Re: kawa and apache tomcat

[Per Bothner <per@bothner.com>]

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On 01/15/2016 10:10 AM, Matthieu Vachon wrote:


> This is not a problem in a standard JVM application because once the
> application closes, nothing needs to be done. But in a container
> environment, that's another story since thread a kinda re-used over
> multiple requests. On high load, this can create huge memory leaks
> depending on the what is actually stored.

As I understand it, the problem is not normal usage, but when a servlet is re-loaded.
That creates a new ClassLoader, with a new set of Classes which causes
some complicated interaction with the GC (which I don't properly understand).

In normal usage,with no ClassLoader churn, there might be some temporary leak,
but the garbage should become collectible when a thread services a new request.

Could you try the attached patch?  I haven't actually tested it (except
to verify it compiles).  Let me know if it makes a difference.
It is possible it might *reduce* the number but not eliminate the
warnings.  If so, we would be on the right track, though with more to do.

-- 
	--Per Bothner
per@bothner.com   http://per.bothner.com/

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Index: gnu/kawa/servlet/KawaServlet.java
===================================================================
--- gnu/kawa/servlet/KawaServlet.java	(revision 8666)
+++ gnu/kawa/servlet/KawaServlet.java	(working copy)
@@ -41,17 +41,9 @@
     throws ServletException, IOException
   {
     CallContext ctx = CallContext.getInstance();
-    HttpRequestContext hctx = HttpRequestContext.instance.get();
-    Context sctx;
-    if (hctx instanceof Context)
-      sctx = (Context) hctx;
-    else
-      {
-        sctx = new Context();
-        Context.setInstance(sctx);
-      }
-    sctx.init(this, request, response);
+    Context sctx = new Context(this, request, response);
     ctx.consumer = sctx.getConsumer();
+    Context.setInstance(sctx);
     // FIXME should path be relative to context?
     Path.setCurrentPath(Path.valueOf(request.getRequestURL().toString()));
     ctx.values = Values.noArgs;
@@ -100,6 +92,7 @@
       }
     finally
       {
+        Context.setInstance(null);
         sctx.servlet = null;
         sctx.request = null;
         sctx.response = null;
@@ -115,8 +108,8 @@
     ServletContext context;
     Map<String,Object> requestParameters;
 
-    public void init(HttpServlet servlet, HttpServletRequest request,
-                     HttpServletResponse response)
+    public Context(HttpServlet servlet, HttpServletRequest request,
+                   HttpServletResponse response)
     {
       if (response == null)
         throw new Error("init with null response");
@@ -317,7 +310,7 @@
     public List<String> getRequestHeaders (String name)
     {
       java.util.Enumeration<java.lang.String> e = request.getHeaders(name);
-      List<String> list = new ArrayList();
+      List<String> list = new ArrayList<String>();
       while (e.hasMoreElements())
         {
           list.add(e.nextElement());