01/02: Use advisory locks to avoid deadlocks during data deletion

[Christopher Baines]

cbaines pushed a commit to branch master
in repository data-service.

commit 38b36570132f8463cc763256aeab7613656278e6
Author: Christopher Baines <mail@cbaines.net>
AuthorDate: Mon Nov 28 10:26:46 2022 +0000

    Use advisory locks to avoid deadlocks during data deletion
    
    In the case where multiple data deleting processes end up running at the 
same
    time.
---
 guix-data-service/data-deletion.scm | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/guix-data-service/data-deletion.scm 
b/guix-data-service/data-deletion.scm
index e4762c9..6794bea 100644
--- a/guix-data-service/data-deletion.scm
+++ b/guix-data-service/data-deletion.scm
@@ -206,6 +206,10 @@ WHERE id IN (
   (with-postgresql-transaction
    conn
    (lambda (conn)
+     (obtain-advisory-transaction-lock
+      conn
+      'delete-revisions-from-branch)
+
      (delete-from-git-commits conn)
      (delete-jobs conn)
 
@@ -538,6 +542,10 @@ WHERE NOT EXISTS (
                          (with-postgresql-transaction
                           conn
                           (lambda (conn)
+                            (obtain-advisory-transaction-lock
+                             conn
+                             'delete-unreferenced-derivations)
+
                             (exec-query
                              conn
                              "