Log and handle any exceptions on process exit

Author: akadusei

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Added
 - Add `Signal::HUP` to `Mel.stop` signals
 - Add Windows support to signal handlers
+- Log and handle any exceptions on process exit
 
 ### Fixed
 - Synchronize `Mel.state` reads with writes

src/mel.cr

@@ -28,6 +28,7 @@ module Mel
 
   extend self
 
+  include Helpers
   include LogHelpers
 
   @@mutex = Mutex.new(:reentrant)
@@ -131,6 +132,8 @@ module Mel
     {% else %}
       {Signal::HUP, Signal::INT, Signal::TERM}.each &.trap { stop }
     {% end %}
+
+    at_exit { |code, error| handle_exit(code, error) }
   end
 
   private def batch_size(pond)

src/mel/helpers.cr

@@ -3,5 +3,13 @@ module Mel::Helpers
     private def handle_error(error) : Nil
       Mel.settings.error_handler.call(error)
     end
+
+    private def handle_exit(code, error) : Nil
+      message = "Mel exited with code #{code}"
+      return Mel.log.info &.emit(message) if code == 0 && error.nil?
+
+      Mel.log.fatal(exception: error, &.emit(message))
+      handle_error(error) if error
+    end
   end
 end