From e2422e358850f455100d8927483dbc35543fe706 Mon Sep 17 00:00:00 2001
From: Christopher Baines <mail@cbaines.net>
Date: Sun, 10 Oct 2021 18:10:45 +0100
Subject: Speed up storing builds

By moving looking up derivation outputs with no build to before the
transaction that writes to the database, as this will allow for more
concurrency.
---
 guix-build-coordinator/coordinator.scm | 74 ++++++++++++++++++----------------
 1 file changed, 39 insertions(+), 35 deletions(-)

diff --git a/guix-build-coordinator/coordinator.scm b/guix-build-coordinator/coordinator.scm
index 2367d40..c95099d 100644
--- a/guix-build-coordinator/coordinator.scm
+++ b/guix-build-coordinator/coordinator.scm
@@ -322,38 +322,34 @@
     (or requested-uuid
         (random-v4-uuid)))
 
-  (define (perform-datastore-changes db)
-    (unless (datastore-find-derivation datastore derivation-file)
-      (datastore-store-derivation
-       datastore
-       (read-derivation-from-file derivation-file)))
-
-    ;; Actually create a build
-    (when ensure-all-related-derivation-outputs-have-builds?
-      (let ((derivations-lacking-builds
-             (datastore-list-related-derivations-with-no-build-for-outputs
-              datastore
-              derivation-file)))
-        (for-each
-         (lambda (related-derivation)
-           (let ((related-uuid (random-v4-uuid)))
-             (simple-format #t "submtiting ~A for related ~A\n"
-                            related-uuid
-                            related-derivation)
-             (store-build related-derivation
+  (define (build-perform-datastore-changes derivations-lacking-builds)
+    (lambda (_)
+      (unless (datastore-find-derivation datastore derivation-file)
+        (datastore-store-derivation
+         datastore
+         (read-derivation-from-file derivation-file)))
+
+      (for-each
+       (lambda (related-derivation)
+         (let ((related-uuid (random-v4-uuid)))
+           (simple-format #t "submtiting ~A for related ~A\n"
                           related-uuid
-                          ;; Let the scheduler take care of
-                          ;; the prioritisation
-                          0
-                          tags)))
-         derivations-lacking-builds)))
-
-    (store-build derivation-file
-                 build-id
-                 priority
-                 tags)
-
-    #t)
+                          related-derivation)
+           (store-build related-derivation
+                        related-uuid
+                        ;; Let the scheduler take care of
+                        ;; the prioritisation
+                        0
+                        tags)))
+       derivations-lacking-builds)
+
+      ;; Actually create a build
+      (store-build derivation-file
+                   build-id
+                   priority
+                   tags)
+
+      #t))
 
   (call-with-duration-metric
    (build-coordinator-metrics-registry build-coordinator)
@@ -366,10 +362,18 @@
                   (build-for-output-already-exists?))
              '((no-build-submitted . build-already-exists-for-a-output))
              (begin
-               (datastore-call-with-transaction datastore
-                                                perform-datastore-changes
-                                                #:duration-metric-name
-                                                "store_build")
+               (datastore-call-with-transaction
+                datastore
+                (build-perform-datastore-changes
+                 (if ensure-all-related-derivation-outputs-have-builds?
+                     ;; Do this here so it doesn't take time in the writer
+                     ;; thread
+                     (datastore-list-related-derivations-with-no-build-for-outputs
+                      datastore
+                      derivation-file)
+                     '()))
+                #:duration-metric-name
+                "store_build")
 
                (build-coordinator-prompt-hook-processing-for-event
                 build-coordinator
-- 
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