Get an overview of how the Apdex score is calculated and Configure Apdex Settings.

The Application Performance Index (Apdex) is an industry standard that can help you understand how the response time of a service compares to a predefined response time threshold.

Overview

You can measure the performance of a service using Request, Error, and Duration (RED) metrics for a given time frame. But it is hard to compare these values and understand how each service performs. Apdex helps you compare the response time of a service based on the response time threshold that you define.

When you send your applications trace data to Wavefront, the application data is detected as first-class citizens using the traces, and the Apdex score is calculated using the threshold value (T) you define. Use apdex() to query the Apdex score of a service, view the results in charts, and create alerts.

The default threshold value (T) is set to 100ms, and only Super Admin users can configure the threshold (T).

Apdex score

The Apdex score is calculated using the following equation:

shows the equation used to calculate the Apdex score. Apdex score = (Satisfied count + (Tolerating count/2)/Total samples

The table below defines the terms used in the equation.

Term Description
ApdexT The Apdex score is calculated based on the response time threshold (T). Only super admin users can change this value. See Configure the Threshold (T) Value.
Satisfied count Number of requests that received a response in T or less.
Tolerating count Number of requests that are 4 times T (4T) or less.
Frustrated count Number of requests that take more than 4 times T (4T) to complete. These requests are not used to calculate the Apdex score.
Total samples Total number of requests used to calculate your Apdex score.

Interpreting the Apdex Score

The Apdex score is a value between 0 to 1.

  • If the score is 0, none of the requests of the service satisfied the response time threshold (T) you defined.
  • If the score is 1, all the requests of the service satisfy T.

Wavefront uses the following Apdex score range to help you understand how your service is performing:

Range Service Performance Color
0.94 - 1 Excellent blue for Excellent
0.85 - 0.93 Good blue for Excellent
0.70 - 0.84 Fair blue for Excellent
0.50 - 0.69 Poor blue for Excellent
0.49 - 0 Unacceptable blue for Excellent

Example

Let’s take a look at an example to get familiar with how the Apdex score is calculated.

The shopping service in the beachshirts application handles 300 requests during a 3 minute period, and T is set to 500ms.

  • 230 requests were handled within 500ms. This is the satisfied count.
  • 40 requests were handled between 500ms and 2 seconds (2000ms). This is the tolerating count.
  • The remaining 30 requests ended up as errors or took longer than 4T (2 seconds) to complete. This is the frustrated count, and it is not used to calculate the Apdex score.

    ApdexT = ( 230 + (40/2)) / 300 = 0.83

Based on the Apdex score, you now know that the performance of the shopping service is good.

Configure the Threshold (T) Value

Super Admin users can change the response time threshold (T), which defaults to 100ms using one of the following options:

  • Using the Application Configuration page.
  • Using the legend on the application status page that has the application map, table view, or grid view.

Update the Application Configuration Page

Follow these steps:

  1. Click Applications > Application Configurations. You see a list of the applications that send trace data to Wavefront.
  2. Click on the application that has the services you want to configure. Now, you see a list of all the services in the application.
  3. Click the icon with the three vertical dots next to the service name and click Edit.

    The image shows where to click to edit the threshold value.

  4. Update the Threshold value and click Save. The image shows where to update the threshold value. It has a blue outline to highlight the threshold value.

Update the Legend on the Application Status Page

You can update the response time threshold (T) using the Settings icon on the app map, table view, or grid view on the Application Status page.

  1. Click Applications > Application Status.
  2. Click the settings icon on the app map, table view, or grid view.
  3. Under Legend Settings, select Apdex.
  4. Click Configure Apdex.

    The image the setting and the legend setting with Apdex selected from the drop down. The configure apdex section is highlighted with a blue box. You need to click it to update the threshold value.
    Now, you see a list of all the services that send trace data to Wavefront. You can sort the table by the service name, application name, service status (active or inactive), Apdex score, and the threshold (T) value.

  5. Click the icon with the three vertical dots next to the service name and click Edit. The image shows where to click to edit the threshold value.
  6. Update the Threshold value and click Save. The image shows where to update the threshold value. It has a blue outline to highlight the threshold value.

See Also

  • Learn how to use the apdex() function, to see Apdex score data on charts, and create alerts.
  • Use apdexLatency() to query the satisfied threshold (T) and toleration threshold (4T) of a service.