fix: avoid ClassLoader leaks caused by SharedTimer

Avoid ClassLoader leaks caused by the TimerThread started by SharedTimer inheriting the contextClassLoader of the currently executing thread and the AccessControlContext containing ProtectionDomains with calling code.

closes #664

pgjdbc/pom.xml

@@ -3,7 +3,7 @@
   <parent>
     <groupId>org.postgresql</groupId>
     <artifactId>pgjdbc-core-parent</artifactId>
-    <version>1.1.1</version>
+    <version>1.1.2</version>
     <relativePath />
   </parent>
 

pgjdbc/src/main/java/org/postgresql/util/SharedTimer.java

@@ -30,7 +30,22 @@ public int getRefCount() {
   public synchronized Timer getTimer() {
     if (timer == null) {
       int index = timerCount.incrementAndGet();
-      timer = new Timer("PostgreSQL-JDBC-SharedTimer-" + index, true);
+
+      /*
+       Temporarily switch contextClassLoader to the one that loaded this driver to avoid TimerThread preventing current
+       contextClassLoader - which may be the ClassLoader of a web application - from being GC:ed.
+       */
+      final ClassLoader prevContextCL = Thread.currentThread().getContextClassLoader();
+      try {
+        /*
+         Scheduled tasks whould not need to use .getContextClassLoader, so we just reset it to null
+         */
+        Thread.currentThread().setContextClassLoader(null);
+
+        timer = new Timer("PostgreSQL-JDBC-SharedTimer-" + index, true);
+      } finally {
+        Thread.currentThread().setContextClassLoader(prevContextCL);
+      }
     }
     refCount.incrementAndGet();
     return timer;

pgjdbc/src/test/java/org/postgresql/test/util/SharedTimerClassLoaderLeakTest.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2016, PostgreSQL Global Development Group
+ * See the LICENSE file in the project root for more information.
+ */
+
+package org.postgresql.test.util;
+
+import org.postgresql.Driver;
+
+import org.junit.After;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import se.jiderhamn.classloader.PackagesLoadedOutsideClassLoader;
+import se.jiderhamn.classloader.leak.JUnitClassloaderRunner;
+import se.jiderhamn.classloader.leak.Leaks;
+
+/**
+ * Test case that verifies that the use of {@link org.postgresql.util.SharedTimer} within
+ * {@link org.postgresql.Driver} does not cause ClassLoader leaks
+ * @author Mattias Jiderhamn
+ */
+@RunWith(JUnitClassloaderRunner.class)
+@PackagesLoadedOutsideClassLoader(packages = "org.postgresql", addToDefaults = true)
+public class SharedTimerClassLoaderLeakTest {
+
+  /** Starting a {@link org.postgresql.util.SharedTimer} should not cause ClassLoader leaks */
+  @Leaks(false)
+  @Test
+  public void sharedTimerDoesNotCauseLeak() {
+    Driver.getSharedTimer().getTimer(); // Start timer
+  }
+
+  @After
+  public void tearDown() {
+    Driver.getSharedTimer().releaseTimer();
+  }
+}

pom.xml

@@ -3,7 +3,7 @@
   <parent>
     <groupId>org.postgresql</groupId>
     <artifactId>pgjdbc-versions</artifactId>
-    <version>1.1.1</version>
+    <version>1.1.2</version>
   </parent>
 
   <artifactId>pgjdbc-aggregate</artifactId>

ubenchmark/pom.xml

@@ -31,7 +31,7 @@ POSSIBILITY OF SUCH DAMAGE.
   <parent>
     <groupId>org.postgresql</groupId>
     <artifactId>pgjdbc-versions</artifactId>
-    <version>1.1.1</version>
+    <version>1.1.2</version>
     <relativePath />
   </parent>