feat(CustomMetrics): Allow Different App to Send Custom Metrics

[asalan316]

Previously, only the application sending custom metrics to the autoscaler could be scaled.

The new feature enables users to scale an application based on custom metrics sent by an arbitrary app (Custom Metrics Producer), This is achievable if:

• Both applications are bound to same application autoscaler instance
• The application to scale has the "metric_submission_strategy.allow_from" set to bound_app during the binding process

How It Works

To enable this feature, specify the metric_submission_strategy.allow_from : "bound_app" parameter in the configuration object during the binding process with the application to be scaled (as shown below)

Binding Configuration (aka.scaling policy)

{
  "configuration": {
    "custom_metrics": {
      "metric_submission_strategy": {
        "allow_from": "bound_app"
      }
    }
  },
  "instance_max_count":4,
  "instance_min_count":1,
  "scaling_rules":[
    {
      "metric_type":"test_metric",
      "threshold":500,
      "operator":">",
      "adjustment":"+1"
    }, {
      "metric_type":"test_metric",
      "threshold":100,
      "operator":"<",
      "adjustment":"-1"
    }
  ]
}

Bind to Applications

# Bind autoscaler to application to scale

cf bind-service  app-to-scale  autosocaler -c <binding Configuration.json>

# Bind autoscaler to custom metrics producer app

cf bind-service  custom-metrics-producer-app  autosocaler

Other Changes

• Introduced additional database bindingDB in metricsforwarder service to retrieve binding information
• Added New Database schema to validate custom metrics strategy - allowed values are bound_app and same_app (default)
• Introduced a configuration structure to differentiate between policy and binding configurations

[sonarcloud]

Quality Gate failed

Failed conditions
5.3% Duplication on New Code (required ≤ 3%)

See analysis details on SonarCloud