X-Request-Start header

[scalp42]

Hi folks,

Looking at the headers documentation (https://fabiolb.net/feature/http-headers/), we can't figure out if Fabio supports setting a dynamic header based on micro/milliseconds since epoch.

Example with Nginx:

proxy_set_header X-Request-Start "t=${msec}";

or Apache:

RequestHeader set X-Request-Start "%t"

By setting the header, it allows visibility into request queuing to the app from farther upstream (Fabio in our scenario).

It's also needed for APM vendors (New Relic, Scout, Instana, etc):

• https://docs.newrelic.com/docs/apm/applications-menu/features/request-queue-server-configuration-examples
• https://docs.scoutapm.com/#http-header

Let us know if it's possible.

Thanks in advance ✌️

[aaronhurt]

@scalp42 There isn't any current dynamic header support other than the specific documented cases. There is an open issue though with ongoing discussion: #168

Going to close this as a duplicate of #168 as jippi actually mentions this exact case in that issue.

Feel free to re-open if the solutions discussed there wouldn't resolve your issue.