From d8ae6062b1a881f83e9dbfb12774d3548017b574 Mon Sep 17 00:00:00 2001
From: Christopher Baines <mail@cbaines.net>
Date: Sat, 24 May 2025 11:46:27 +0100
Subject: [PATCH] Retry computing channel instance manifests

On readlink errors.
---
 .../jobs/load-new-guix-revision.scm           | 44 ++++++++++++-------
 1 file changed, 27 insertions(+), 17 deletions(-)

diff --git a/guix-data-service/jobs/load-new-guix-revision.scm b/guix-data-service/jobs/load-new-guix-revision.scm
index 10ce0ea..11fc168 100644
--- a/guix-data-service/jobs/load-new-guix-revision.scm
+++ b/guix-data-service/jobs/load-new-guix-revision.scm
@@ -1570,24 +1570,34 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
                           (commit ,(channel-commit channel)))
                  ,(channel-instance-commit channel-instance)
                  ,(channel-instance-checkout channel-instance)))))
-         (simple-format
-          (current-error-port)
-          "guix-data-service: computing the derivation-file-name for ~A\n"
-          system)
 
-         (let ((manifest
-                (catch #t
-                  (lambda ()
-                    ((channel-instances->manifest instances #:system system) store))
-                  (lambda (key . args)
-                    (simple-format
-                     (current-error-port)
-                     "error: while computing manifest entry derivation for ~A\n"
-                     system)
-                    (simple-format
-                     (current-error-port)
-                     "error ~A: ~A\n" key args)
-                    #f))))
+         (define (compute)
+           (simple-format
+            (current-error-port)
+            "guix-data-service: computing the derivation-file-name for ~A\n"
+            system)
+
+           (catch #t
+             (lambda ()
+               ((channel-instances->manifest instances #:system system) store))
+             (lambda (key . args)
+               (simple-format
+                (current-error-port)
+                "error: while computing manifest entry derivation for ~A\n"
+                system)
+               (simple-format
+                (current-error-port)
+                "error ~A: ~A\n" key args)
+
+               (match (cons key args)
+                 (('system-error "readlink" _ ...)
+                  'retry)
+                 (_ #f)))))
+
+         (let loop ((manifest (compute)))
+           (when (eq? mainfest 'retry)
+             (loop (compute)))
+
            (define (add-tmp-root-and-return-drv drv)
              (add-temp-root store drv)
              drv)