[bug#43494,v2,4/4] services: guix: Add guix-build-coordinator-queue-builds-service-type.

diff --git a/doc/guix.texi b/doc/guix.texi
index b2dde30ddb..767c99c5cb 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -27603,6 +27603,44 @@  input store items aren't already available.
 @end table
 @end deftp
 
+@defvar {Scheme Variable} guix-build-coordinator-queue-builds-service-type
+Service type for the
+guix-build-coordinator-queue-builds-from-guix-data-service script.  Its
+value must be a @code{guix-build-coordinator-queue-builds-configuration}
+object.
+@end defvar
+
+@deftp {Data Type} guix-build-coordinator-queue-builds-configuration
+Data type representing the options to the queue builds from guix data
+service script.
+
+@table @asis
+@item @code{package} (default: @code{guix-build-coordinator})
+The Guix Build Coordinator package to use.
+
+@item @code{user} (default: @code{"guix-build-coordinator-queue-builds"})
+The system user to run the service as.
+
+@item @code{coordinator} (default: @code{"http://localhost:8745"})
+The URI to use when connecting to the coordinator.
+
+@item @code{systems} (default: @code{#f})
+The systems for which to fetch derivations to build.
+
+@item @code{systems-and-targets} (default: @code{#f})
+An association list of system and target pairs for which to fetch
+derivations to build.
+
+@item @code{guix-data-service} (default: @code{"https://data.guix.gnu.org"})
+The Guix Data Service instance from which to query to find out about
+derivations to build.
+
+@item @code{processed-commits-file} (default: @code{"/var/cache/guix-build-coordinator-queue-builds/processed-commits"})
+A file to record which commits have been processed, to avoid needlessly
+processing them again if the service is restarted.
+
+@end table
+@end deftp
 
 @subsubheading Guix Data Service
 The @uref{http://data.guix.gnu.org,Guix Data Service} processes, stores
diff --git a/gnu/services/guix.scm b/gnu/services/guix.scm
index e4f5cf57b9..1493a24be5 100644
--- a/gnu/services/guix.scm
+++ b/gnu/services/guix.scm
@@ -65,6 +65,18 @@ 
 
             guix-build-coordinator-agent-service-type
 
+            guix-build-coordinator-queue-builds-configuration
+            guix-build-coordinator-queue-builds-configuration?
+            guix-build-coordinator-queue-builds-configuration-package
+            guix-build-coordinator-queue-builds-configuration-user
+            guix-build-coordinator-queue-builds-coordinator
+            guix-build-coordinator-queue-builds-configuration-systems
+            guix-build-coordinator-queue-builds-configuration-system-and-targets
+            guix-build-coordinator-queue-builds-configuration-guix-data-service
+            guix-build-coordinator-queue-builds-configuration-processed-commits-file
+
+            guix-build-coordinator-queue-builds-service-type
+
             <guix-data-service-configuration>
             guix-data-service-configuration
             guix-data-service-configuration?
@@ -137,6 +149,28 @@ 
    guix-build-coordinator-agent-configuration-non-derivation-substitute-urls
    (default #f)))
 
+(define-record-type* <guix-build-coordinator-queue-builds-configuration>
+  guix-build-coordinator-queue-builds-configuration
+  make-guix-build-coordinator-queue-builds-configuration
+  guix-build-coordinator-queue-builds-configuration?
+  (package              guix-build-coordinator-queue-builds-configuration-package
+                        (default guix-build-coordinator))
+  (user                 guix-build-coordinator-queue-builds-configuration-user
+                        (default "guix-build-coordinator-queue-builds"))
+  (coordinator          guix-build-coordinator-queue-builds-coordinator
+                        (default "http://localhost:8745"))
+  (systems              guix-build-coordinator-queue-builds-configuration-systems
+                        (default #f))
+  (systems-and-targets
+   guix-build-coordinator-queue-builds-configuration-system-and-targets
+   (default #f))
+  (guix-data-service
+   guix-build-coordinator-queue-builds-configuration-guix-data-service
+   (default "https://data.guix.gnu.org"))
+  (processed-commits-file
+   guix-build-coordinator-queue-builds-configuration-processed-commits-file
+   (default "/var/cache/guix-build-coordinator-queue-builds/processed-commits")))
+
 (define* (make-guix-build-coordinator-start-script database-uri-string
                                                    allocation-strategy
                                                    pid-file
@@ -360,6 +394,80 @@ 
    (description
     "Run a Guix Build Coordinator agent.")))
 
+(define (guix-build-coordinator-queue-builds-shepherd-services config)
+  (match-record config <guix-build-coordinator-queue-builds-configuration>
+    (package user coordinator systems systems-and-targets
+             guix-data-service processed-commits-file)
+    (list
+     (shepherd-service
+      (documentation "Guix Build Coordinator queue builds from Guix Data Service")
+      (provision '(guix-build-coordinator-queue-builds))
+      (requirement '(networking))
+      (start
+       #~(make-forkexec-constructor
+          (list
+           #$(file-append
+              package
+              "/bin/guix-build-coordinator-queue-builds-from-guix-data-service")
+           #$(string-append "--coordinator=" coordinator)
+           #$@(map (lambda (system)
+                     (string-append "--system=" system))
+                   (or systems '()))
+           #$@(map (match-lambda
+                     ((system . target)
+                      (string-append "--system-and-target=" system "=" target)))
+                   (or systems-and-targets '()))
+           #$@(if guix-data-service
+                  #~(#$(string-append "--guix-data-service=" guix-data-service))
+                  #~())
+           #$@(if processed-commits-file
+                  #~(#$(string-append "--processed-commits-file="
+                                      processed-commits-file))
+                  #~()))
+          #:user #$user
+          #:pid-file "/var/run/guix-build-coordinator-queue-builds/pid"
+          #:environment-variables
+          `(,(string-append
+              "GUIX_LOCPATH=" #$glibc-utf8-locales "/lib/locale")
+            "LC_ALL=en_US.utf8")
+          #:log-file "/var/log/guix-build-coordinator/queue-builds.log"))
+      (stop #~(make-kill-destructor))))))
+
+(define (guix-build-coordinator-queue-builds-activation config)
+  #~(begin
+      (use-modules (guix build utils))
+
+      (mkdir-p "/var/log/guix-build-coordinator")
+
+      ;; Allow writing the PID file
+      (mkdir-p "/var/run/guix-build-coordinator-queue-builds")
+      (chown "/var/run/guix-build-coordinator-queue-builds"
+             (passwd:uid %user)
+             (passwd:gid %user))))
+
+(define (guix-build-coordinator-queue-builds-account config)
+  (list (user-account
+         (name (guix-build-coordinator-queue-builds-configuration-user config))
+         (group "nogroup")
+         (system? #t)
+         (comment "Guix Build Coordinator queue-builds user")
+         (home-directory "/var/empty")
+         (shell (file-append shadow "/sbin/nologin")))))
+
+(define guix-build-coordinator-queue-builds-service-type
+  (service-type
+   (name 'guix-build-coordinator-queue-builds)
+   (extensions
+    (list
+     (service-extension shepherd-root-service-type
+                        guix-build-coordinator-queue-builds-shepherd-services)
+     (service-extension activation-service-type
+                        guix-build-coordinator-queue-builds-activation)
+     (service-extension account-service-type
+                        guix-build-coordinator-queue-builds-account)))
+   (description
+    "Run the Guix Build Coordinator queue builds script.")))
+
 
 ;;;
 ;;; Guix Data Service