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AWScloud~5 mins

Spot Instances for cost savings in AWS - Commands & Configuration

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Introduction
Spot Instances let you use spare cloud computing power at a lower price. They help save money but can be stopped by the cloud provider when needed.
When running batch jobs that can pause and resume without issues.
When testing applications that do not need constant uptime.
When you want to save money on flexible workloads like data analysis.
When running background tasks that can handle interruptions.
When you want to reduce cloud costs for development environments.
Config File - spot-instance-launch-template.json
spot-instance-launch-template.json
{
  "LaunchTemplateName": "my-spot-launch-template",
  "LaunchTemplateData": {
    "InstanceType": "t3.medium",
    "ImageId": "ami-0abcdef1234567890",
    "InstanceMarketOptions": {
      "MarketType": "spot",
      "SpotOptions": {
        "MaxPrice": "0.03",
        "SpotInstanceType": "one-time",
        "InstanceInterruptionBehavior": "terminate"
      }
    },
    "KeyName": "my-key-pair",
    "SecurityGroupIds": ["sg-0123456789abcdef0"]
  }
}

This JSON file defines a launch template for an AWS EC2 Spot Instance.

  • InstanceType: The size of the virtual machine.
  • ImageId: The ID of the operating system image.
  • InstanceMarketOptions: Configures the instance as a Spot Instance with a maximum price and interruption behavior.
  • KeyName: The SSH key to access the instance.
  • SecurityGroupIds: The firewall rules applied to the instance.
Commands
This command creates a launch template for Spot Instances using the JSON configuration file.
Terminal
aws ec2 create-launch-template --cli-input-json file://spot-instance-launch-template.json
Expected OutputExpected
{ "LaunchTemplate": { "LaunchTemplateId": "lt-0abcd1234efgh5678", "LaunchTemplateName": "my-spot-launch-template", "CreateTime": "2024-06-01T12:00:00.000Z", "CreatedBy": "arn:aws:iam::123456789012:user/my-user", "DefaultVersionNumber": 1 } }
→
--cli-input-json - Specifies the JSON file with launch template details
This command starts one Spot Instance using the launch template created earlier.
Terminal
aws ec2 run-instances --launch-template LaunchTemplateName=my-spot-launch-template --count 1
Expected OutputExpected
{ "Instances": [ { "InstanceId": "i-0123456789abcdef0", "InstanceType": "t3.medium", "State": { "Code": 0, "Name": "pending" }, "LaunchTime": "2024-06-01T12:05:00.000Z" } ] }
→
--launch-template - Specifies the launch template to use
→
--count - Number of instances to launch
This command checks the status and details of the Spot Instance to confirm it is running.
Terminal
aws ec2 describe-instances --instance-ids i-0123456789abcdef0
Expected OutputExpected
{ "Reservations": [ { "Instances": [ { "InstanceId": "i-0123456789abcdef0", "InstanceType": "t3.medium", "State": { "Code": 16, "Name": "running" }, "LaunchTime": "2024-06-01T12:05:00.000Z" } ] } ] }
→
--instance-ids - Specifies which instance to describe
Key Concept

If you remember nothing else from this pattern, remember: Spot Instances save money by using spare cloud capacity but can stop anytime, so use them only for flexible tasks.

Common Mistakes
Trying to use Spot Instances for critical applications that must always run.
Spot Instances can be stopped by AWS at any time, causing downtime.
Use Spot Instances only for tasks that can handle interruptions or use On-Demand Instances for critical workloads.
Not setting a maximum price for Spot Instances.
Without a max price, you might pay more than expected or fail to get instances if the price rises.
Always set a reasonable max price in the launch template to control costs.
Not monitoring Spot Instance interruptions.
You might lose data or progress if the instance is terminated without preparation.
Use AWS tools or scripts to detect interruption notices and save work before termination.
Summary
Create a launch template specifying Spot Instance options and max price.
Launch Spot Instances using the created launch template.
Check instance status to confirm it is running and ready.
Remember Spot Instances can stop anytime, so use them for flexible workloads.

Practice

(1/5)
1. What is the main benefit of using Spot Instances in AWS?
easy
A. They offer unlimited storage space for your data.
B. They guarantee 24/7 uptime without interruptions.
C. They automatically scale your application based on traffic.
D. They provide significant cost savings by using spare capacity.

Solution

  1. Step 1: Understand Spot Instances purpose

    Spot Instances use spare AWS capacity and are cheaper but can be interrupted.

  2. Step 2: Compare options

    Only They provide significant cost savings by using spare capacity. mentions cost savings from spare capacity, others describe unrelated features.

  3. Final Answer:

    They provide significant cost savings by using spare capacity. -> Option D

  4. Quick Check:

    Spot Instances = Cost savings [OK]
Hint: Spot Instances save money by using spare capacity [OK]
Common Mistakes:
  • Thinking Spot Instances guarantee uptime
  • Confusing Spot Instances with auto-scaling
  • Assuming Spot Instances provide extra storage
2. Which of the following is the correct way to request a Spot Instance using AWS CLI?
easy
A. aws ec2 request-spot-instances --spot-price 0.05 --instance-count 1 --type t3.micro
B. aws ec2 create-spot-instance --price 0.05 --count 1 --instance-type t3.micro
C. aws ec2 spot-instance-request --max-price 0.05 --count 1 --instance t3.micro
D. aws ec2 launch-spot-instance --price 0.05 --number 1 --type t3.micro

Solution

  1. Step 1: Identify correct AWS CLI command

    The correct command is aws ec2 request-spot-instances with parameters like --spot-price, --instance-count, and --type.

  2. Step 2: Check options for syntax correctness

    Only aws ec2 request-spot-instances --spot-price 0.05 --instance-count 1 --type t3.micro uses the correct command and parameter names as per AWS CLI documentation.

  3. Final Answer:

    aws ec2 request-spot-instances --spot-price 0.05 --instance-count 1 --type t3.micro -> Option A

  4. Quick Check:

    Correct CLI syntax = aws ec2 request-spot-instances --spot-price 0.05 --instance-count 1 --type t3.micro [OK]
Hint: Use 'aws ec2 request-spot-instances' with correct flags [OK]
Common Mistakes:
  • Using wrong command names like create-spot-instance
  • Incorrect parameter names like --price instead of --spot-price
  • Mixing instance count and type flags
3. Consider this AWS CLI command output snippet after requesting Spot Instances: 
{
  "SpotInstanceRequests": [
    {
      "SpotInstanceRequestId": "sir-12345",
      "State": "active",
      "Status": {"Code": "fulfilled", "Message": "Your Spot request is fulfilled."},
      "InstanceId": "i-67890"
    }
  ]
}
What does this output indicate?
medium
A. The Spot Instance request is active and the instance is running.
B. The Spot Instance request was denied due to price limits.
C. The Spot Instance request is pending and waiting for capacity.
D. The Spot Instance request was cancelled by the user.

Solution

  1. Step 1: Analyze the 'State' and 'Status' fields

    The state is "active" and status code is "fulfilled", meaning the request succeeded and instance launched.

  2. Step 2: Interpret the meaning of 'InstanceId'

    The presence of an InstanceId means the Spot Instance is running.

  3. Final Answer:

    The Spot Instance request is active and the instance is running. -> Option A

  4. Quick Check:

    State active + fulfilled = running instance [OK]
Hint: Active state and fulfilled status mean instance is running [OK]
Common Mistakes:
  • Confusing 'active' with 'pending'
  • Ignoring the 'fulfilled' status message
  • Assuming InstanceId is missing means failure
4. You wrote this JSON snippet to request a Spot Instance but it fails: 
{
  "InstanceCount": 1,
  "Type": "one-time",
  "LaunchSpecification": {
    "InstanceType": "t3.micro",
    "ImageId": "ami-0abcdef1234567890"
  }
}
What is the likely error causing the failure?
medium
A. Wrong Type value; should be "persistent" only.
B. Missing the SpotPrice field to set max price.
C. Incorrect InstanceCount value; must be zero.
D. Invalid ImageId format; must be numeric only.

Solution

  1. Step 1: Check required fields for Spot Instance request

    Spot requests require a SpotPrice to specify max price willing to pay.

  2. Step 2: Validate other fields

    InstanceCount of 1 is valid, Type can be "one-time", and ImageId format is correct.

  3. Final Answer:

    Missing the SpotPrice field to set max price. -> Option B

  4. Quick Check:

    SpotPrice required for request [OK]
Hint: SpotPrice is mandatory in Spot Instance requests [OK]
Common Mistakes:
  • Omitting SpotPrice field
  • Using invalid Type values
  • Misunderstanding ImageId format
5. You want to run a batch job on AWS using Spot Instances to save costs. The job can be interrupted and resumed later. Which strategy best balances cost savings and job completion?
hard
A. Use Reserved Instances for guaranteed availability.
B. Request On-Demand Instances only to avoid interruptions.
C. Request Spot Instances with a low max price and use checkpointing to save progress.
D. Request Spot Instances with the highest max price to avoid interruptions.

Solution

  1. Step 1: Understand workload tolerance

    The batch job can handle interruptions and resume, so Spot Instances are suitable.

  2. Step 2: Choose cost-effective and reliable approach

    Setting a low max price saves money but risks interruptions; checkpointing allows resuming work safely.

  3. Step 3: Evaluate other options

    On-Demand and Reserved Instances cost more and don't leverage Spot savings; highest max price reduces savings.

  4. Final Answer:

    Request Spot Instances with a low max price and use checkpointing to save progress. -> Option C

  5. Quick Check:

    Interruptible job + low price + checkpointing = best cost savings [OK]
Hint: Use low max price + checkpointing for interruptible jobs [OK]
Common Mistakes:
  • Choosing On-Demand or Reserved ignoring cost savings
  • Setting max price too high losing savings
  • Not implementing checkpointing for interruptions
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