How to Attach an Instance to a Vultr Load Balancer

1. Navigate to Network and click Load Balancers.

2. Click your target Load Balancer to open its Manage page.

3. Expand the Resources section.

4. Click the expand toggle next to the location where you want to attach instances, such as New York, US. The row displays a Primary badge on the primary location and the current instance count in the Instances column.

5. Under Instances in LOCATION, click Add Instances. The Add Instances in LOCATION panel opens on the right.

6. Select the checkbox next to each instance you want to attach. The panel lists each instance by name and UUID, and updates the Selected instances counter as you select them.

   Note

   The panel only lists instances deployed in the same location as the Load Balancer. Use the Search field to filter longer lists.

7. Click Save Changes.

8. Verify the attachment under Instances in LOCATION. The table lists each attached instance with its name, UUID, IPv4 address, and IPv6 address, and the Instances count on the location row increases to match.

Replace LOCATION with the geographic location of your Load Balancer, such as New York, US.

1. Send a GET request to the List Load Balancers endpoint and note the target Load Balancer's ID.

   console Copy

   $ curl "https://api.vultr.com/v2/load-balancers" \
       -X GET \
       -H "Authorization: Bearer ${VULTR_API_KEY}"
   

   Explain Code

2. Send a GET request to the List Instances endpoint and note your target instance's ID, ensuring it is in the same geographic region as the Load Balancer.

   console Copy

   $ curl "https://api.vultr.com/v2/instances" \
       -X GET \
       -H "Authorization: Bearer ${VULTR_API_KEY}"
   

   Explain Code

3. Send a PATCH request to the Update Load Balancer endpoint to attach instances to the target Load Balancer.

   console Copy

   $ curl "https://api.vultr.com/v2/load-balancers/{load-balancer-id}" \
       -X PATCH \
       -H "Authorization: Bearer ${VULTR_API_KEY}" \
       -H "Content-Type: application/json" \
       --data '{
           "instances": [
               "INSTANCE-1-ID",
               "INSTANCE-2-ID"
           ]
       }'
   

   Explain Code
   Note

   A newly created Load Balancer rejects this request with Load Balancer Nodes Still Activating... and a 422 status, even after the Get Load Balancer endpoint reports a status of active. Wait about a minute after creation, then send the request again.

4. Send a GET request to the Get Load Balancer endpoint to fetch the details of the target Load Balancer.

   console Copy

   $ curl "https://api.vultr.com/v2/load-balancers/{load-balancer-id}" \
       -X GET \
       -H "Authorization: Bearer ${VULTR_API_KEY}"
   

   Explain Code

1. List all available instances and note the target Load Balancer's ID.

   console Copy

   $ vultr-cli load-balancer list
   

   Explain Code

2. List all available instances and note your target instance's ID, ensuring it is in the same geographic region as the Load Balancer.

   console Copy

   $ vultr-cli instance list
   

   Explain Code

3. Update the target Load Balancer by attaching the new instances.

   console Copy

   $ vultr-cli load-balancer update LOAD-BALANCER-ID --instances "INSTANCE-1-ID,INSTANCE-2-ID,INSTANCE-3-ID"
   

   Explain Code

   Pass every instance ID as a single comma-separated value. Separating the IDs with spaces attaches only the first instance and discards the rest, while still reporting Load balancer has been updated.

4. Get the details of the target Load Balancer.

   console Copy

   $ vultr-cli load-balancer get LOAD-BALANCER-ID
   

   Explain Code

1. Open your Terraform configuration file for the existing Load Balancer.

2. Add the target instance IDs under the attached_instances attribute.

   terraform Copy

   resource "vultr_load_balancer" "lb" {
       # ...existing fields (region, forwarding_rules, health_check, etc.)
   
       attached_instances = [
           vultr_instance.web1.id,
           vultr_instance.web2.id
       ]
   }
   

   Explain Code

3. Apply the configuration and observe the following output:

   Apply complete! Resources: 0 added, 1 changed, 0 destroyed.