From 20c1f563813a6d7b655df6b094f28a21fa306ad4 Mon Sep 17 00:00:00 2001
From: Janne Valkealahti <janne.valkealahti@gmail.com>
Date: Wed, 25 Dec 2019 07:40:26 +0000
Subject: [PATCH] Relax sync in DefaultStateMachineService

- Now starting machine outside of a sycn block with
  acquire vs. release. This should allow long running
  start in a machine to allow next acquire to work faster.
- Forwardport #770
- Relates #777
---
 .../statemachine/service/DefaultStateMachineService.java   | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/spring-statemachine-core/src/main/java/org/springframework/statemachine/service/DefaultStateMachineService.java b/spring-statemachine-core/src/main/java/org/springframework/statemachine/service/DefaultStateMachineService.java
index 5439ce30..0fb67ff8 100644
--- a/spring-statemachine-core/src/main/java/org/springframework/statemachine/service/DefaultStateMachineService.java
+++ b/spring-statemachine-core/src/main/java/org/springframework/statemachine/service/DefaultStateMachineService.java
@@ -82,8 +82,10 @@ public class DefaultStateMachineService<S, E> implements StateMachineService<S,
 	@Override
 	public StateMachine<S, E> acquireStateMachine(String machineId, boolean start) {
 		log.info("Acquiring machine with id " + machineId);
+		StateMachine<S, E> stateMachine;
+		// naive sync to handle concurrency with release
 		synchronized (machines) {
-			StateMachine<S,E> stateMachine = machines.get(machineId);
+			stateMachine = machines.get(machineId);
 			if (stateMachine == null) {
 				log.info("Getting new machine from factory with id " + machineId);
 				stateMachine = stateMachineFactory.getStateMachine(machineId);
@@ -98,8 +100,9 @@ public class DefaultStateMachineService<S, E> implements StateMachineService<S,
 				}
 				machines.put(machineId, stateMachine);
 			}
-			return handleStart(stateMachine, start);
 		}
+		// handle start outside of sync as it might take some time and would block other machines acquire
+		return handleStart(stateMachine, start);
 	}
 
 	@Override