To ensure that service levels are consistent with the business requirements, Instana conventionally uses SLO as defined by Google here: Service Level Objectives (SLO).
We have introduced Apdex (Application Performance Index) for Application and Website (open beta in version 250).
This feature will give more options to our customers to measure performance of their applications.
Some companies using Apdex https://www.apdex.org/index.php/apdex-vendors/
What is Apdex?
“Apdex is an open standard developed by an alliance of companies for measuring performance of software applications in computing”.
How Does Apdex Work?
The concept is quite simple, you define a satisfaction threshold: T, and users are classified according to the threshold:
Satisfied:
Users with high application responsiveness.
Users who experience response times are less or equal than the threshold (T) are considered to be Satisfied.
Tolerated:
A user with noticeable slow response from the application.
Users who experience response times are greater than T and less or equal 4 times T.
Frustrated:
Users with unacceptable performance, errors, this could lead to user abandon the application.
Users who experience response are times 4 times greater than T
How apdex is calculated?
The Apdex method converts various metrics into a single number on a uniform scale of 0 to 1 (0 being frustrated, 1 being satisfied). The resulting Apdex value is a numerical measure of user satisfaction with the performance of the enterprise application.
Apdex value (Apdex score) is a numerical measure of user satisfaction with the performance of the enterprise application.
Apdex will represent various metrics into a single number on a uniform scale of between 0 and 1 (0 being frustrated, 1 being satisfied)
Example of an Apdex score
In this example, we will use a website or application that receives 500 requests in 10 minutes where our Apdex threshold or T is set to 0.5 seconds (500ms).
- Let’s say that 310 requests were handled within 500ms, which qualifies as “Satisfactory” range.
- Then, 90 requests were handled between 500ms and 2000 ms, which would be in the “Tolerable” range.
- Lastly, the 100 remaining requests were either not handled properly (errors) or took longer than 2 seconds, so they would fall in the “Frustrated” range.
Thus giving us an Apdex score of 0.71 
Apdex Configuration
Can be setup for Website and Application.
To create an Apdex configuration or clone an existing Apdex configuration, go to the Apdex Management dialog, which you can reach by either clicking Add widget or by editing an existing widget. Then, click Manage Apdex.
Next, follow the steps to either create a configuration from scratch or by cloning an existing configuration.
( Full instruction in the doc : Adding Apdex widgets )
Example
Dashboard with 2 Apdex widgets for Website and Application.
The Dashboard above shows a poor end users experience (page load). This will lead to many questions:
- What Is a Good Apdex Score?
- is it a realistic threshold?
- is the correct response threshold that you want for this service/app?
- threshold is it too low? Can we readjust threshold?
- is it a poor app perf / network at end users is the issue?
Answer to questions above not only help define correct threshold, but also to troubleshoot poor performance.
What Is a Good Apdex Score?
Why Monitoring Apdex Score is NOT Enough?
In comment!!!