[bug#47174] [PATCH v3 2/2] substitute: Handle closing connections to substitute servers.

[Christopher Baines <mail@cbaines.net>]

When reusing a HTTP connection to fetch multiple nars, and the remote server
signals that the connection should be closed.

* guix/scripts/substitute.scm (process-substitution): Close connections to
substitute servers when a Connection: close header is specified in the
response.
---
 guix/scripts/substitute.scm | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/guix/scripts/substitute.scm b/guix/scripts/substitute.scm
index 96f425eaa0..208b8f1273 100755
--- a/guix/scripts/substitute.scm
+++ b/guix/scripts/substitute.scm
@@ -464,7 +464,9 @@ PORT."
     (case (uri-scheme uri)
       ((file)
        (let ((port (open-file (uri-path uri) "r0b")))
-         (values port (stat:size (stat port)))))
+         (values port
+                 (stat:size (stat port))
+                 (const #t))))          ; no cleanup to do
       ((http https)
        (guard (c ((http-get-error? c)
                   (leave (G_ "download from '~a' failed: ~a, ~s~%")
@@ -487,7 +489,12 @@ PORT."
                                        #:keep-alive? #t
                                        #:buffered? #f)))
                (values raw
-                       (response-content-length response)))))))
+                       (response-content-length response)
+                       (match (assq 'connection (response-headers response))
+                         (('connection 'close)
+                          (lambda ()
+                            (close-port port)))
+                         (_ (const #t)))))))))
       (else
        (leave (G_ "unsupported substitute URI scheme: ~a~%")
               (uri->string uri)))))
@@ -504,7 +511,7 @@ PORT."
       (format (current-error-port)
               (G_ "Downloading ~a...~%") (uri->string uri)))
 
-    (let*-values (((raw download-size)
+    (let*-values (((raw download-size post-fetch-cleanup)
                    ;; 'guix publish' without '--cache' doesn't specify a
                    ;; Content-Length, so DOWNLOAD-SIZE is #f in this case.
                    (fetch uri))
@@ -565,6 +572,10 @@ PORT."
       ;; Wait for the reporter to finish.
       (every (compose zero? cdr waitpid) pids)
 
+      ;; Do post-fetch cleanup, maybe closing the HTTP connection if HTTP is
+      ;; being used, and the connection should be closed
+      (post-fetch-cleanup)
+
       ;; Skip a line after what 'progress-reporter/file' printed, and another
       ;; one to visually separate substitutions.  When PRINT-BUILD-TRACE? is
       ;; true, leave it up to (guix status) to prettify things.
-- 
2.31.1