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App Insights - Alerts

Overview

Azure Application Insights allows you to monitor your application and send you alerts when it is either unavailable, experiencing failures, or suffering from performance issues.

Application Insights Metric Alerts (Microsoft.Insights/metricAlerts)

Builder Keywords

Keyword	Purpose
name	Sets the name of Alert.
description	Sets the description of the alert.
frequency	How often the metric alert is evaluated
window	The period of time that is used to monitor alert activity based on the threshold.
severity	Alert severity
add_linked_resource	Add target resource on which the alert is created/updated.
add_linked_resources	Add the target resources on which the alert is created/updated.
single_resource_multiple_metric_criteria	The rule criteria that defines the conditions of the alert rule.
single_resource_multiple_custom_metric_criteria	The rule criteria that defines the conditions of the alert rule based on Application Insights custom metric or metric with custom namespace. Metric validation is disabled for such criteria, so it is possible to create an alert that watches metrics not yet emitted. More details are available here.
multiple_resource_multiple_metric_criteria	The rule criterias that defines the conditions of the alert rule.
webtest_location_availability_criteria	The rule criteria that defines the conditions of the alert rule. AppInsightsId * WebTestId * FailedLocationCount
add_action	Add an action that are performed when the alert rule becomes active.

More detailed documentation: https://docs.microsoft.com/en-us/azure/templates/microsoft.insights/metricalerts?tabs=json#metricalertproperties

Example

Virtual machine alert:

let vm = vm { name "foo"; username "foo" }
let vmAlert = alert { 
    name "myVmAlert2"
    description "Alert if VM CPU goes over 80% for 15 minutes"
    frequency (System.TimeSpan.FromMinutes(5.0) |> IsoDateTime.OfTimeSpan)
    window (System.TimeSpan.FromMinutes(15.0) |> IsoDateTime.OfTimeSpan)
    add_linked_resource vm
    severity AlertSeverity.Warning
    single_resource_multiple_metric_criteria [
            {   MetricNamespace = vm.ResourceId.Type
                MetricName = MetricsName.PercentageCPU
                Threshold = 80
                Comparison = GreaterThan
                Aggregation = Average
            }]
}

For the metric names and their aggregations, there is a huge list of options: https://docs.microsoft.com/en-us/azure/azure-monitor/essentials/metrics-supported

Database alert:

let myAlert = alert { 
        name "myDbAlert"
        description "Alert if DB DTU goes over 85% for 5 minutes"
        frequency (System.TimeSpan.FromMinutes(1.0) |> IsoDateTime.OfTimeSpan)
        window (System.TimeSpan.FromMinutes(5.0) |> IsoDateTime.OfTimeSpan)
        add_linked_resource resId
        severity AlertSeverity.Error
        single_resource_multiple_metric_criteria [
                {   MetricNamespace = resId.ResourceId.Type
                    MetricName = MetricsName.SQL_DB_DTU
                    Threshold = 85
                    Comparison = GreaterThan
                    Aggregation = Average
                }]
    }

Website down alert:

let ai = appInsights { name "ai" }
let webtest = availabilityTest { ... } 
let aiId, webId = (ai :> IBuilder).ResourceId |> Managed, 
                    (webtest :> IBuilder).ResourceId |> Managed
let webAlert = alert { 
    name "myWebAlert"
    description "Alert if website is failing 5 mins on 3 locations"
    frequency (System.TimeSpan.FromMinutes(1.0) |> IsoDateTime.OfTimeSpan)
    window (System.TimeSpan.FromMinutes(5.0) |> IsoDateTime.OfTimeSpan)
    add_linked_resources [aiId; webId]
    severity AlertSeverity.Warning
    webtest_location_availability_criteria (aiId.ResourceId, webId.ResourceId, 3)
}

Custom metric alert based on Azure Application Insights:

let ai = appInsights { name "ai" }

let customMetricAlert = alert {
    name "customMetricAlert"
    description "My Custom Metric Alert Description"
    frequency (System.TimeSpan.FromMinutes(1.0) |> IsoDateTime.OfTimeSpan)
    window (System.TimeSpan.FromMinutes(5.0) |> IsoDateTime.OfTimeSpan)
    add_linked_resource ai
    severity AlertSeverity.Error
    single_resource_multiple_custom_metric_criteria [
        {
            MetricNamespace = None
            MetricName = Insights.MetricsName "MyCustomMetric"
            Threshold = 0
            Comparison = GreaterThan
            Aggregation = Maximum
        }
    ]
}

Custom metric alert with custom metric namespace:

let ai = appInsights { name "ai" }

let customMetricAlert = alert {
    name "customMetricAlert"
    description "My Custom Metric Alert Description"
    frequency (System.TimeSpan.FromMinutes(1.0) |> IsoDateTime.OfTimeSpan)
    window (System.TimeSpan.FromMinutes(5.0) |> IsoDateTime.OfTimeSpan)
    add_linked_resource ai
    severity AlertSeverity.Error
    single_resource_multiple_custom_metric_criteria [
        {
            MetricNamespace = Some (ResourceType("MyCustomNamespace", ""))
            MetricName = Insights.MetricsName "MyCustomMetric"
            Threshold = 0
            Comparison = GreaterThan
            Aggregation = Maximum
        }
    ]
}