Use SIGKILL/Thread#kill when the health check fails.

Author: ioquatix

fixtures/async/container/a_container.rb

@@ -201,7 +201,23 @@ module Container
 						instance.ready!
 
 						# This should trigger the health check - since restart is false, the process will be terminated:
-						sleep(2.0)
+						sleep
+					end
+					
+					container.wait
+					
+					expect(container.statistics).to have_attributes(failures: be > 0)
+				end
+				
+				it "can kill a child process even if it ignores exceptions/signals" do
+					container.spawn(health_check_timeout: 1.0) do |instance|
+						while true
+							begin
+								sleep 1
+							rescue Exception => error
+								# Ignore.
+							end
+						end
 					end
 
 					container.wait

lib/async/container/forked.rb

@@ -180,6 +180,13 @@ def terminate!
 					end
 				end
 
+				# Send `SIGKILL` to the child process.
+				def kill!
+					unless @status
+						::Process.kill(:KILL, @pid)
+					end
+				end
+				
 				# Send `SIGHUP` to the child process.
 				def restart!
 					unless @status

lib/async/container/generic.rb

@@ -172,8 +172,8 @@ def spawn(name: nil, restart: false, key: nil, health_check_timeout: nil, &block
 								when :health_check!
 									if health_check_timeout&.<(age_clock.total)
 										Console.warn(self, "Child failed health check!", child: child, age: age_clock.total, health_check_timeout: health_check_timeout)
-										# If the child has failed the health check, we assume the worst and terminate it (SIGTERM).
-										child.terminate!
+										# If the child has failed the health check, we assume the worst and kill it immediately:
+										child.kill!
 									end
 								else
 									state.update(message)

lib/async/container/threaded.rb

@@ -11,6 +11,9 @@ module Async
 	module Container
 		# A multi-thread container which uses {Thread.fork}.
 		class Threaded < Generic
+			class Kill < Exception
+			end
+			
 			# Indicates that this is not a multi-process container.
 			def self.multiprocess?
 				false
@@ -178,6 +181,14 @@ def terminate!
 					@thread.raise(Terminate)
 				end
 
+				# Invoke {Thread#kill} on the child thread.
+				def kill!
+					# Killing a thread does not raise an exception in the thread, so we need to handle the status here:
+					@status = Status.new(:killed)
+					
+					@thread.kill
+				end
+				
 				# Raise {Restart} in the child thread.
 				def restart!
 					@thread.raise(Restart)
@@ -230,7 +241,7 @@ def finished(error = nil)
 						Console.error(self) {error}
 					end
 
-					@status = Status.new(error)
+					@status ||= Status.new(error)
 					self.close_write
 				end
 			end

releases.md

@@ -1,5 +1,9 @@
 # Releases
 
+## Unreleased
+
+  - Use `SIGKILL`/`Thread#kill` when the health check fails. In some cases, `SIGTERM` may not be sufficient to terminate a process because the signal can be ignored or the process may be in an uninterruptible state.
+
 ## v0.20.1
 
   - Fix compatibility between {ruby Async::Container::Hybrid} and the health check.