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, 32 insertions, 0 deletions

diff --git a/guix-build-coordinator/datastore/sqlite.scm b/guix-build-coordinator/datastore/sqlite.scm
index bbd9c28..a6c93f3 100644
--- a/guix-build-coordinator/datastore/sqlite.scm
+++ b/guix-build-coordinator/datastore/sqlite.scm
@@ -80,6 +80,7 @@
             datastore-insert-unprocessed-hook-event
             datastore-count-unprocessed-hook-events
             datastore-list-unprocessed-hook-events
+            datastore-find-unprocessed-hook-event
             datastore-delete-unprocessed-hook-event
             datastore-list-agent-builds
             datastore-agent-for-build
@@ -2480,6 +2481,37 @@ LIMIT :limit"
 
          events)))))
 
+(define-method (datastore-find-unprocessed-hook-event
+                (datastore <sqlite-datastore>)
+                id)
+  (call-with-worker-thread
+   (slot-ref datastore 'worker-reader-thread-channel)
+   (lambda (db)
+     (let ((statement
+            (sqlite-prepare
+             db
+             "
+SELECT event, arguments
+FROM unprocessed_hook_events
+WHERE id = :id"
+             #:cache? #t)))
+
+       (sqlite-bind-arguments
+        statement
+        #:id id)
+
+       (let ((result
+              (match (sqlite-step statement)
+                (#f #f)
+                (#(event arguments)
+                 (list (string->symbol event)
+                       (call-with-input-string arguments
+                         (lambda (port)
+                           (read port))))))))
+         (sqlite-reset statement)
+
+         result)))))
+
 (define-method (datastore-delete-unprocessed-hook-event
                 (datastore <sqlite-datastore>)
                 id)