I was trying to hook up my content with GraphCDN so I can cache the query result, and while doing that I noticed it gives me an error saying Error 503 illegal Vary header from backend.
In fact, this isn’t a bug from GraphCDN; it’s an error message shown from the Fastly (the underlying CDN provider of GraphCDN) which disallows malformed Vary headers as they stated in their documentation.
So I curled up the Content Delivery API and I noticed there’s no spaces on the Vary header.
< vary: Accept,Accept-Encoding
It should have a space after the comma, as stated by RFC 7231.
Hi @basix, where did you exactly read that a space is required after the comma? I can’t find it in RFC, and I’ve seen myself many times this compact form. Are you sure that that’s the reason why Fastly’s saying that the header is malformed, or maybe it could be something else?
I’m pretty sure Fastly is putting 502 because of Vary header since the error says this:
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
<title>503 Illegal Vary header from backend</title>
</head>
<body>
<h1>Error 503 Illegal Vary header from backend</h1>
<p>Illegal Vary header from backend</p>
<h3>Guru Mediation:</h3>
<p>Details: cache-icn1450034-ICN 1644386787 3055346844</p>
<hr>
<p>Varnish cache server</p>
</body>
</html>
However I couldn’t find any statement that the comma-separated list should have spaces except the example section of the RFC itself which is quite confusing…
I’ll deploy a simple endpoint with the Vary header like above and check if the error persists.
