time.to_first_byte

RTIME, read-only.

Available indeliverlog

The time interval since the request started up to the point before the vcl_deliver subroutine ran. When used in a string context, an RTIME variable like this one will be formatted as a number in seconds with 3 decimal digits of precision. In vcl_deliver this interval will be very close to time.elapsed. In vcl_log, the difference between time.elapsed and time.to_first_byte will be the time that it took to send the response body.

Try it out

time.to_first_byte is used in the following solution recipes. Recipes apply VCL to real-world use cases and can be deployed as-is, or adapted for your own service. See the full list of recipes for more inspiration.

Click RUN on a sample below to provision a Fastly service, execute the code on Fastly, and see how the function behaves.

Comprehensive logging

Fastly offers a myriad of different variables that you can log. See and test a large collection here.