Name two SAM CLI command.

Answer 22

• sam package
• packages your application and uploads to S3
• sam deploy
• deploys your serverless application using CloudFormation

Question 23

In CloudFormation, what is Nested Stacks?

Answer 23

• Allows you to re-use your CloudFormation code so we don’t need to do a copy/paste
• Used for frequently used configurations like for Load Balancers, web servers and application servers
• You create a CloudFormation template, store it in S3 and reference it in the Resources section as “stack”.

Question 24

When using CodeCommit, how is the data/code protected in transit?

Answer 24

HTTPS or SSH

Question 25

In CodeCommit, how can I set up to be notified if there is a change in the code?

Answer 25

You can configure notifications using SNS and CloudWatch to send notifications to subscribers when certain events happens in your CodeCommit repository. - e.g. when somebody does a pull request, closes a pull request, or comments on a pull request - in CodeCommit you set up a CloudWatch event rule and an SNS topic for people to subscribe to * Note: I think the above is what they say in the video, but in AWS documentation it seems like CloudWatch has nothing to do with the Notifications, only SNS. - I think that it might be possible (if I understand the documentation correctly) that you can use EventBridge (CloudWatch Events-ish?) to to route data to SNS, and thereby using both EventBridge and SNS to get notifications when there are changes in CodeCommit. But, it does seem to be some extra work comparing to simply specifying an SNS topic under "Notifications" in CodeCommit (even though this easier option seems to be more limited).

Question 26

Does CodeDeploy work with EC2, Lambda and On-premises?

Answer 26

Yes.

Question 27

What is the Appspec for CodeDeploy written in?

Answer 27

- YAML if it is for EC2 or on-premises systems - YAML or JSON is you are working with Lambda - The file structure depends on whether you are deploying to Lambda or EC2

Question 28

CodeDeploy: name three types of scripts that you might want to run during a deployment.

Answer 28

1. Unzip files - Unzip files prior to deployment 2. Run tests - Run functional tests on a newly deployed application 3. Deal with Load Balancing - De-register and re-register instances with a Load Balancer

Question 29

How does CodeDeploy know what EC2 instance it should deploy the application to?

Answer 29

The EC2 instance must have a tag, and when you create a deployment group in CodeDeploy (that your application should be deployed to) you simply specify the tag of the EC2 instance you want to deploy to.

Question 30

What are the two options to run containers in Elastic Container Service?

Answer 30

1. Clusters of Virtual Machines - ECS will run your containers on clusters of EC2 instances. - Use if you want to control the installation, configuration and management of your compute environment 2. Fargate for Serverless - Use Fargate for Serverless containers and you don't need to worry about the underlying EC2 instances.

Question 31

What is the CloudFormation template written in?

Answer 31

YAML or JSON

Question 32

What does it cost to use CloudFormation?

Answer 32

Nothing, you only pay for the resources you create.

Question 33

You upload the CloudFormation template to CloudFormation, but where is it stored?

Answer 33

S3

Question 34

What is a CloudFormation stack?

Answer 34

All the resources that will be (/has been?) deployed by CloudFormation (from the template)

Question 35

If something fails during the creation of a CloudFormation stack, is it rolled back by default?

Answer 35

Yes, the entire stack is per default rolled back. This can be changed. Disabling rollback can be useful for example is you want to debug a stack that is a constantly failing.

Question 36

Which element is the only mandatory in a CloudFormation Nested Stack?

Answer 36

TemplateURL. This has to point to a template in a S3 bucket

Question 37

In what part of of a CloudFormation template can you reference a Nested Stack?

Answer 37

In the Resource section, using the type "Stack" ("AWS::CloudFormation::Stack").

Question 38

You are using CodePipeline to automatically deploy your code every time there is a commit to CodeCommit. If one of your automated tests fails, what happens?

Answer 38

The pipeline stops immediately because one stage has failed.