Support processing hook events in parallel

Forcing hooks to be sequential simplifies them, and the implementation, but it
doesn't always scale well. I'm particularly thinking about the build-submitted
hook and built-success hooks, the processing of which can back up if there's
lots of builds being submitted or finishing successfully.

This new functionality allows hooks to be processed in parallel, which should
allow to manage this more effectively.

1 files changed, 20 insertions, 9 deletions

diff --git a/scripts/guix-build-coordinator.in b/scripts/guix-build-coordinator.in
index 1fbcad3..c9e7ee9 100644
--- a/scripts/guix-build-coordinator.in
+++ b/scripts/guix-build-coordinator.in
@@ -327,14 +327,24 @@
                            arg)
                           (exit 1)))
                     result))))
-   (map (lambda (hook)
-          (option (list (simple-format #f "~A-hook" hook)) #t #f
-                  (lambda (opt name arg result)
-                    (alist-cons (symbol-append hook '-hook)
-                                (read/eval arg)
-                                (alist-delete (symbol-append hook '-hook)
-                                              result)))))
-        %known-hooks)))
+   (append-map
+    (lambda (hook)
+      (list
+       (option (list (simple-format #f "~A-hook" hook)) #t #f
+               (lambda (opt name arg result)
+                 (alist-cons (symbol-append hook '-hook)
+                             (read/eval arg)
+                             (alist-delete (symbol-append hook '-hook)
+                                           result))))
+       (option (list (simple-format #f "~A-hook-threads" hook)) #t #f
+               (lambda (opt name arg result)
+                 (alist-cons 'parallel-hooks
+                             `((,hook . ,(string->number arg))
+                               ,@(or (assq-ref result 'parallel-hooks)
+                                     '()))
+                             (alist-delete 'parallel-hooks
+                                           result))))))
+    %known-hooks)))
 
 (define %service-option-defaults
   ;; Alist of default option values
@@ -851,4 +861,5 @@ tags:
           #:update-datastore? (assoc-ref opts 'update-database)
           #:pid-file (assq-ref opts 'pid-file)
           #:agent-communication-uri (assq-ref opts 'agent-communication)
-          #:client-communication-uri (assq-ref opts 'client-communication)))))))
+          #:client-communication-uri (assq-ref opts 'client-communication)
+          #:parallel-hooks (assq-ref opts 'parallel-hooks)))))))