Automated DNS Failover for High-Availability AI systems

Question

Pulumi · Accepted Answer

To set up an automated DNS failover for high-availability AI systems, you can use various cloud providers that offer DNS management and failover solutions. In this case, I'll show you how to use AWS's services—specifically, Amazon Route 53 and Route 53 Recovery Control—to achieve an automated DNS failover setup.

Amazon Route 53 is a highly available and scalable DNS web service that can route end-user requests to infrastructure running in AWS (like EC2 instances, Elastic Load Balancing, or S3 buckets) and can also be used to route users to infrastructure outside of AWS. Route 53 Recovery Control is a set of capabilities of AWS's Route 53 service aimed at increasing the resilience and availability of your critical applications using various routing controls.

Here's what you'll do in the Pulumi program:
* Create a health check to monitor the endpoint of your AI system.
* Set up a failover routing policy in a hosted zone for a DNS record set.
* Implement safety rules using Route 53 Recovery Control where we define conditions that must be met for DNS failover to activate.

For the high-level approach, the program will:

1. Create a health check that ensures your primary AI system endpoint is healthy.
2. Set up a failover routing policy with Route 53 where the primary and secondary resources are defined (e.g., primary and secondary endpoints for your AI systems).
3. Use Recovery Control to set up safety rules that ensure failover will not happen accidentally or during false positives, providing a more robust and controlled failover process.

Now, let's write the Pulumi program in Python that will set up the automated DNS failover:

```python
import pulumi
import pulumi_aws as aws

# Assume that AI system endpoints are running and we have their IP addresses or domain names.
primary_ai_system_endpoint = "primary-ai-system.example.com"
secondary_ai_system_endpoint = "secondary-ai-system.example.com"

# Create a health check for the primary AI system.
primary_system_health_check = aws.route53.HealthCheck("primarySystemHealthCheck",
    fqdn=primary_ai_system_endpoint,
    failure_threshold=3,
    request_interval=30,
    type="HTTP",
    resource_path="/health",  # Path to the health endpoint of your service
)

# Create a Route 53 hosted zone for your domain if you don't already have one.
hosted_zone = aws.route53.Zone("hostedZone",
    name="example.com",
)

# Create DNS record sets for primary and secondary endpoints.
primary_dns_record = aws.route53.Record("primaryDnsRecord",
    zone_id=hosted_zone.id,
    name=f"ai-system.example.com",
    type="A",
    failover_routing_policies=[
        aws.route53.RecordFailoverRoutingPolicyArgs(
            type="PRIMARY",
        )
    ],
    health_check_id=primary_system_health_check.id,
    set_identifier="primary",
    records=[primary_ai_system_endpoint],
    ttl=60,
)

secondary_dns_record = aws.route53.Record("secondaryDnsRecord",
    zone_id=hosted_zone.id,
    name="ai-system.example.com",
    type="A",
    failover_routing_policies=[
        aws.route53.RecordFailoverRoutingPolicyArgs(
            type="SECONDARY",
        )
    ],
    set_identifier="secondary",
    records=[secondary_ai_system_endpoint],
    ttl=60,
)

# Configure safety rule in Route 53 Recovery Control.
# This is a simplified rule that can be expanded to meet more complex requirements.
safety_rule = aws.route53recoverycontrol.SafetyRule("safetyRule",
    rule_config=aws.route53recoverycontrol.SafetyRuleRuleConfigArgs(
        type="AND",  # Combine checks, you can specify other types like 'OR' or 'NOT'
        inverted=False,  # Set to True if you want the check to ensure the endpoint is not available
        threshold=1,  # The number of controls that must be "ON" for the safety rule to apply
    ),
    wait_period_ms=5000,  # Time to wait before initiating a failover
    control_panel_arn="{control_panel_arn}",  # Replace with your control panel ARN
    name="mySafetyRule",
)

pulumi.export('primaryDnsRecord', primary_dns_record.fqdn)
pulumi.export('secondaryDnsRecord', secondary_dns_record.fqdn)
```

Let's break down what the program is doing:
1. **Health Check Setup**: We're creating a health check for the primary endpoint to continuously monitor its responsiveness.
2. **Hosted Zone Creation**: A hosted zone in Route 53 is initialized if we don't already have one for the `example.com` domain.
3. **Primary and Secondary DNS**: We configure DNS records for both the primary and secondary endpoints. These records use a failover routing policy where Route 53 directs traffic to the primary and would automatically switch to the secondary, should the health check fail.
4. **Safety Rule Configuration**: We set up a safety rule to manage when failover should occur, preventing false positives and ensuring that failover only happens under defined circumstances.
5. **Exports**: We export the fully qualified domain name (FQDN) of the primary and secondary DNS records for external reference.

Please replace `{control_panel_arn}` with the actual ARN of your control panel in Route 53 Recovery Control, and make sure that the FQDNs and endpoints match your actual AI service endpoints. The `resource_path` in the health check should also accurately point to the health check endpoint of your service.