graceful handling of bad config.ru + HUP w/ preload_app

If preload_app is true and Unicorn is HUP-ed with a bad
config.ru, then it would be possible to have Unicorn in a bad
state and constantly throw 500 errors.

We now detect syntax and load errors since they're likely to
appear in modified Rackup files, and will restore the original
app if reloading failed.

1 files changed, 3 insertions, 1 deletions

diff --git a/lib/unicorn.rb b/lib/unicorn.rb
index e8d869b..6dec03e 100644
--- a/lib/unicorn.rb
+++ b/lib/unicorn.rb
@@ -731,6 +731,7 @@ module Unicorn
     end
 
     def load_config!
+      loaded_app = app
       begin
         logger.info "reloading config_file=#{config.config_file}"
         config[:listeners].replace(init_listeners)
@@ -741,9 +742,10 @@ module Unicorn
         self.app = orig_app
         build_app! if preload_app
         logger.info "done reloading config_file=#{config.config_file}"
-      rescue => e
+      rescue StandardError, LoadError, SyntaxError => e
         logger.error "error reloading config_file=#{config.config_file}: " \
                      "#{e.class} #{e.message}"
+        self.app = loaded_app
       end
     end