[JEXL-352] Possible memory leak regarding parser jjtree nodes in JEXL 3.2

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 3.2
• Fix Version/s: 3.2.1

Environment

• JEXL 3.2
• Java 11
• Jetty 9.4.41.v20210516

 

• Assignee: Henri Biestro
• Reporter: Øyvind Horneland
• Created: 14/Jun/21 08:52
• Updated: 25/Jun/21 16:25
• Resolved: 17/Jun/21 10:19

Description

Our application encountered a memory leak issue after upgrading from JEXL 3.1 to 3.2.

It seems that every call to JexlEngine createExpression now adds new entries to engine.parser.jjtree.nodes. In our case we suddenly had millions of nodes in this list.

This sample seems to reproduce the issue

JexlEngine jexlEngine = new JexlBuilder().create();
String testExpression = "dummy";

jexlEngine.createExpression(testExpression); // jexlEngine.parser.jjtree.nodes.size() == 1
jexlEngine.createExpression(testExpression); // jexlEngine.parser.jjtree.nodes.size() == 2

We currently don't cache the returned expression and JexlEngine is configured with defaults as shown in the sample.

Note that calling jexlEngine.clearCache() does not free the nodes.

Attached screenshot for the hprof of our application with ~ 1.7 million nodes in jjtree.