How to register multiple service instances in consul on one machine - go

Question

I have a consul running locally on a dev machine. I also have one golang service running on two different ports on the same machine. Is there a way to register them as one service but two instances in consul using golang API (for example, is it possible to specify the node name when registering)?

Answer 1

Here's a very basic example which registers two instances of a service named my-service. Each instance is configured to listen on a different port, 8080 and 8081 respectively.
The key thing to note is that the service instances are also registered with a unique service ID in order to disambiguate between instance A and instance B of my-service which are running on the same agent.
package main
import (
"fmt"
"github.com/hashicorp/consul/api"
)
func main() {
// Get a new client
client, err := api.NewClient(api.DefaultConfig())
if err != nil {
panic(err)
}
service_name := "my-service"
service_ports := [2]int{8080, 8081}
for idx, port := range service_ports {
svc_reg := &api.AgentServiceRegistration{
ID: fmt.Sprintf("%s-%d", service_name, idx),
Name: service_name,
Port: port,
}
client.Agent().ServiceRegister(svc_reg)
}
}
After running go mod init consul-register (or any module name), and executing the code with go run main.go, you can see the service has been registered in the catalog.
$ consul catalog services
consul
my-service
Both service instances are correctly being returned for service discovery queries over DNS or HTTP.
$ dig #127.0.0.1 -p 8600 -t SRV my-service.service.consul +short
1 1 8080 b1000.local.node.dc1.consul.
1 1 8081 b1000.local.node.dc1.consul.
$ curl localhost:8500/v1/health/service/my-service
[
{
"Node": {
"ID": "11113853-a8e0-5787-7482-538078db855a",
"Node": "b1000.local",
"Address": "127.0.0.1",
"Datacenter": "dc1",
"TaggedAddresses": {
"lan": "127.0.0.1",
"lan_ipv4": "127.0.0.1",
"wan": "127.0.0.1",
"wan_ipv4": "127.0.0.1"
},
"Meta": {
"consul-network-segment": ""
},
"CreateIndex": 11,
"ModifyIndex": 13
},
"Service": {
"ID": "my-service-0",
"Service": "my-service",
"Tags": [],
"Address": "",
"Meta": null,
"Port": 8080,
"Weights": {
"Passing": 1,
"Warning": 1
},
"EnableTagOverride": false,
"Proxy": {
"Mode": "",
"MeshGateway": {},
"Expose": {},
"TransparentProxy": {}
},
"Connect": {},
"CreateIndex": 14,
"ModifyIndex": 14
},
"Checks": [
{
"Node": "b1000.local",
"CheckID": "serfHealth",
"Name": "Serf Health Status",
"Status": "passing",
"Notes": "",
"Output": "Agent alive and reachable",
"ServiceID": "",
"ServiceName": "",
"ServiceTags": [],
"Type": "",
"Definition": {},
"CreateIndex": 11,
"ModifyIndex": 11
}
]
},
{
"Node": {
"ID": "11113853-a8e0-5787-7482-538078db855a",
"Node": "b1000.local",
"Address": "127.0.0.1",
"Datacenter": "dc1",
"TaggedAddresses": {
"lan": "127.0.0.1",
"lan_ipv4": "127.0.0.1",
"wan": "127.0.0.1",
"wan_ipv4": "127.0.0.1"
},
"Meta": {
"consul-network-segment": ""
},
"CreateIndex": 11,
"ModifyIndex": 13
},
"Service": {
"ID": "my-service-1",
"Service": "my-service",
"Tags": [],
"Address": "",
"Meta": null,
"Port": 8081,
"Weights": {
"Passing": 1,
"Warning": 1
},
"EnableTagOverride": false,
"Proxy": {
"Mode": "",
"MeshGateway": {},
"Expose": {},
"TransparentProxy": {}
},
"Connect": {},
"CreateIndex": 15,
"ModifyIndex": 15
},
"Checks": [
{
"Node": "b1000.local",
"CheckID": "serfHealth",
"Name": "Serf Health Status",
"Status": "passing",
"Notes": "",
"Output": "Agent alive and reachable",
"ServiceID": "",
"ServiceName": "",
"ServiceTags": [],
"Type": "",
"Definition": {},
"CreateIndex": 11,
"ModifyIndex": 11
}
]
}
]