It's quite common for server-side web frameworks to send a single request through their stack multiple times / especially when there is any form of "middleware" concept involved.
Often there's a need to skip some
middleware on the second or third time through.
I've built systems in the past that do all sorts of re-dispatching.
One example: in development my API might live at /api/... but in production I might use api.my.site - with middleware that detects that host, rewrites the incoming request to add that /api/ prefix and then runs it though the stack again.
Authentication is a very common way this pattern is applied - check cookies / authorization headers / whatever, then add the authenticate user to the request somehow and re-dispatch the request through the stack so other layers can see who the user is.
Often there's a need to skip some middleware on the second or third time through.
I've built systems in the past that do all sorts of re-dispatching.
One example: in development my API might live at /api/... but in production I might use api.my.site - with middleware that detects that host, rewrites the incoming request to add that /api/ prefix and then runs it though the stack again.
Authentication is a very common way this pattern is applied - check cookies / authorization headers / whatever, then add the authenticate user to the request somehow and re-dispatch the request through the stack so other layers can see who the user is.