redirect all HTTP 502 errors to HTTP 500 in nginx

hagrid-routes.conf

@@ -4,6 +4,14 @@
 # To protect against DOS, we limit the size of possible uploads.
 client_max_body_size 1m;
 
+# Change all HTTP 502 errors into 500, to avoid being "marked as dead" by GnuPG
+# if we ever get a spurious 502 (e.g. during a restart of hagrid).
+# See https://gitlab.com/sequoia-pgp/hagrid/issues/94
+error_page 502 =500 /502;
+location /502 {
+    return 500;
+}
+
 location /vks/v1/ {
     location ~ ^/vks/v1/by-email/([^/][^/])([^/][^/])([^/]*)$ {
         default_type application/pgp-keys;