AWS Load Balancer AZ Check

Validates the availability of target availability zone(s) in the given ALB or CLB.

Infrastructure type

• Kubernetes

Use cases

AWS Load Balancer AZ Check probe helps you:

• Verify load balancer AZ configuration during AZ failures
• Validate traffic distribution across availability zones
• Monitor load balancer health during network chaos experiments
• Ensure multi-AZ redundancy is maintained

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Overview

This probe uses the AWS CLI to query load balancer configuration and validates that the specified availability zones are properly configured and available. It supports both Application Load Balancers (ALB) and Classic Load Balancers (CLB).

Probe type

Command Probe

Prerequisites

• Kubernetes cluster with chaos infrastructure installed
• AWS credentials configured with appropriate IAM permissions:
  • elasticloadbalancing:DescribeLoadBalancers
  • elasticloadbalancing:DescribeLoadBalancerAttributes
  • elasticloadbalancing:DescribeTargetHealth (for ALB)
• Network connectivity to AWS API endpoints
• Target load balancer should exist in the specified region

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Probe properties

Command

healthchecks -name aws-lb-az

Comparator

Type	Criteria	Value
string	contains	[Pass]

The probe passes when the command output contains [Pass], indicating the specified availability zones are configured in the load balancer.

Environment variables

Variable	Description	Required	Default
LOAD_BALANCER_ARN	ARN of the ALB to check (e.g., arn:aws:elasticloadbalancing:us-east-1:123456789012:loadbalancer/app/my-alb/1234567890abcdef). Required for ALB.	No*	-
LOAD_BALANCER_NAME	Name of the CLB to check (e.g., my-classic-lb). Required for CLB.	No*	-
REGION	AWS region where the load balancer is located (e.g., us-east-1, eu-west-2).	Yes	-
ZONES	Comma-separated list of Availability Zones to check (e.g., us-east-1a,us-east-1b,us-east-1c).	Yes	-

Note: Either LOAD_BALANCER_ARN (for ALB) or LOAD_BALANCER_NAME (for CLB) must be provided.

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Run properties

Property	Description	Type	Default
timeout	Maximum time to wait for the probe to complete (e.g., 30s, 1m, 5m)	String	300s
interval	Time between probe executions (e.g., 5s, 30s, 1m)	String	10s
attempt	Number of retry attempts before marking the probe as failed	Integer	1
pollingInterval	Time between retry attempts (e.g., 1s, 5s, 10s)	String	-
initialDelay	Initial delay before starting the probe (e.g., 0s, 10s, 30s)	String	-
stopOnFailure	Stop the experiment if the probe fails	Boolean	false
verbosity	Log verbosity level (info, debug, trace)	String	-

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Probe definition

You can define this probe in your chaos experiment as follows:

For Application Load Balancer (ALB)

probe:
  - name: "alb-az-availability-check"
    type: "cmdProbe"
    mode: "Continuous"
    cmdProbe/inputs:
      command: "healthchecks -name aws-lb-az"
      comparator:
        type: "string"
        criteria: "contains"
        value: "[Pass]"
      env:
        - name: LOAD_BALANCER_ARN
          value: "arn:aws:elasticloadbalancing:us-east-1:123456789012:loadbalancer/app/my-alb/1234567890abcdef"
        - name: REGION
          value: "us-east-1"
        - name: ZONES
          value: "us-east-1a,us-east-1b,us-east-1c"
    runProperties:
      timeout: 300s
      interval: 10s
      attempt: 1
      stopOnFailure: false

For Classic Load Balancer (CLB)

probe:
  - name: "clb-az-availability-check"
    type: "cmdProbe"
    mode: "Edge"
    cmdProbe/inputs:
      command: "healthchecks -name aws-lb-az"
      comparator:
        type: "string"
        criteria: "contains"
        value: "[Pass]"
      env:
        - name: LOAD_BALANCER_NAME
          value: "my-classic-load-balancer"
        - name: REGION
          value: "eu-west-1"
        - name: ZONES
          value: "eu-west-1a,eu-west-1b"
    runProperties:
      timeout: 60s
      interval: 5s
      attempt: 3
      pollingInterval: 2s