Configuring application health checks on a VM instance

If you do not have the Yandex Cloud CLI yet, install and initialize it.

The folder specified when creating the CLI profile is used by default. To change the default folder, use the yc config set folder-id <folder_ID> command. You can specify a different folder using the --folder-name or --folder-id parameter.

1. See the description of the CLI command for updating an instance group:

   yc compute instance-group update --help
   

2. Get a list of instance groups in the default folder:

   yc compute instance-group list
   

   Result:

   +----------------------+-----------------------+------+
   |          ID          |         NAME          | SIZE |
   +----------------------+-----------------------+------+
   | amc65sbgfqeq******** | first-instance-group  |    2 |
   +----------------------+-----------------------+------+
   

3. Select ID or NAME of the group you need, e.g., first-instance-group.

4. Get information about the instance group.

5. Create a YAML file with any name, e.g., group.yaml, and define the following based on the info you get:

   • Instance template.
   • Policies.
   • Service account ID.
   • Network load balancer specification, if required.

6. Add a health check specification to the file, e.g, for HTTP checks:

   ...
   health_checks_spec:
     health_check_specs:
       - http_options:
           port: 80
           path: /
         interval: 30s
         timeout: 10s
         unhealthy_threshold: 5
         healthy_threshold: 3
   ...
   

   Where:

   Key	Value
   health_check_specs	Health check specification
   http_options	Settings for HTTP health checks. Only HTTP/1.1 and lower are supported. If you want to use TCP, specify only the port number in the tcp_options property.
   port	Port in the range of 1 to 32767 Instance Groups will use to send check requests on.
   path	URL path Instance Groups will use to send HTTP check requests.
   interval	Interval between app health checks run by Instance Groups, in seconds.
   timeout	Response timeout in seconds. If you connected your group to a network load balancer, we recommend setting this parameter to a higher value than the one for the load balancer.
   unhealthy_threshold	Number of failed health checks required to consider a VM instance unhealthy. If you connected your group to a network load balancer, we recommend setting this parameter to a higher value than the one for the load balancer.
   healthy_threshold	Number of successful health checks required to consider a VM instance healthy. If you connected your group to a network load balancer, we recommend setting this parameter to a lower value than the one for the load balancer.

7. Update the instance group in the default folder:

   yc compute instance-group update --name first-group --file group.yaml
   

   Instance Groups will initiate instance group updating.