Monitoring the performance of a Compute Engine instance in GCP can be done using Cloud Monitoring, which provides key metrics such as CPU usage, disk I/O, and network usage. Here’s how to monitor the performance using GCP Console, gcloud CLI, and Terraform:

1. Using GCP Console:

a. Go to the GCP Console: https://console.cloud.google.com/

b. Navigate to Monitoring > Metrics Explorer.

c. In the “Find resource type and metric” field, enter “compute.googleapis.com/instance/” and select a metric, such as “CPU utilization.”

d. Under “Filter,” select “instance_name” and enter the name of the Compute Engine instance you want to monitor.

e. Configure the aggregation settings, such as the alignment period and reducer function, as needed.

f. The chart will display the selected metric for the instance over time. You can add additional metrics or create custom dashboards for better monitoring.

2. Using gcloud CLI:

a. Install the Google Cloud SDK and configure authentication: https://cloud.google.com/sdk/docs/install

b. Use the Monitoring API to retrieve metrics for a specific instance. For example, to get CPU utilization:

gcloud monitoring read 'compute.googleapis.com/instance/cpu/utilization' --start="START_TIME" --end="END_TIME" --filter='metric.labels.instance_name=INSTANCE_NAME' --zone=ZONE

Replace START_TIME, END_TIME, INSTANCE_NAME, and ZONE with appropriate values. The command will return the metric data in JSON format.

3. Using Terraform:

Terraform does not provide a direct way to monitor Compute Engine instance performance. However, you can use Terraform to create a Cloud Monitoring dashboard that displays key metrics for your instances. Here’s an example of creating a dashboard with CPU utilization:

resource "google_monitoring_dashboard" "example" {
  project = "PROJECT_ID"
  dashboard_json = jsonencode({
    displayName = "Example Dashboard"
    gridLayout = {
      columns = "2"
      widgets = [
        {
          title = "CPU Utilization"
          xyChart = {
            dataSets = [
              {
                timeSeriesQuery = {
                  filter = "metric.type=\"compute.googleapis.com/instance/cpu/utilization\" resource.type=\"gce_instance\""
                  unitOverride = "1"
                }
                plotType = "LINE"
              }
            ]
            timeshiftDuration = "0s"
            yAxis = {
              label = "y1Axis"
              scale = "LINEAR"
            }
            chartOptions = {
              mode = "COLOR"
            }
          }
        }
      ]
    }
  })
}

Replace PROJECT_ID with your GCP project ID.

b. Run the following commands to apply the changes:

terraform init
terraform plan
terraform apply

This will create a Cloud Monitoring dashboard with a chart displaying the CPU utilization of your Compute Engine instances. You can customize the dashboard by adding more metrics or modifying the layout.

For more advanced monitoring and alerting, you can also create alerting policies using Terraform to notify you when certain conditions are met, such as high CPU utilization.