Metrics for Application Gateway

8/29/2019
6 minutes to read

Application Gateway publishes data points, called metrics, to Azure Monitor for the performance of your Application Gateway and backend instances. These metrics are numerical values in an ordered set of time-series data that describe some aspect of your application gateway at a particular time. If there are requests flowing through the Application Gateway, it measures and sends its metrics in 60-second intervals. If there are no requests flowing through the Application Gateway or no data for a metric, the metric is not reported. For more information, see Azure Monitor metrics.

Metrics supported by Application Gateway V2 SKU

Timing metrics

The following metrics related to timing of the request and response are available. By analyzing these metrics, you can determine whether the slowdown in application in due to the WAN, the Application Gateway, the network between the Application Gateway and the backend, or the application performance.

Client RTT

Average round trip time between clients and Application Gateway. This metric indicates how long it takes to establish connections and return acknowledgments.
Application gateway total time

Average time that it takes for a request to be processed and its response to be sent. This is calculated as average of the interval from the time when Application Gateway receives the first byte of an HTTP request to the time when the response send operation finishes. It's important to note that this usually includes the Application Gateway processing time, time that the request and response packets are traveling over the network and the time the backend server took to respond.
Backend connect time

Time spent establishing a connection with a backend server.
Backend first byte response time

Time interval between start of establishing a connection to backend server and receiving the first byte of the response header, approximating processing time of backend server
Backend last byte response time

Time interval between start of establishing a connection to backend server and receiving the last byte of the response body

Application Gateway metrics

For Application Gateway, the following metrics are available:

Bytes received

Count of bytes received by the Application Gateway from the clients
Bytes sent

Count of bytes sent by the Application Gateway to the clients
Client TLS protocol

Count of TLS and non-TLS requests initiated by the client that established connection with the Application Gateway. To view TLS protocol distribution, filter by the dimension TLS Protocol.
Current capacity units

Count of capacity units consumed. Capacity units measure consumption-based cost that is charged in addition to the fixed cost. There are three determinants to capacity unit - compute unit, persistent connections and throughput. Each capacity unit is composed of at most: 1 compute unit, or 2500 persistent connections, or 2.22-Mbps throughput.
Current compute units

Count of processor capacity consumed. Factors affecting compute unit are TLS connections/sec, URL Rewrite computations, and WAF rule processing.
Current connections

Count of current connections established with Application Gateway
Failed Requests

Count of failed requests that Application Gateway has served. The request count can be further filtered to show count per each/specific backend pool-http setting combination.
Response Status

HTTP response status returned by Application Gateway. The response status code distribution can be further categorized to show responses in 2xx, 3xx, 4xx, and 5xx categories.
Throughput

Number of bytes per second the Application Gateway has served
Total Requests

Count of successful requests that Application Gateway has served. The request count can be further filtered to show count per each/specific backend pool-http setting combination.
Web Application Firewall matched rules
Web Application Firewall triggered rules

Backend metrics

For Application Gateway, the following metrics are available:

Backend response status

Count of HTTP response status codes returned by the backends. This does not include any response codes generated by the Application Gateway. The response status code distribution can be further categorized to show responses in 2xx, 3xx, 4xx, and 5xx categories.
Healthy host count

The number of backends that are determined healthy by the health probe. You can filter on a per backend pool basis to show healthy/unhealthy hosts in a specific backend pool.
Unhealthy host count

The number of backends that are determined unhealthy by the health probe. You can filter on a per backend pool basis to show unhealthy hosts in a specific backend pool.

Metrics supported by Application Gateway V1 SKU

Application Gateway metrics

For Application Gateway, the following metrics are available:

Current connections

Count of current connections established with Application Gateway
Failed Requests

Count of failed requests that Application Gateway has served. The request count can be further filtered to show count per each/specific backend pool-http setting combination.
Response Status

HTTP response status returned by Application Gateway. The response status code distribution can be further categorized to show responses in 2xx, 3xx, 4xx, and 5xx categories.
Throughput

Number of bytes per second the Application Gateway has served
Total Requests

Count of successful requests that Application Gateway has served. The request count can be further filtered to show count per each/specific backend pool-http setting combination.
Web Application Firewall matched rules
Web Application Firewall triggered rules

Backend metrics

For Application Gateway, the following metrics are available:

Healthy host count

The number of backends that are determined healthy by the health probe. You can filter on a per backend pool basis to show healthy/unhealthy hosts in a specific backend pool.
Unhealthy host count

The number of backends that are determined unhealthy by the health probe. You can filter on a per backend pool basis to show unhealthy hosts in a specific backend pool.

Metrics visualization

Browse to an application gateway, under Monitoring select Metrics. To view the available values, select the METRIC drop-down list.

In the following image, you see an example with three metrics displayed for the last 30 minutes:

To see a current list of metrics, see Supported metrics with Azure Monitor.

Alert rules on metrics

You can start alert rules based on metrics for a resource. For example, an alert can call a webhook or email an administrator if the throughput of the application gateway is above, below, or at a threshold for a specified period.

The following example walks you through creating an alert rule that sends an email to an administrator after throughput breaches a threshold:

select Add metric alert to open the Add rule page. You can also reach this page from the metrics page.
On the Add rule page, fill out the name, condition, and notify sections, and select OK.
- In the Condition selector, select one of the four values: Greater than, Greater than or equal, Less than, or Less than or equal to.
- In the Period selector, select a period from five minutes to six hours.
- If you select Email owners, contributors, and readers, the email can be dynamic based on the users who have access to that resource. Otherwise, you can provide a comma-separated list of users in the Additional administrator email(s) box.