Monitor Azure Application Gateway

  • Article

This article describes:

  • The types of monitoring data you can collect for this service.
  • How to analyze that data.

Note

If you're already familiar with this service and/or Azure Monitor and just want to know how to analyze monitoring data, see the Analyze section near the end of this article.

When you have critical applications and business processes that rely on Azure resources, you need to monitor and get alerts for your system. The Azure Monitor service collects and aggregates metrics and logs from every component of your system. Azure Monitor provides you with a view of availability, performance, and resilience, and notifies you of issues. You can use the Azure portal, PowerShell, Azure CLI, REST API, or client libraries to set up and view monitoring data.

https://docs.azure.cn/azure-monitor/logs/logs-ingestion-api-overview

Insights

Some services in Azure have a built-in monitoring dashboard in the Azure portal that provides a starting point for monitoring your service. These dashboards are called insights, and you can find them in the Insights Hub of Azure Monitor in the Azure portal.

Azure Monitor Network Insights provides a comprehensive view of health and metrics for all deployed network resources including Application Gateway, without requiring any configuration. For more information, see Azure Monitor Network Insights.

Resource types

Azure uses the concept of resource types and IDs to identify everything in a subscription. Azure Monitor similarly organizes core monitoring data into metrics and logs based on resource types, also called namespaces. Different metrics and logs are available for different resource types. Your service might be associated with more than one resource type.

Resource types are also part of the resource IDs for every resource running in Azure. For example, one resource type for a virtual machine is Microsoft.Compute/virtualMachines. For a list of services and their associated resource types, see Resource providers.

For more information about the resource types for Application Gateway, see Application Gateway monitoring data reference.

Data storage

For Azure Monitor:

  • Metrics data is stored in the Azure Monitor metrics database.
  • Log data is stored in the Azure Monitor logs store. Log Analytics is a tool in the Azure portal that can query this store.
  • The Azure activity log is a separate store with its own interface in the Azure portal.
  • You can optionally route metric and activity log data to the Azure Monitor logs database store so you can query the data and correlate it with other log data using Log Analytics.

For detailed information on how Azure Monitor stores data, see Azure Monitor data platform.

For Application Gateway, resource-specific mode creates three tables:

  • AGWAccessLogs
  • AGWPerformanceLogs
  • AGWFirewallLogs

Note

The resource specific option is currently available in all public regions.

Existing users can continue using Azure Diagnostics, or can opt for dedicated tables by switching the toggle in Diagnostic settings to Resource specific, or to Dedicated in API destination.Dual mode isn't possible. The data in all the logs can either flow to Azure Diagnostics, or to dedicated tables. However, you can have multiple diagnostic settings where one data flow is to azure diagnostic and another is using resource specific at the same time.

Selecting the destination table in Log analytics: All Azure services eventually use the resource-specific tables. As part of this transition, you can select Azure diagnostic or resource specific table in the diagnostic setting using a toggle button. The toggle is set to Resource specific by default and in this mode, logs for new selected categories are sent to dedicated tables in Log Analytics, while existing streams remain unchanged. See the following example.

Screenshot of the resource ID for application gateway in the portal.

Workspace Transformations: Opting for the Resource specific option allows you to filter and modify your data before workspace transformations ingests it. This approach provides granular control, allowing you to focus on the most relevant information from the logs there by reducing data costs and enhancing security.

For detailed instructions on setting up workspace transformations, see Tutorial: Add a workspace transformation to Azure Monitor Logs by using the Azure portal.

Azure Monitor platform metrics

Azure Monitor provides platform metrics for most services. These metrics are:

  • Individually defined for each namespace.
  • Stored in the Azure Monitor time-series metrics database.
  • Lightweight and capable of supporting near real-time alerting.
  • Used to track the performance of a resource over time.

Collection: Azure Monitor collects platform metrics automatically. No configuration is required.

Routing: You can also usually route platform metrics to Azure Monitor logs / Log Analytics so you can query them with other log data. For more information, see the Metrics diagnostic setting. For how to configure diagnostic settings for a service, see Create diagnostic settings in Azure Monitor.

For a list of all metrics it's possible to gather for all resources in Azure Monitor, see Supported metrics in Azure Monitor.

The Overview page in the Azure portal for each Application Gateway includes the following metrics:

  • Sum Total Requests
  • Sum Failed Requests
  • Sum Response Status by HttpStatus
  • Sum Throughput
  • Sum CurrentConnections
  • Avg Healthy Host Count By BackendPool HttpSettings
  • Avg Unhealthy Host Count By BackendPool HttpSettings

For a list of available metrics for Azure Application Gateway, see Application Gateway monitoring data reference.

For available Web Application Firewall (WAF) metrics, see Application Gateway WAF v2 metrics and Application Gateway WAF v1 metrics.

Azure Monitor resource logs

Resource logs provide insight into operations that were done by an Azure resource. Logs are generated automatically, but you must route them to Azure Monitor logs to save or query them. Logs are organized by category. A given namespace might have multiple resource log categories.

Collection: Resource logs aren't collected and stored until you create a diagnostic setting and route the logs to one or more locations. When you create a diagnostic setting, you specify which categories of logs to collect. There are multiple ways to create and maintain diagnostic settings, including the Azure portal, programmatically, and though Azure Policy.

Routing: The suggested default is to route resource logs to Azure Monitor Logs so you can query them with other log data. Other locations such as Azure Storage, Azure Event Hubs, and certain Azure monitoring partners are also available. For more information, see Azure resource logs and Resource log destinations.

For detailed information about collecting, storing, and routing resource logs, see Diagnostic settings in Azure Monitor.

For a list of all available resource log categories in Azure Monitor, see Supported resource logs in Azure Monitor.

All resource logs in Azure Monitor have the same header fields, followed by service-specific fields. The common schema is outlined in Azure Monitor resource log schema.

Data in Azure Monitor Logs is stored in tables where each table has its own set of unique properties.

See Application Gateway monitoring data reference for:

  • A list of the types of resource logs collected for Application Gateway.
  • A list of the tables used by Azure Monitor Logs and queryable by Log Analytics.
  • The available resource log categories, their associated Log Analytics tables, and the log schemas for Application Gateway.

Azure activity log

The activity log contains subscription-level events that track operations for each Azure resource as seen from outside that resource; for example, creating a new resource or starting a virtual machine.

Collection: Activity log events are automatically generated and collected in a separate store for viewing in the Azure portal.

Routing: You can send activity log data to Azure Monitor Logs so you can analyze it alongside other log data. Other locations such as Azure Storage, Azure Event Hubs, and certain Azure monitoring partners are also available. For more information on how to route the activity log, see Overview of the Azure activity log.

Analyze monitoring data

There are many tools for analyzing monitoring data.

Azure Monitor tools

Azure Monitor supports the following basic tools:

Tools that allow more complex visualization include:

  • Dashboards that let you combine different kinds of data into a single pane in the Azure portal.
  • Workbooks, customizable reports that you can create in the Azure portal. Workbooks can include text, metrics, and log queries.
  • Power BI, a business analytics service that provides interactive visualizations across various data sources. You can configure Power BI to automatically import log data from Azure Monitor to take advantage of these visualizations.

Analyzing Access logs through GoAccess

We published a Resource Manager template that installs and runs the popular GoAccess log analyzer for Application Gateway Access Logs. GoAccess provides valuable HTTP traffic statistics such as Unique Visitors, Requested Files, Hosts, Operating Systems, Browsers, HTTP Status codes and more. For more details, please see the Readme file in the Resource Manager template folder in GitHub.

Azure Monitor export tools

You can get data out of Azure Monitor into other tools by using the following methods:

To get started with the REST API for Azure Monitor, see Azure monitoring REST API walkthrough.

Kusto queries

You can analyze monitoring data in the Azure Monitor Logs / Log Analytics store by using the Kusto query language (KQL).

Important

When you select Logs from the service's menu in the portal, Log Analytics opens with the query scope set to the current service. This scope means that log queries will only include data from that type of resource. If you want to run a query that includes data from other Azure services, select Logs from the Azure Monitor menu. See Log query scope and time range in Azure Monitor Log Analytics for details.

For a list of common queries for any service, see the Log Analytics queries interface.

The following examples show some useful queries for Application Gateway.

// Requests per hour 
// Count of the incoming requests on the Application Gateway. 
// To create an alert for this query, click '+ New alert rule'
AzureDiagnostics
| where ResourceType == "APPLICATIONGATEWAYS" and OperationName == "ApplicationGatewayAccess"
| summarize AggregatedValue = count() by bin(TimeGenerated, 1h), _ResourceId
| render timechart 

// Failed requests per hour 
// Count of requests to which Application Gateway responded with an error. 
// To create an alert for this query, click '+ New alert rule'
AzureDiagnostics
| where ResourceType == "APPLICATIONGATEWAYS" and OperationName == "ApplicationGatewayAccess" and httpStatus_d > 399
| summarize AggregatedValue = count() by bin(TimeGenerated, 1h), _ResourceId
| render timechart

// Top 10 Client IPs 
// Count of requests per client IP. 
AzureDiagnostics
| where ResourceType == "APPLICATIONGATEWAYS" and OperationName == "ApplicationGatewayAccess"
| summarize AggregatedValue = count() by clientIP_s
| top 10 by AggregatedValue

// Errors by user agent 
// Number of errors by user agent. 
// To create an alert for this query, click '+ New alert rule'
AzureDiagnostics
| where ResourceType == "APPLICATIONGATEWAYS" and OperationName == "ApplicationGatewayAccess" and httpStatus_d > 399
| summarize AggregatedValue = count() by userAgent_s, _ResourceId
| sort by AggregatedValue desc

Alerts

Azure Monitor alerts proactively notify you when specific conditions are found in your monitoring data. Alerts allow you to identify and address issues in your system before your customers notice them. For more information, see Azure Monitor alerts.

There are many sources of common alerts for Azure resources. For examples of common alerts for Azure resources, see Sample log alert queries. The Azure Monitor Baseline Alerts (AMBA) site provides key alert metrics, dashboards, and guidelines for Azure Landing Zone (ALZ) scenarios.

The common alert schema standardizes the consumption of Azure Monitor alert notifications. For more information, see Common alert schema.

Types of alerts

You can alert on any metric or log data source in the Azure Monitor data platform. There are many different types of alerts depending on the services you're monitoring and the monitoring data you're collecting. Different types of alerts have various benefits and drawbacks. For more information, see Choose the right monitoring alert type.

The following list describes the types of Azure Monitor alerts you can create:

  • Metric alerts evaluate resource metrics at regular intervals. Metrics can be platform metrics, custom metrics, logs from Azure Monitor converted to metrics, or Application Insights metrics. Metric alerts can also apply multiple conditions and dynamic thresholds.
  • Log alerts allow users to use a Log Analytics query to evaluate resource logs at a predefined frequency.
  • Activity log alerts trigger when a new activity log event occurs that matches defined conditions. Resource Health alerts and Service Health alerts are activity log alerts that report on your service and resource health.

You can also create the following types of alerts for some Azure services:

  • Smart detection alerts on an Application Insights resource automatically warn you of potential performance problems and failure anomalies in your web application. You can migrate smart detection on your Application Insights resource to create alert rules for the different smart detection modules.
  • Prometheus alerts alert on Prometheus metrics stored in Azure Monitor managed services for Prometheus . The alert rules are based on the PromQL open-source query language. Your service may not support this type of alert. Currently, Prometheus is used on a limited set of services with a guest operating system, such as Azure Virtual Machine and Azure Container Instances.
  • Recommended alert rules are available out-of-box for some Azure resources, including virtual machines, Azure Kubernetes Service (AKS) resources, and Log Analytics workspaces.

Monitor multiple resources

You can monitor at scale by applying the same metric alert rule to multiple resources of the same type that exist in the same Azure region. Individual notifications are sent for each monitored resource. For supported Azure services and clouds, see Monitor multiple resources with one alert rule.

Note

If you're creating or running an application that runs on your service, Azure Monitor application insights might offer more types of alerts.

To configure alerts using ARM templates, see Configure Azure Monitor alerts.

Application Gateway alert rules

The following table lists some suggested alert rules for Application Gateway. These alerts are just examples. You can set alerts for any metric, log entry, or activity log entry listed in the Application Gateway monitoring data reference.

Application Gateway v2

Alert type Condition Description
Metric Compute Unit utilization crosses 75% of average usage Compute unit is the measure of compute utilization of your Application Gateway. Check your average compute unit usage in the last one month and set alert if it crosses 75% of it.
Metric Capacity Unit utilization crosses 75% of peak usage Capacity units represent overall gateway utilization in terms of throughput, compute, and connection count. Check your maximum capacity unit usage in the last one month and set alert if it crosses 75% of it.
Metric Unhealthy host count crosses threshold Indicates number of backend servers that application gateway is unable to probe successfully. This alert catches issues where Application gateway instances are unable to connect to the backend. Alert if this number goes above 20% of backend capacity.
Metric Response status (4xx, 5xx) crosses threshold When Application Gateway response status is 4xx or 5xx. There could be occasional 4xx or 5xx response seen due to transient issues. You should observe the gateway in production to determine static threshold or use dynamic threshold for the alert.
Metric Failed requests crosses threshold When Failed requests metric crosses threshold. You should observe the gateway in production to determine static threshold or use dynamic threshold for the alert.
Metric Backend last byte response time crosses threshold Indicates the time interval between start of establishing a connection to backend server and receiving the last byte of the response body. Create an alert if the backend response latency is more that certain threshold from usual.
Metric Application Gateway total time crosses threshold This value is the interval from the time when Application Gateway receives the first byte of the HTTP request to the time when the last response byte has been sent to the client. Should create an alert if the backend response latency is more that certain threshold from usual.

Application Gateway v1

Alert type Condition Description
Metric CPU utilization crosses 80% Under normal conditions, CPU usage shouldn't regularly exceed 90%. This situation can cause latency in the websites hosted behind the Application Gateway and disrupt the client experience.
Metric Unhealthy host count crosses threshold Indicates the number of backend servers that Application Gateway is unable to probe successfully. This alert catches issues where the Application Gateway instances are unable to connect to the backend. Alert if this number goes above 20% of backend capacity.
Metric Response status (4xx, 5xx) crosses threshold When Application Gateway response status is 4xx or 5xx. There could be occasional 4xx or 5xx response seen due to transient issues. You should observe the gateway in production to determine static threshold or use dynamic threshold for the alert.
Metric Failed requests crosses threshold When failed requests metric crosses a threshold. You should observe the gateway in production to determine static threshold or use dynamic threshold for the alert.

Azure Monitor alerts proactively notify you when important conditions are found in your monitoring data. They allow you to identify and address issues in your system before your customers notice them. You can set alerts on metrics, logs, and the activity log. Different types of alerts have benefits and drawbacks.

If you're creating or running an application that uses Application Gateway, Azure Monitor Application Insights can offer other types of alerts.

Advisor recommendations

If critical conditions or imminent changes occur during resource operations, an alert displays on the Overview page in the portal.

You can find more information and recommended fixes for the alert in Advisor recommendations under Monitoring. During normal operations, no advisor recommendations display.

For more information on Azure Advisor, see Azure Advisor overview.

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