envoyproxy/envoy

question: is the original authority available with a host rewrite?

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#13,834 opened on Oct 30, 2020

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area/access_logarea/httphelp wanted

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Description

I'm trying to add the original destination (authority) of a request via an access log, or even an additional request header before it gets rewritten for the upstream cluster request. Is this information available somewhere?

An access log with... still logs the rewritten host.

action.Route.HostRewriteSpecifier = &envoyroute.RouteAction_HostRewrite{
	HostRewrite: "my-new-upstream-host,
}

"req_host":     "%REQ(:AUTHORITY)%"

We can use %REQ(X-ENVOY-ORIGINAL-PATH?:PATH)% for the original path. Is there something like that for the original authority?

Contributor guide

Research direction
Investigate whether there is a built in variable like '%ORIGINAL AUTHORITY%' or a header like 'X Envoy Original Host'. Check Envoy's access log format documentation and the http connection manager configuration. If not available, consider if a custom filter or Lua script can preserve the original authority.
Tech stack
cpp
Domain
backend
Issue type
Documentation
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
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Active
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Clear
Prerequisites
Git
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70