Introduction

InspectIT The inspectIT now comes with a new, experimental feature: Browser End User Experience Monitoring (EUM). This feature allows you to measure the performance at the browser of the End User, giving more detailed insights than back-end instrumentation alone.

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Currently, the captured metrics are only stored in the influx time-series database connected to the CMR and can be viewed using Grafana Dashboards.
As a future feature however, it is planned to also integrate the captured End User Traces into the inspectIT UIs tracing view.

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Prerequisites

The current implementation of the End User Monitoring only operates on the Java Servlet API, therefore only applications based on this API are supported.
The used Servlet Container should not matter, as long as it adheres to the Servlet API standard. Therefore any common Servlet Container (e.g. Apache Tomcat, Glassfish) can be used.However, as

All you need to do is to configure your application to start with the normal inspectIT Java Agent, the EUM-Instrumentation happens fully automatically when configured as described below.

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To enable EUM, you first have to tick the corresponding Activate checkbox.

In addition, you have to specify the "Script Base URL": here you should provide a URL prefix, under which the Java Agent will make the JavaScript Agent Script available and to which the JavaScript Agent will send back the results.
As this injection works through the Java Servlet API, you have to choose a URL prefix which is mapped to at least one Filter or Servlet.
A typical good choice here is the URL under which your static content is available, e.g. "/scripts/" or "/img/".

Finally, you can select from the table which modules of the JavaScript Agent you would like to use, a description of each is given below:

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If the EUM does not work even though you configured it as described above, you should look here first as we present the most common problems with their solutions in this section.
However, first make sure you have restarted your instrumented Servlet Container, as currently changes to the environment settings are only effective after a restart. 

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These tags should be the first tags to appear within the head section (or body if you don't have a head section).

Troubleshooting:

• If these tags are not present, first double check that EUM is enabled for your JVM which delivers the responses to the End User.
• A second possible root cause might be compression: The Java Agent has to parse the HTML delivered by your application in order to inject the JavaScript Agent tags.
• If the HTML is passed already compressed to the Servlet API output stream, the Agent is not able to do this, therefore try disabling the compression of the responses.
• If the compression is done "on-the-fly" however, e.g. by using a Servlet API Filter to perform the compression, compression should not affect the EUM injection.

Problem: JavaScript Agent script not reachable

This issue can be detected by opening your webpage with your browsers developer console opened up:
The tags shown above are correctly injected, however the browser is unable to fetch the JavaScript Agent source?

The most common reason for this problem is that the configured "Script Base Url" is not a valid prefix, meaning that it is not mapped to any of your filters or servlets.
You can test this by manually trying to fetch the JavaScript Agent source: . For example, if your server is hosted on "localhost:8080" and you configured the base-url as "/scripts/", try entering "localhost:8080/img/inspectit_jsagent_1_1.js" in your browser.
If everything works, you should receive the source of the agent, otherwise a HTTP 404 error.

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