From 6d459a442d73628a0628385283c7cf04dff1b797 Mon Sep 17 00:00:00 2001
From: Tobias Geerinckx-Rice <address@hidden>
Date: Tue, 21 Mar 2017 15:31:56 +0100
Subject: [PATCH] http-client: Warn on proxy cache misses.

Still not a good idea.

* guix/http-client.scm (http-fetch): Add #:peek-behind-proxy parameter
to expose caching proxy implementation details as a scary warning.
* guix/scripts/substitute.scm (fetch): Use it.
---
 guix/http-client.scm        | 10 +++++++++-
 guix/scripts/substitute.scm |  3 ++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/guix/http-client.scm b/guix/http-client.scm
index 6874c51..2366f5e 100644
--- a/guix/http-client.scm
+++ b/guix/http-client.scm
@@ -2,6 +2,7 @@
 ;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <address@hidden>
 ;;; Copyright © 2015 Mark H Weaver <address@hidden>
 ;;; Copyright © 2012, 2015 Free Software Foundation, Inc.
+;;; Copyright © 2017 Tobias Geerinckx-Rice <address@hidden>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -222,7 +223,8 @@ or if EOF is reached."
 
 (define* (http-fetch uri #:key port (text? #f) (buffered? #t)
                      keep-alive? (verify-certificate? #t)
-                     (headers '((user-agent . "GNU Guile"))))
+                     (headers '((user-agent . "GNU Guile")))
+                     (peek-behind-cache? #f))
   "Return an input port containing the data at URI, and the expected number of
 bytes available or #f.  If TEXT? is true, the data at URI is considered to be
 textual.  Follow any HTTP redirection.  When BUFFERED? is #f, return an
@@ -253,8 +255,14 @@ Raise an '&http-get-error' condition if downloading fails."
                      (http-get uri #:streaming? #t #:port port
                                #:keep-alive? #t
                                #:headers headers))
+                    ((headers)
+                     (response-headers resp))
                     ((code)
                      (response-code resp)))
+        (when (and peek-behind-cache?
+                   (equal? (assoc-ref headers 'x-cache-status) "MISS"))
+              (warning (_ "the caching proxy is working properly!~%"))
+              (warning (_ "and there's nothing you can do about it.~%")))
         (case code
           ((200)
            (values data (response-content-length resp)))
diff --git a/guix/scripts/substitute.scm b/guix/scripts/substitute.scm
index faeb019..4a4f115 100755
--- a/guix/scripts/substitute.scm
+++ b/guix/scripts/substitute.scm
@@ -216,7 +216,8 @@ provide."
                (unless (or buffered? (not (file-port? port)))
                  (setvbuf port _IONBF)))
              (http-fetch uri #:text? #f #:port port
-                         #:verify-certificate? #f))))))
+                         #:verify-certificate? #f
+                         #:peek-behind-cache? #t))))))
     (else
      (leave (_ "unsupported substitute URI scheme: ~a~%")
             (uri->string uri)))))
-- 
2.9.3