RUBY-511 adding finalizer to jruby runtime cache to prevent runtime leaks

Author: Brandon Black

ext/jbson/src/main/jbson/RubyBSONCallback.java

@@ -320,16 +320,20 @@ protected boolean isStackEmpty() {
       return _stack.size() < 1;
     }
 
-    private static HashMap<String, Object> _getRuntimeCache(Ruby runtime) {
-      // each JRuby runtime may have different objects for these constants,
-      // so cache them separately for each runtime
+    private static HashMap<String, Object> _getRuntimeCache(final Ruby runtime) {
       @SuppressWarnings("unchecked")
       HashMap<String, Object> cache = _runtimeCache.get( runtime );
 
       if(cache == null) {
         cache = new HashMap<String, Object>();
         _runtimeCache.put( runtime, cache );
+        runtime.addFinalizer( new Finalizable() {
+          public void finalize() {
+            _runtimeCache.remove(runtime);
+          }
+        });
       }
+
       return cache;
     }
 

ext/jbson/src/main/jbson/RubyBSONEncoder.java

@@ -763,15 +763,19 @@ public void writeCString( String s ){
     private ByteBuffer _stringB = ByteBuffer.wrap( new byte[1024 + 1] );
     private CharsetEncoder _encoder = Charset.forName( "UTF-8" ).newEncoder();
 
-    private static Map _getRuntimeCache(Ruby runtime) {
-        // each JRuby runtime may have different objects for these constants,
-        // so cache them separately for each runtime
-        Map cache = (Map) _runtimeCache.get( runtime );
+    private static Map _getRuntimeCache(final Ruby runtime) {
+        Map cache = (Map) _runtimeCache.get(runtime);
 
         if(cache == null) {
             cache = new HashMap();
-            _runtimeCache.put( runtime, cache );
+            _runtimeCache.put(runtime, cache);
+            runtime.addFinalizer( new Finalizable() {
+              public void finalize() {
+                _runtimeCache.remove( runtime );
+              }
+            });
         }
+
         return cache;
     }