Add docs for request profiling

Closes #23239

3 files changed, 16 insertions, 0 deletions

diff --git a/doc/administration/monitoring/performance/img/request_profile_result.png b/doc/administration/monitoring/performance/img/request_profile_result.png
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diff --git a/doc/administration/monitoring/performance/img/request_profiling_token.png b/doc/administration/monitoring/performance/img/request_profiling_token.png
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diff --git a/doc/administration/monitoring/performance/request_profiling.md b/doc/administration/monitoring/performance/request_profiling.md
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+# Request Profiling
+
+## Procedure
+1. Grab the profiling token from `Monitoring > Requests Profiles` admin page
+(highlighted in a blue in the image below).
+![Profile token](img/request_profiling_token.png)
+1. Pass the header `X-Profile-Token: <token>` to the request you want to profile. You can use any of these tools
+    * [ModHeader](https://chrome.google.com/webstore/detail/modheader/idgpnmonknjnojddfkpgkljpfnnfcklj) Chrome extension
+    * [Modify Headers](https://addons.mozilla.org/en-US/firefox/addon/modify-headers/) Firefox extension
+    * `curl --header 'X-Profile-Token: <token>' https://gitlab.example.com/group/project`
+1. Once request is finished (which will take a little longer than usual), you can
+view the profiling output from `Monitoring > Requests Profiles` admin page.
+![Profiling output](img/request_profile_result.png)
+
+## Cleaning up
+Profiling output will be cleared out every day via a Sidekiq worker.