Brotli compression in Azure Front Door not working without caching

3
votes

I have a backend pool in Azure Front Door which contains a number of VMs with IIS 10. Brotli compression extension is installed on all IIS. When I hit a VM directly, I can verify Brotli compression is working.

Two Routing Rules is enabled, both pointing to the same backend pool in Front Door.

  1. Rule one is with caching enabled. This one gets Brotli headers and compression from my IIS pool.
  2. Rule two is without caching enabled. Brotli headers are not shown in response, and the response is not compressed.

Why is compression only working when caching is enabled? I do not wish to cache Rule 2, only compress the response.

Rule 1 - Brotli working

enter image description here

Rule 2 - Brotli not working

enter image description here

1
azurecloudazure-front-door
In the rule 2 screenshot, the dynamic compression setting is missing. Are you sure you have this set to enabled? – Kashyap
@Kashyap dynamic compression can only be set if Caching is enabled – Morten OC
I think that's the answer. The brotli conversion is handled by dynamic compression. – Kashyap
@Kashyap thanks for your answer! So this is a limitation in Azure Front Door? As I do not want to cache my response, only compress it, but this option is not available without caching. – Morten OC
I'm seeing similar behavior. We have GZIP compression when accessing static resources directly against backend hosts, but if we go through AFD, no compression is taking place to the client. This is problematic given the size of our JS resources that are normally compressed. – RMD

1 Answers

0
votes

[Update] This is currently a limitation in AFD, confirmed by Microsoft.

Please vote on feature here https://feedback.azure.com/forums/217313-networking/suggestions/40186792-expand-azure-front-door-compression-support