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AWS Solution Architect Associate - SAA-CO3 > Section 4: Elastic Load Balancing and Auto Scaling > Flashcards

Section 4: Elastic Load Balancing and Auto Scaling Flashcards

1
Q

Scaling Up (vertical scaling)

A
  • Adding resources to the instance.
  • Limitation is still have a single point of failure (SPOF).
  • Can reach limit.

Example: t2.micro, 1vCPU, 1 GB RAM to c5.xlarge, 4vCPU, 8GB RAM.

Lesson 56

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2
Q

Scaling Out (horizontal scaling)

A
  • Add one or more instances.
  • Resiliency.
  • Unlimited.

Example: add more t2.micro to existing t2.micro.

Lesson 56

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3
Q

Amazon EC2 Autoscaling (Dynamo and ECS also supported)

A
  • EC2 Auto Scaling launches and terminates instances dynamically.
  • Scaling is horizontal (scales out).
  • Provides elasticity and scalability.
  • Cannot scale across Regions.
  • Responds to EC2 Status Checks and CloudWatch metrics.
  • Can scale based on demand (performance) or on a schedule.
  • Scaling policies define how to respond to changes in demand.
  • Auto Scaling groups define collections of EC2 instances that are scaled and managed together.

Lesson 57

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4
Q

Configuration Steps of an Auto Scaling Group

A
  1. A Launch Template specifies the EC2 instance configuration.
    1b. A Launch Configuration replaced by a Launch Template) has fewer features.
  2. Configure purchase option - On-Demand vs Spot.
  3. Configure VPC and Subnets.
  4. Attach Load Balancer.
  5. Configure health checks EC2 and ELB.
  6. Group size and scaling policies.

Lesson 57

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5
Q

Launch Template information

A
  • AMI and instance type.
  • EBS volumes.
  • Security Groups.
  • Key Pair.
  • IAM Instance profile.
  • User data.
  • Shutdown behavior.
  • Termination protection.
  • Placement Group Name.
  • Capacity Reservation.
  • Tenancy.
  • Purchasing Option (e.g. Spot).

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6
Q

Launch Configuration information

A
  • AMI and instance type.
  • EBS volumes.
  • Security Groups.
  • Key Pair.
  • Purchasing Option (e.g. Spot).
  • IAM instance profile.
  • User data.

Lesson 57

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7
Q

Amazon EC2 Auto-Scaling Health Checks

A

EC2 = EC2 status checks.
ELB = (Recommend enabling) Uses the ELB health checks in addition to EC2 health checks.

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8
Q

Amazon EC2 Auto Scaling Health Check Grace Period

A
  • How long time wait before checking the health status of the instance.
  • Auto Scaling does not act on health checks until grace period expires.

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9
Q

Amazon EC2 Auto Scaling Monitoring

A

Group Metrics (ASG):
- Data points about the Auto Scaling Group.
- 1-minute granularity.
- No charge.
- Must be enabled.

Basic Monitoring (Instances):
- 5-minute granularity.
- No charge.

Detailed Monitoring (Instances):
- 1-minute granularity.
- Charges apply.
- Enabled by default when creating launch configurations through the CLI.

Lesson 57

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10
Q

Additional Scaling Settings

A
  • Cooldowns - Used with simple scaling policy to prevent Auto Scaling from launching or terminating before the effects of previous activities are visible. Default value is 300 seconds (5 minutes).
  • Termination Policy - Controls which instances to terminate first when a scale-in event occurs.
  • Termination Protection - Prevents Auto Scaling from terminating protected instances.
  • Standby State - Used to put an instance in the InService state into the StandBy state, update or troubleshoot the instance.
  • Lifecycle Hooks - Used to perform custom actions by pausing instances as the ASG launches or terminates them.
    Use case:
  • Run a script to download and install software after launching.
  • Pause an instance to process data before a scale-in (termination) (e.g. extract a log file).

Lifecycle diagram in PPT.

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11
Q

Load Balancing and High Availability

A
  • Distribute the connections to multiple instances (and can be in multiple AZs).
  • If an instance fails, the load balancer will re-route the connection.
  • Regularly use Auto Scaling and Load Balancing together.

Lesson 59

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12
Q

(ELB) Application Load Balancer (ALB) - Layer 7 (HTTP, HTTPS)

A
  • Operates at the request level.
  • Routes based on the content of the request (layer 7).
  • Supports path-based (URL) routing, host-based (Domain name) routing, query string parameter-based (URL) routing, and source IP address-based routing.
  • Supports instances, IP addresses, Lambda functions and containers as targets.

Load balancer protocol - HTTP, HTTPS.

Lesson 60

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13
Q

(ELB) Network Load Balancer (NLB) - Layer 4 (TCP, TLS, UDP, TCP_UDP)

A
  • Operates at the connection level.
  • Routes connections based on IP protocol data (layer 4).
  • Offers ultra-high performance, low latency, and TLS offloading at scale.
  • Can have a static IP / Elastic IP.
  • Supports UDP and static IP addresses as targets.

Lesson 60

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14
Q

(ELB) Classic Load Balancer (CLB) (deprecated) - Layer 4 and 7

A
  • Old generation, not recommended for new applications.
  • Performs routing at Layer 4 and Layer 7.
  • Use for existing applications running in EC2-Classic.

Lesson 60

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15
Q

(ELB) Gateway Load Balancer (GLB) - Layer 3

A
  • Used in front of virtual appliances such as firewalls, IDS/IPS, and deep packet inspection systems.
  • Operates at Layer 3 - listens for all packets on all ports.
  • Forwards traffic to the Target Group (TG) specified in the listener rules.
  • Exchanges traffic with appliances using the GENEVE protocol on port 6081.

Lesson 60

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16
Q

Application Load Balancer (ALB) Featues

A
  • OSI Layer - 7.
  • Target Type - IP, instance, Lambda, ECS.
  • Protocol Listeners - HTTP, HTTPS, gRPC.
  • *PrivateLink support** - No.
  • Static IP address - No.
  • HTTP header based routing - Yes.
  • Source IP preservation - x-forwarded-for.
  • SSL termination - Load Balancer.

Lesson 60

17
Q

Network Load Balancer (NLB) Features

A
  • OSI Layer - 4
  • Target Type - IP, instance.
  • Protocol Listeners - TCP, UDP, TLS.
  • *PrivateLink support** - (TCP, TLS).
  • Static IP address - Yes (good for Whitelisting and Firewalls).
  • HTTP header based routing - No.
  • Source IP preservation - Native.
  • SSL termination - Load Balancer or target.

Lesson 60

18
Q

Application Load Balancer (ALB) Use Cases

A
  • Web applications with L7 routing (HTTP/HTTPS).
  • Microservices architectures (e.g. Docker containers).
  • Lambda targets.

Lesson 60

19
Q

Network Load Balancer (NLB) Use Cases

A
  • TCP and UDP based applications.
  • Ultra-low latency.
  • Static IP addresses.
  • VPC endpoints.

Lesson 60

20
Q

Gateway Load Balancer (GLB) Use Cases

A
  • Load balance virtual appliances such as:
    • Intrusion Detection System (IDS).
    • Intrusion Protection System (IPS).
    • Next generation firewalls (NGFW).
    • Web application firewalls (WAF).
    • Distributed denial of protection systems (DDoS).
  • Integrate with Auto Scaling groups for elasticity.
  • Apply network monitoring and logging for analytics.

Lesson 60

21
Q

Cross-Zone Load Balancing

A

When cross-zone load balancing is enabled:
- Each load balancer node distributes traffic across the registered targets in all enabled AZs.

When cross-zone load balancing is disabled:
- Each load balancer node distributes traffic only across the registered targets in its AZ.

With Application Load Balancers, cross-zone load balancing is always enabled.

With Network Load Balancers and Gateway Load Balancers, cross-zone load balancing is disabled by default.

Lesson 68

22
Q

Session State

A

Use case: session data such as authentication details stored in a DynamoDB table.

ElastiCache is also a popular solution for storing session-state data.

Lesson 69

AWS Solution Architect Associate - SAA-CO3 (8 decks)

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