Record job success without deleting the job record

Previously, the records for jobs would be deleted. It's useful to know when
jobs were inserted in to the database, as well as when they succeeded (if they
have). This change also makes it possible to keep track of jobs that have
failed, as they won't be deleted.

guix-data-service/jobs/load-new-guix-revision.scm

@@ -385,13 +385,15 @@
 
           (simple-format
            #t "Successfully loaded ~A package/derivation pairs\n"
-           (length package-derivation-ids))))
+           (length package-derivation-ids)))
+        #t)
       (lambda (key . args)
         (simple-format (current-error-port)
                        "Failed extracting information: ~A ~A\n"
                        key args)
         (force-output)
-        (exec-query conn "ROLLBACK")))))
+        (exec-query conn "ROLLBACK")
+        #f))))
 
 (define (load-new-guix-revision conn git-repository-id commit)
   (if (guix-revision-exists? conn git-repository-id commit)
@@ -440,6 +442,14 @@ RETURNING id;")
           (list (number->string n)))))
     result))
 
+(define (record-job-succeeded conn id)
+  (exec-query
+   conn
+   (string-append
+    "UPDATE load_new_guix_revision_jobs WHERE id = $1 "
+    "SET succeeded_at = current_time")
+   (list id)))
+
 (define (process-next-load-new-guix-revision-job conn)
   (let ((next
          (exec-query
@@ -452,10 +462,7 @@ RETURNING id;")
        (begin
          (simple-format #t "Processing job ~A (commit: ~A, source: ~A)\n\n"
                         id commit source)
-         (load-new-guix-revision conn git-repository-id commit)
-         (exec-query
-          conn
-          (string-append "DELETE FROM load_new_guix_revision_jobs WHERE id = '"
-                         id
-                         "'"))))
+         (when (eq? (load-new-guix-revision conn git-repository-id commit)
+                    #t)
+           (record-job-succeeded conn id))))
       (_ #f))))