From 977b67e418d8ffde04c88f1b416599372fcfad94 Mon Sep 17 00:00:00 2001
From: Rossen Stoyanchev <rstoyanchev@pivotal.io>
Date: Mon, 8 Aug 2016 17:33:57 -0400
Subject: [PATCH] Protect sendHeartbeat from cancellation

Issue: SPR-14564
---
 change.diff                                                   | 0
 .../sockjs/transport/session/AbstractSockJsSession.java       | 4 ++++
 2 files changed, 4 insertions(+)
 create mode 100644 change.diff

diff --git a/change.diff b/change.diff
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractSockJsSession.java b/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractSockJsSession.java
index f2fbadeef5..dec1b4846b 100644
--- a/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractSockJsSession.java
+++ b/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractSockJsSession.java
@@ -252,6 +252,10 @@ public abstract class AbstractSockJsSession implements SockJsSession {
 		if (isActive()) {
 			if (heartbeatLock.tryLock()) {
 				try {
+					if (this.heartbeatTask == null) {
+						// Cancelled while waiting to acquire the lock
+						return;
+					}
 					writeFrame(SockJsFrame.heartbeatFrame());
 					scheduleHeartbeat();
 				}