Add a function to retry a thunk a number of times

1 files changed, 22 insertions, 0 deletions

diff --git a/guix-build-coordinator/agent-messaging/http.scm b/guix-build-coordinator/agent-messaging/http.scm
index 1fd2516..9b8b9ac 100644
--- a/guix-build-coordinator/agent-messaging/http.scm
+++ b/guix-build-coordinator/agent-messaging/http.scm
@@ -330,6 +330,28 @@ port. Also, the port used can be changed by passing the --port option.\n"
                     agent-path
                     (string-drop agent-path 1))))))
 
+(define* (retry-on-error f #:key times delay)
+  (let loop ((attempt 1))
+    (match (with-exception-handler
+               (lambda (exn)
+                 (cons #f exn))
+             (lambda ()
+               (cons #t (f)))
+             #:unwind? #t)
+      ((#t . return-value)
+       return-value)
+      ((#f . exn)
+       (if (>= attempt times)
+           (raise-exception exn)
+           (begin
+             (simple-format
+              (current-error-port)
+              "error: ~A, retrying in ~A\n"
+              exn
+              delay)
+             (sleep delay)
+             (loop (+ 1 attempt))))))))
+
 (define* (coordinator-http-request coordinator-uri agent-uuid password
                                    path
                                    #:key method body (headers '()))