daemon: Run 'guix substitute --substitute' as an agent.

This avoids spawning one substitute process per substitution.

* nix/libstore/build.cc (class Worker)[substituter]: New field.
[outPipe, logPipe, pid]: Remove.
(class SubstitutionGoal)[expectedHashStr, status, substituter]: New fields.
(SubstitutionGoal::timedOut): Adjust to check 'substituter'.
(SubstitutionGoal::tryToRun): Remove references to 'outPipe' and
'logPipe'.  Run "guix substitute --substitute" as an 'Agent'.  Send the
request with 'writeLine'.
(SubstitutionGoal::finished): Likewise.
(SubstitutionGoal::handleChildOutput): Change to fill in
'expectedHashStr' and 'status'.
(SubstitutionGoal::handleEOF): Call 'wakeUp' unconditionally.
(SubstitutionGoal::~SubstitutionGoal): Adjust to check 'substituter'.
* guix/scripts/substitute.scm (process-substitution): Write "success\n"
to stdout upon success.
(%error-to-file-descriptor-4?): New variable.
(guix-substitute): Set 'current-error-port' to file descriptor 4
unless (%error-to-file-descriptor-4?) is false.
Remove "--substitute" arguments.  Loop reading line from stdin.
* tests/substitute.scm <top level>: Call '%error-to-file-descriptor-4?'.
(request-substitution): New procedure.
("substitute, no signature")
("substitute, invalid hash")
("substitute, unauthorized key")
("substitute, authorized key")
("substitute, unauthorized narinfo comes first")
("substitute, unsigned narinfo comes first")
("substitute, first narinfo is unsigned and has wrong hash")
("substitute, first narinfo is unsigned and has wrong refs")
("substitute, two invalid narinfos")
("substitute, narinfo with several URLs"): Adjust to new "guix
substitute --substitute" calling convention.

1 files changed, 25 insertions, 9 deletions

diff --git a/guix/scripts/substitute.scm b/guix/scripts/substitute.scm
index 5e392eaa8b..73abd3f029 100755
--- a/guix/scripts/substitute.scm
+++ b/guix/scripts/substitute.scm
@@ -88,6 +88,7 @@
             write-narinfo
 
             %allow-unauthenticated-substitutes?
+            %error-to-file-descriptor-4?
 
             substitute-urls
             guix-substitute))
@@ -1016,7 +1017,10 @@ DESTINATION as a nar file.  Verify the substitute against ACL."
 
       ;; Skip a line after what 'progress-reporter/file' printed, and another
       ;; one to visually separate substitutions.
-      (display "\n\n" (current-error-port)))))
+      (display "\n\n" (current-error-port))
+
+      ;; Tell the daemon that we're done.
+      (display "success\n" (current-output-port)))))
 
 
 ;;;
@@ -1127,6 +1131,11 @@ default value."
   (unless (string->uri uri)
     (leave (G_ "~a: invalid URI~%") uri)))
 
+(define %error-to-file-descriptor-4?
+  ;; Whether to direct 'current-error-port' to file descriptor 4 like
+  ;; 'guix-daemon' expects.
+  (make-parameter #t))
+
 (define-command (guix-substitute . args)
   (category internal)
   (synopsis "implement the build daemon's substituter protocol")
@@ -1140,9 +1149,9 @@ default value."
 
   ;; The daemon's agent code opens file descriptor 4 for us and this is where
   ;; stderr should go.
-  (parameterize ((current-error-port (match args
-                                       (("--query") (fdopen 4 "wl"))
-                                       (_ (current-error-port)))))
+  (parameterize ((current-error-port (if (%error-to-file-descriptor-4?)
+                                         (fdopen 4 "wl")
+                                         (current-error-port))))
     ;; Redirect diagnostics to file descriptor 4 as well.
     (guix-warning-port (current-error-port))
 
@@ -1184,15 +1193,22 @@ default value."
                                    #:cache-urls (substitute-urls)
                                    #:acl acl)
                     (loop (read-line)))))))
-         (("--substitute" store-path destination)
+         (("--substitute")
           ;; Download STORE-PATH and store it as a Nar in file DESTINATION.
           ;; Specify the number of columns of the terminal so the progress
           ;; report displays nicely.
           (parameterize ((current-terminal-columns (client-terminal-columns)))
-            (process-substitution store-path destination
-                                  #:cache-urls (substitute-urls)
-                                  #:acl (current-acl)
-                                  #:print-build-trace? print-build-trace?)))
+            (let loop ()
+              (match (read-line)
+                ((? eof-object?)
+                 #t)
+                ((= string-tokenize ("substitute" store-path destination))
+                 (process-substitution store-path destination
+                                       #:cache-urls (substitute-urls)
+                                       #:acl (current-acl)
+                                       #:print-build-trace?
+                                       print-build-trace?)
+                 (loop))))))
          ((or ("-V") ("--version"))
           (show-version-and-exit "guix substitute"))
          (("--help")