Dynatrace RUM using manual injection

[agrawal_shashan]

Hey Guys, I am trying to understand the agentless manual injection methods. I have been using JavaScript tag method for a while without any issues but I am just concerned that it loads the JS synchronously and let's say if the JS takes time to load then it blocks the actual page to load which is NOT GOOD.

https://www.dynatrace.com/support/help/shortlink/rum-injection#manual-insertion 

I can see there is another insertion method Code snippet deferred (asyncCS) which gets loaded asynchronously in the background and it doesn't affect the page load.

I want to understand if we use this, will there be any disadvantages?

1. If we change the monitoring settings in Dynatrace UI, do i have to update the snippet again on the pages?
2. Will there be any missing monitoring data? I mean if the JS does not get loaded fully on time and page starts loading before that, will we miss anything in terms of metrics?
3. Do we need to specifically mention "async" keyword while loading the script or this is built-in the JS and we just have to load it from the page?

Best Regards,
Shashank

[radek_jasinski · Accepted solution]

Hi Shashan,

In the case of asyncCS you must proceed almost exactly as with syncCS. Dynatrace recommend that you regularly update the snippet:

You can use DT Api to dynamically downloads the monitoring code into your application. The monitoring code is loaded asynchronously.

https://www.dynatrace.com/support/help/dynatrace-api/environment-api/rum/real-user-monitoring-javasc...

Radek