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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.

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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).
A well-structured registration makes automated tooling and monitoring far easier to implement.

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2. Registering a Service

You have three primary options to register a new service:
MethodDescriptionExample
HTTP APISend a PUT request to the local Consul agent.curl --request PUT --data @svc.json http://localhost:8500/v1/agent/service/register
Config Directory FileDrop a JSON or HCL file into /etc/consul.d/ and reload the agent./etc/consul.d/my-service.hcl then consul reload
Direct CLI Config ReferencePoint the agent to a specific file and trigger a reload.consul agent -config-file=/path/to/service.json
After adding or modifying a file in the config directory, always run consul reload to apply changes without downtime.

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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.

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4. Querying the Service Catalog

Verify your services and their health status using:
InterfaceCommand / QueryNotes
DNSdig @127.0.0.1 -p 8600 web.service.consul SRVNative DNS lookup for service discovery
HTTP APIcurl http://localhost:8500/v1/catalog/service/webDetailed JSON output, including node info
Web UIBrowse http://localhost:8500/ui/servicesInteractive view of all registered services

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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.

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