Objective 3 Section Recap

In this lesson, we’ve covered the core tasks for service registration and discovery with Consul. By understanding these five areas, you’ll be able to register, monitor, and query services reliably.

1. Interpreting a Service Registration

Every service registration file or API call includes several fields that tell Consul how to manage your service:

• ID: A unique identifier (defaults to the service name if not set).
• Name: Logical service name used for discovery.
• Tags: Custom labels for grouping or routing.
• Port: Listening port of your service.
• Address: Optional IP address (otherwise uses the agent’s IP).
• Checks: Health check definitions (see next section).

2. Registering a Service

You have three primary options to register a new service:

3. Adding Health Checks

Health checks ensure Consul only routes traffic to healthy instances. Common check types:

• HTTP

  {
    "http": "http://localhost:8080/health",
    "interval": "10s",
    "timeout": "1s"
  }
  

• TCP

  {
    "tcp": "localhost:8080",
    "interval": "10s"
  }
  

• Script

  {
    "script": "/usr/local/bin/check.sh",
    "interval": "15s"
  }
  

See the Consul Health Checks guide for advanced options.

4. Querying the Service Catalog

Verify your services and their health status using:

5. Prepared Queries & Failover

Prepared queries let you define advanced routing and failover rules:

1. Create a Prepared Query

   curl --request PUT --data @prepared.json http://localhost:8500/v1/query
   

2. Define Failover Strategy
   Include multiple service pools with weights or priorities.
3. Execute via API or DNS
   • HTTP: GET /v1/query/{query_id}/execute
   • DNS: dig @127.0.0.1 -p 8600 {query_name}.query.consul SRV

Prepared queries automatically reroute traffic when services become unhealthy.

Links & References

• Consul HTTP API – Service Registration
• Consul Health Checks
• Consul DNS Interface
• Consul Web UI