services: guix: Add guix-build-coordinator-service-type.

* gnu/services/guix.scm (<guix-build-coordinator-configuration>): New record
type.
(guix-build-coordinator-configuration, guix-build-coordinator-configuration?,
guix-build-coordinator-configuration-package,
guix-build-coordinator-configuration-user,
guix-build-coordinator-configuration-group,
guix-build-coordinator-configuration-datastore-uri-string,
guix-build-coordinator-configuration-agent-communication-uri-string,
guix-build-coordinator-configuration-client-communication-uri-string,
guix-build-coordinator-configuration-allocation-strategy,
guix-build-coordinator-configuration-hooks,
guix-build-coordinator-configuration-guile,
make-guix-build-coordinator-start-script,
guix-build-coordinator-shepherd-services, guix-build-coordinator-activation,
guix-build-coordinator-account): New procedures.
(guix-build-coordinator-service-type): New variable.
* gnu/tests/guix.scm (%test-guix-build-coordinator): New variable.
* doc/guix.texi (Guix Services): Document it.

doc/guix.texi

@@ -27764,6 +27764,73 @@ The complete list of possible options can be found in the man page for
 @node Guix Services
 @subsection Guix Services
 
+@subsubheading Guix Build Coordinator
+The @uref{https://git.cbaines.net/guix/build-coordinator/,Guix Build
+Coordinator} aids in distributing derivation builds among machines
+running an @dfn{agent}.  The build daemon is still used to build the
+derivations, but the Guix Build Coordinator manages allocating builds
+and working with the results.
+
+@quotation Note
+This service is considered experimental.  Configuration options may be
+changed in a backwards-incompatible manner, and not all features have
+been thorougly tested.
+@end quotation
+
+The Guix Build Coordinator consists of one @dfn{coordinator}, and one or
+more connected @dfn{agent} processes. The coordinator process handles
+clients submitting builds, and allocating builds to agents. The agent
+processes talk to a build daemon to actually perform the builds, then
+send the results back to the coordinator.
+
+There is a script to run the coordinator component of the Guix Build
+Coordinator, but the Guix service uses a custom Guile script instead, to
+provide better integration with G-expressions used in the configuration.
+
+@defvar {Scheme Variable} guix-build-coordinator-service-type
+Service type for the Guix Build Coordinator.  Its value must be a
+@code{guix-build-coordinator-configuration} object.
+@end defvar
+
+@deftp {Data Type} guix-build-coordinator-configuration
+Data type representing the configuration of the Guix Build Coordinator.
+
+@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"})
+The system user to run the service as.
+
+@item @code{group} (default: @code{"guix-build-coordinator"})
+The system group to run the service as.
+
+@item @code{database-uri-string} (default: @code{"sqlite:///var/lib/guix-build-coordinator/guix_build_coordinator.db"})
+The URI to use for the database.
+
+@item @code{agent-communication-uri} (default: @code{"http://0.0.0.0:8745"})
+The URI describing how to listen to requests from agent processes.
+
+@item @code{client-communication-uri} (default: @code{"http://127.0.0.1:8746"})
+The URI describing how to listen to requests from clients.  The client
+API allows submitting builds and currently isn't authenticated, so take
+care when configuring this value.
+
+@item @code{allocation-strategy} (default: @code{#~basic-build-allocation-strategy})
+A G-expression for the allocation strategy to be used.  This is a
+procedure that takes the datastore as an argument and populates the
+allocation plan in the database.
+
+@item @code{hooks} (default: @var{'()})
+An association list of hooks.  These provide a way to execute arbitrary
+code upon certian events, like a build result being processed.
+
+@item @code{guile} (default: @code{guile-3.0-latest})
+The Guile package with which to run the Guix Build Coordinator.
+
+@end table
+@end deftp
+
 @subsubheading Guix Data Service
 The @uref{http://data.guix.gnu.org,Guix Data Service} processes, stores
 and provides data about GNU Guix.  This includes information about

gnu/services/guix.scm

@@ -17,20 +17,40 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (gnu services guix)
+  #:use-module (srfi srfi-1)
   #:use-module (ice-9 match)
   #:use-module (guix gexp)
   #:use-module (guix records)
+  #:use-module (guix packages)
   #:use-module ((gnu packages base)
                 #:select (glibc-utf8-locales))
   #:use-module (gnu packages admin)
+  #:use-module (gnu packages databases)
   #:use-module (gnu packages web)
+  #:use-module (gnu packages guile)
+  #:use-module (gnu packages guile-xyz)
+  #:use-module (gnu packages package-management)
   #:use-module (gnu services)
   #:use-module (gnu services base)
   #:use-module (gnu services admin)
   #:use-module (gnu services shepherd)
   #:use-module (gnu services getmail)
   #:use-module (gnu system shadow)
-  #:export (<guix-data-service-configuration>
+  #:export (guix-build-coordinator-configuration
+            guix-build-coordinator-configuration?
+            guix-build-coordinator-configuration-package
+            guix-build-coordinator-configuration-user
+            guix-build-coordinator-configuration-group
+            guix-build-coordinator-configuration-datastore-uri-string
+            guix-build-coordinator-configuration-agent-communication-uri-string
+            guix-build-coordinator-configuration-client-communication-uri-string
+            guix-build-coordinator-configuration-allocation-strategy
+            guix-build-coordinator-configuration-hooks
+            guix-build-coordinator-configuration-guile
+
+            guix-build-coordinator-service-type
+
+            <guix-data-service-configuration>
             guix-data-service-configuration
             guix-data-service-configuration?
             guix-data-service-package
@@ -45,11 +65,185 @@
 
 ;;;; Commentary:
 ;;;
-;;; This module implements a service that to run instances of the Guix Data
+;;; Services specifically related to GNU Guix.
-;;; Service, which provides data about Guix over time.
 ;;;
 ;;;; Code:
 
+(define-record-type* <guix-build-coordinator-configuration>
+  guix-build-coordinator-configuration make-guix-build-coordinator-configuration
+  guix-build-coordinator-configuration?
+  (package                         guix-build-coordinator-configuration-package
+                                   (default guix-build-coordinator))
+  (user                            guix-build-coordinator-configuration-user
+                                   (default "guix-build-coordinator"))
+  (group                           guix-build-coordinator-configuration-group
+                                   (default "guix-build-coordinator"))
+  (database-uri-string
+   guix-build-coordinator-configuration-datastore-uri-string
+   (default "sqlite:///var/lib/guix-build-coordinator/guix_build_coordinator.db"))
+  (agent-communication-uri-string
+   guix-build-coordinator-configuration-agent-communication-uri-string
+   (default "http://0.0.0.0:8745"))
+  (client-communication-uri-string
+   guix-build-coordinator-configuration-client-communication-uri-string
+   (default "http://127.0.0.1:8746"))
+  (allocation-strategy
+   guix-build-coordinator-configuration-allocation-strategy
+   (default #~basic-build-allocation-strategy))
+  (hooks                           guix-build-coordinator-configuration-hooks
+                                   (default '()))
+  (guile                           guix-build-coordinator-configuration-guile
+                                   (default guile-3.0-latest)))
+
+(define* (make-guix-build-coordinator-start-script database-uri-string
+                                                   allocation-strategy
+                                                   pid-file
+                                                   guix-build-coordinator-package
+                                                   #:key
+                                                   agent-communication-uri-string
+                                                   client-communication-uri-string
+                                                   (hooks '())
+                                                   (guile guile-3.0))
+  (program-file
+   "start-guix-build-coordinator"
+   (with-extensions (cons guix-build-coordinator-package
+                          ;; This is a poorly constructed Guile load path,
+                          ;; since it contains things that aren't Guile
+                          ;; libraries, but it means that the Guile libraries
+                          ;; needed for the Guix Build Coordinator don't need
+                          ;; to be individually specified here.
+                          (map second (package-inputs
+                                       guix-build-coordinator-package)))
+     #~(begin
+         (use-modules (srfi srfi-1)
+                      (ice-9 match)
+                      (web uri)
+                      (prometheus)
+                      (guix-build-coordinator hooks)
+                      (guix-build-coordinator datastore)
+                      (guix-build-coordinator build-allocator)
+                      (guix-build-coordinator coordinator))
+
+         (let* ((metrics-registry (make-metrics-registry
+                                   #:namespace
+                                   "guixbuildcoordinator_"))
+                (datastore (database-uri->datastore
+                            #$database-uri-string
+                            #:metrics-registry metrics-registry))
+                (hooks
+                 (list #$@(map (match-lambda
+                                 ((name . hook-gexp)
+                                  #~(cons name #$hook-gexp)))
+                               hooks)))
+                (hooks-with-defaults
+                 `(,@hooks
+                   ,@(remove (match-lambda
+                               ((name . _) (assq-ref hooks name)))
+                             %default-hooks)))
+                (build-coordinator (make-build-coordinator
+                                    #:datastore datastore
+                                    #:hooks hooks-with-defaults
+                                    #:metrics-registry metrics-registry
+                                    #:allocation-strategy #$allocation-strategy)))
+
+           (run-coordinator-service
+            build-coordinator
+            #:update-datastore? #t
+            #:pid-file #$pid-file
+            #:agent-communication-uri (string->uri
+                                       #$agent-communication-uri-string)
+            #:client-communication-uri (string->uri
+                                        #$client-communication-uri-string)))))
+   #:guile guile))
+
+(define (guix-build-coordinator-shepherd-services config)
+  (match-record config <guix-build-coordinator-configuration>
+    (package user group database-uri-string
+             agent-communication-uri-string
+             client-communication-uri-string
+             allocation-strategy
+             hooks
+             guile)
+    (list
+     (shepherd-service
+      (documentation "Guix Build Coordinator")
+      (provision '(guix-build-coordinator))
+      (requirement '(networking))
+      (start #~(make-forkexec-constructor
+                (list #$(make-guix-build-coordinator-start-script
+                         database-uri-string
+                         allocation-strategy
+                         "/var/run/guix-build-coordinator/pid"
+                         package
+                         #:agent-communication-uri-string
+                         agent-communication-uri-string
+                         #:client-communication-uri-string
+                         client-communication-uri-string
+                         #:hooks hooks
+                         #:guile guile))
+                #:user #$user
+                #:group #$group
+                #:pid-file "/var/run/guix-build-coordinator/pid"
+                ;; Allow time for migrations to run
+                #:pid-file-timeout 60
+                #:environment-variables
+                `(,(string-append
+                    "GUIX_LOCPATH=" #$glibc-utf8-locales "/lib/locale")
+                  "LC_ALL=en_US.utf8")
+                #:log-file "/var/log/guix-build-coordinator/coordinator.log"))
+      (stop #~(make-kill-destructor))))))
+
+(define (guix-build-coordinator-activation config)
+  #~(begin
+      (use-modules (guix build utils))
+
+      (define %user (getpw "guix-build-coordinator"))
+
+      (chmod "/var/lib/guix-build-coordinator" #o755)
+
+      (mkdir-p "/var/log/guix-build-coordinator")
+
+      ;; Allow writing the PID file
+      (mkdir-p "/var/run/guix-build-coordinator")
+      (chown "/var/run/guix-build-coordinator"
+             (passwd:uid %user)
+             (passwd:gid %user))))
+
+(define (guix-build-coordinator-account config)
+  (match-record config <guix-build-coordinator-configuration>
+    (user group)
+    (list (user-group
+           (name group)
+           (system? #t))
+          (user-account
+           (name user)
+           (group group)
+           (system? #t)
+           (comment "Guix Build Coordinator user")
+           (home-directory "/var/lib/guix-build-coordinator")
+           (shell (file-append shadow "/sbin/nologin"))))))
+
+(define guix-build-coordinator-service-type
+  (service-type
+   (name 'guix-build-coordinator)
+   (extensions
+    (list
+     (service-extension shepherd-root-service-type
+                        guix-build-coordinator-shepherd-services)
+     (service-extension activation-service-type
+                        guix-build-coordinator-activation)
+     (service-extension account-service-type
+                        guix-build-coordinator-account)))
+   (default-value
+     (guix-build-coordinator-configuration))
+   (description
+    "Run an instance of the Guix Build Coordinator.")))
+
+
+;;;
+;;; Guix Data Service
+;;;
+
 (define-record-type* <guix-data-service-configuration>
   guix-data-service-configuration make-guix-data-service-configuration
   guix-data-service-configuration?

gnu/tests/guix.scm

@@ -35,7 +35,80 @@
   #:use-module (guix store)
   #:use-module (guix utils)
   #:use-module (ice-9 match)
-  #:export (%test-guix-data-service))
+  #:export (%test-guix-build-coordinator
+            %test-guix-data-service))
+
+;;;
+;;; Guix Build Coordinator
+;;;
+
+(define %guix-build-coordinator-os
+  (simple-operating-system
+   (service dhcp-client-service-type)
+   (service guix-build-coordinator-service-type)))
+
+(define (run-guix-build-coordinator-test)
+  (define os
+    (marionette-operating-system
+     %guix-build-coordinator-os
+     #:imported-modules '((gnu services herd)
+                          (guix combinators))))
+
+  (define forwarded-port 8745)
+
+  (define vm
+    (virtual-machine
+     (operating-system os)
+     (memory-size 1024)
+     (port-forwardings `((,forwarded-port . 8745)))))
+
+  (define test
+    (with-imported-modules '((gnu build marionette))
+      #~(begin
+          (use-modules (srfi srfi-11) (srfi srfi-64)
+                       (gnu build marionette)
+                       (web uri)
+                       (web client)
+                       (web response))
+
+          (define marionette
+            (make-marionette (list #$vm)))
+
+          (mkdir #$output)
+          (chdir #$output)
+
+          (test-begin "guix-build-coordinator")
+
+          (test-assert "service running"
+            (marionette-eval
+             '(begin
+                (use-modules (gnu services herd))
+                (match (start-service 'guix-build-coordinator)
+                  (#f #f)
+                  (('service response-parts ...)
+                   (match (assq-ref response-parts 'running)
+                     ((pid) (number? pid))))))
+             marionette))
+
+          (test-equal "http-get"
+            200
+            (let-values
+                (((response text)
+                  (http-get #$(simple-format
+                               #f "http://localhost:~A/metrics" forwarded-port)
+                            #:decode-body? #t)))
+              (response-code response)))
+
+          (test-end)
+          (exit (= (test-runner-fail-count (test-runner-current)) 0)))))
+
+  (gexp->derivation "guix-build-coordinator-test" test))
+
+(define %test-guix-build-coordinator
+  (system-test
+   (name "guix-build-coordinator")
+   (description "Connect to a running Guix Build Coordinator.")
+   (value (run-guix-build-coordinator-test))))
 
 
 ;;;