Developing on AWS Note.1 - AWS Models, EC2, ELB, autoScaling

Cloud AWS EC2 ELB AutoScaling

创建时间:2020-01-29 14:58

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0. Overview
1. Cloud computing definition
2. Models of Cloud Computing
3. AWS Service Stack
4. Compute services
5. Exceptions and Errors handle

0. Overview

We use SDKs to interract with Application Programing Interface(API), and then connect to all AWS services.

1. Cloud computing definition

enable you to stop thinking of your infrastructure as hardware, and instead think of it and use it as software.

2. Models of Cloud Computing

IaaS (Infrastructure as a Service)
- basic buiding blocks for Cloud IT
  - Networking features
  - Computers
  - Data storage space
- PaaS (Platform as a Service)
  - enables you to run applications without the need to manage underlying infrastructure(hardware and operating systems)
- SaaS (Software as a Service)
  - A complete product that is run and managed by the service provider
    3. AWS Service Stack
Infrastructure
- Regions
- Availability Zones
- Edge Locations
Foundation Services
- Compute
  - virtual instances
  - auto scaling
  - load balancing
- networking
- storage
  - object
  - block
  - archive
Platform Services
- Compute
  - AWS Lambda
  - AWS Elastic Beanstalk
  - Amazon ECS
  - Amazon EKS
- database
  - relational
  - No SQL
  - Caching
  - Products
    - DynamoDB
    - RDS - relational database service
    - Elastic Cache
    - Redshift - data warehouse, for analysis and migration
- Analytics
  - Cluster computing
  - real time
  - data warehouse
  - data workflows
  - Products
    - EMR - managed hadoop framework
    - Kinesis
    - CloudSearch
    - ElasticSearch
- App services
  - Queuing
  - Orchestration
  - App streaming
  - Transcoding
  - Email
  - Search
  - Products
    - SQS
    - SNS
    - SES
    - Amazon Step Functions
- Deployment and management
  - containers
  - Dev/ ops tools
  - resource templates
  - usage tracking
  - monitoring and logs
  - products
    - CodeCommit
    - CodeDeploy
    - CodePipeline
    - CodeBuild
    - X-Ray
- Mobile Services
  - identity
  - sync
  - mobile analytics
  - notifications
  - products
    - Cognito
    - Pinpoint
    - API gateway
Applications
- Virtual Desktops
- Collaboration and Sharing

4. Compute services

4.1 EC2

Computers in the cloud.
Can create images of your servers at any time with a few clicks or simple API call.
different instance type for different use cases:
- low traffic websites
- small database
- high performance web services
- high performance databases
- distributed memory caches
- data warehousing
- log or data-processing applications
- 3D visualizations
- Machine learning
Pricing
- on demand
- reserved instances
- spot instances

4.2 ELB - Elastic Load Balancing

distribute traffic across multiple EC2 instances, in multiple Availability Zones
Support health checks to detect unhealthy Amazon EC2 instances
- To discover the availability of instances, a ELB periodically sends pings, attempts connections or sends requests to test the EC2 instances.
Supports the routing and load balancing of traffic to Amazon EC2 instances.
when the LB determins that an instance is unhealthy, it stops routing requests to that instance.
sticky sessions
- enables the load balancer to bind a user’s session to a specific server instance.
we should get rid of sticky sessions since:
- limit application’s scalability
- lead to unequal load across servers
- affect end-user response time since a single user’s load isn’t even spread across servers.
Instead of using sticky sessions: cache
- manage user sessions by
  - store locally to the node responding to the HTTP request
  - designate a layer which can store those sessions in a scalable and robust manner.
- Duration based session stickiness
  - LB uses a special LB generated cookie to rack the application instance for each request. When the load balancer reveives a request, it first checks to see whether this cookie is present in the request. If so, the reqeust is sent to the application instance specified in the cookie. If not, the LB chooses an application instance based on the existing load balancing algo. A cookie is inserted into the response for binding subsequent requests from the same user to that application instance. The stickiness policy configuration defines a cookie expiration, which establishes the duration of validity for each cookie. Cookie will be automatically updated after its duration expires.
- Application base session stickiness
  - LB uses a special cookie to associate the session with the original server that handled the reqeust. But follows the lifetime of the application-generated cookie corresponding to the cookie name specified in the policy configuration.
  - The LB only inserts a new stickiness cookie if the application response includes a new application cookie.
  - The load balancer stickiness cookie does not update with each request. If the application cookie is explicitly removed or expires, the session stops being sticky until a new application cookie is issued.
  - Application often store session data in memory, but this approach does not scale well
Methods available to manage session data without sticky sessions include:
- using ElasticCache to store session data
- using Amazon DynamoDB to store session data

4.3 Auto Scaling

Auto Scaling helps you ensure that you have the correct number of EC2 instances available to handle the load for your application. Auto Scaling is particularly well-suited for applications that experience hourly, daily, or weekly variability in usage.

5. Exceptions and Errors handle

400 series: handle error in application
500 series: retry operations

Java SDK throes the following unchecked(runtime) exceptions when error occur:

AmazonServiceException
- indicates that the reqeust was correctly transmitted to the service, but for some reason, the service was not able to process it, and returned an error response instead.
AmazonClientException
- indicates that a problem occured inside the hava client code
  - try to send a request to AWS
  - try to parse a response from AWS
IllegalArgumentException
- throw if you pass an illegal argument when performing an operation on a service

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