https://github.com/atomikos/transactions-essentials/issues/215

public/transactions-jta/src/main/java/com/atomikos/datasource/xa/session/BranchEnlistedStateHandler.java

@@ -104,4 +104,23 @@ boolean isInTransaction ( CompositeTransaction tx )
 	{
 		return ct.isSameTransaction ( tx );
 	}
+
+	// Fix by Martin Aubele. Without this fix we need one new connection per call when no 2PC is used (no propagation header).
+    // this leads to a connection shortage if the service is called multiple times. 
+
+	boolean isInactiveInTransaction ( CompositeTransaction tx ) 
+	{
+		// code is separated in special if statements to allow setting a breakpoint
+		if (ct.getCompositeCoordinator() != tx.getCompositeCoordinator())
+			return false;
+		if (ct.isRoot() != tx.isRoot())
+			return false;
+
+		// we need to check if the branch is active because of this scenario:
+		// ServiceA on Server 1 uses a jdbc connection and then calls ServiceB on Server 2. ServiceB calls
+		// back to Service A2 on Server 1. In this case, we cannot use the still ACTIVE jdbc connection.
+		if (branch.isActive())
+			return false;
+		return true;
+	}
 }

public/transactions-jta/src/main/java/com/atomikos/datasource/xa/session/SessionHandleState.java

@@ -284,9 +284,9 @@ public boolean isActiveInTransaction ( CompositeTransaction  tx )
 	public boolean isInactiveInTransaction( CompositeTransaction tx ) 
 	{
 		boolean ret = false;
-		if (closed) { // see case 159940: if not closed then be pessimistic and assume still active in terms of recycling
+		//if (closed) { // see case 159940: if not closed then be pessimistic and assume still active in terms of recycling
 			if ( currentContext != null && tx != null ) ret = currentContext.isInactiveInTransaction ( tx );
-		}
+		//}
 		return ret;
 	}
 }