application

AKS Application

Terraform code for deploying an application.

Terraform documentation

For the list of requirement, inputs, outputs, resources... check the terraform module documentation.

Usage

module "web_application" {
  source = "git::https://github.com/DFE-Digital/terraform-modules.git//aks/application?ref=stable"

  name   = "web"
  is_web = true

  namespace    = var.namespace
  environment  = local.environment
  service_name = local.service_name

  cluster_configuration_map = module.cluster_data.configuration_map

  kubernetes_config_map_name = module.application_configuration.kubernetes_config_map_name
  kubernetes_secret_name     = module.application_configuration.kubernetes_secret_name

  docker_image = var.docker_image
}

module "worker_application" {
  source = "git::https://github.com/DFE-Digital/terraform-modules.git//aks/application?ref=stable"

  name   = "worker"
  is_web = false

  namespace    = var.namespace
  environment  = local.environment
  service_name = local.service_name

  cluster_configuration_map = module.cluster_data.configuration_map

  kubernetes_config_map_name = module.application_configuration.kubernetes_config_map_name
  kubernetes_secret_name     = module.application_configuration.kubernetes_secret_name

  docker_image = var.docker_image
  command      = ["bundle", "exec", "sidekiq"]
}

Health checks

For web applications, the default probe_path is set to /healthcheck. The probe can be turned off by setting the variable to null.

Rails

A simple one-line health check for a Rails application can be added to the routes.rb file:

get "/healthcheck", to: proc { [200, {}, ['OK']] }

For more complex health checks, the OkComputer Gem provides some advanced functionality, for example:

OkComputer.mount_at = "healthcheck"

OkComputer::Registry.register "database", OkComputer::ActiveRecordCheck.new

.NET

A simple one-line health check for an ASP.NET application can be added to the endpoints:

endpoints.MapGet("/healthcheck", async context => {
    await context.Response.WriteAsync("OK");
});

For more complex health checks, the ASP.NET Core Health Checks Middleware can be used, for example:

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddHealthChecks();

var app = builder.Build();

app.MapHealthChecks("/healthcheck/all");

Monitoring

If azure_enable_monitoring is true, it’s expected that the following resources already exist:

• A resource group named ${azure_resource_prefix}-${service_short}-mn-rg (where mn stands for monitoring and rg stands for resource group).
• A monitor action group named ${azure_resource_prefix}-${service_name} within the above resource group.

If enable_prometheus_monitoring is true then custom metrics are scraped for the application

Outputs

hostname

The hostname of the deployed application.

url

The URL of the deployed application.

probe_url

The URL of the deployed application combined with the probe path.