Now implements an asynchronous client

src/helma/xmlrpc/XmlRpcClient.java

@@ -19,8 +19,17 @@ public class XmlRpcClient implements XmlRpcHandler {
      
     URL url;
     String auth;
+    int maxThreads = 50;
 
-    /** 
+    Stack pool = new Stack ();
+    int workers = 0;
+
+    long calls = 0;
+    int roundtrip = 1000;
+
+    CallData first, last;
+
+    /**
      * Construct a XML-RPC client with this URL.
      */
     public XmlRpcClient (URL url) {
@@ -71,11 +80,15 @@ public class XmlRpcClient implements XmlRpcHandler {
      */
     public Object execute (String method, Vector params) throws XmlRpcException, IOException {
     	Worker worker = getWorker ();
+	long start = System.currentTimeMillis ();
 	try {
     	    Object retval =  worker.execute (method, params);
+	    long end = System.currentTimeMillis ();
+	    calls++;
+	    roundtrip = (int) ((roundtrip*4)+(end-start))/5;
 	    return retval;
 	} finally {
-	    worker.reset ();
+	    releaseWorker (worker);
 	}
     }
 
@@ -86,77 +99,117 @@ public class XmlRpcClient implements XmlRpcHandler {
      * 
      */
     public void executeAsync (String method, Vector params, AsyncCallback callback) {
+	if (workers > 2) {
+	    enqueue (method, params, callback);
+	    return;
+	}
     	Worker worker = null;
 	try {
 	    worker = getWorker ();
     	    worker.executeAsync (method, params, callback);
 	} catch (IOException iox) {
-	    if (callback != null)
-	        callback.handleError (iox, url, method);
+	    // make a queued worker that doesn't run immediately
+	    enqueue (method, params, callback);
 	}
     }
     
-    Stack pool = new Stack ();
-    int workers = 0;
 
-    private final Worker getWorker () throws IOException {
+    synchronized Worker getWorker () throws IOException {
 	try {
-	    return (Worker) pool.pop ();
+	    Worker w =  (Worker) pool.pop ();
+	     workers += 1;
+	     return w;
 	} catch (EmptyStackException x) {
-	    if (workers < 100) {
+	    if (workers < maxThreads) {
 	        workers += 1;
 	        return new Worker ();
 	    }
 	    throw new IOException ("XML-RPC System overload");
 	}
     }
-    
+
+   /**
+     * Release possibly big per-call object references to allow them to be garbage collected
+     */
+    synchronized void releaseWorker (Worker w) {
+	w.result = null;
+	w.call = null;
+	if (pool.size() < 20 && !w.fault)
+	    pool.push (w);
+	workers -= 1;
+    }
+
+
+    synchronized void enqueue (String method, Vector params, AsyncCallback callback) {
+	CallData call = new CallData (method, params, callback);
+	if (last == null)
+	    first = last = call;
+	else {
+	    last.next = call;
+	    last = call;
+	}
+    }
+
+    synchronized CallData dequeue () {
+	if (first == null)
+	    return null;
+	// if (workers > 2 && workers*4 > roundtrip)
+	//     return null;
+	CallData call = first;
+	if (first == last)
+	    first = last = null;
+	else
+	    first = first.next;
+	return call;
+    }
 
     class Worker extends XmlRpc implements Runnable {
 
-    String method;
-    Vector params;
     boolean fault;
     Object result = null; 
     StringBuffer strbuf;
-    AsyncCallback callback = null;
 
-    public Worker () throws IOException {
+    CallData call;
+
+    public Worker () {
     	super ();
     }
 
-    public Object execute (String method, Vector params) throws XmlRpcException, IOException {
-	this.method = method;
-	this.params = params;
-	return executeCall ();
-    }
 
     public void executeAsync (String method, Vector params, AsyncCallback callback) {
-	this.method = method;
-	this.params = params;
-	this.callback = callback;
+	this.call = new CallData (method, params, callback);
 	Thread t = new Thread (this);
 	t.start ();
     }
 
     public void run () {
+	while (call != null) {
+	    runAsync (call.method, call.params, call.callback);
+// System.err.println (workers+" ---- "+ roundtrip);
+	    call = dequeue ();
+	    // if (call != null) System.err.print (".");
+	}
+	releaseWorker (this);
+    }
+
+    void runAsync (String method, Vector params, AsyncCallback callback) {
 	Object res = null;
+	long start = System.currentTimeMillis ();
 	try {
-	    res = executeCall ();
+	    res = execute (method, params);
 	    // notify callback object
 	    if (callback != null)
 	        callback.handleResult (res, url, method);
 	} catch (Exception x) {
                  if (callback != null)
 	        callback.handleError (x, url, method);
-	} finally {
-	    reset ();
 	}
-	System.err.println ("GOT: "+result);
+	calls++;
+	long end = System.currentTimeMillis ();
+	roundtrip = (int) ((roundtrip*4)+(end-start))/5;
     }
 
-
-    private Object executeCall () throws XmlRpcException, IOException {
+    Object execute (String method, Vector params) throws XmlRpcException, IOException {
 	fault = false;
 	long now = System.currentTimeMillis ();
     	try {
@@ -246,23 +299,30 @@ public class XmlRpcClient implements XmlRpcHandler {
 	    super.startElement (name, atts);
     }
 
-    /**
-     * Release possibly big per-call object references to allow them to be garbage collected
-     */
-    public void reset () {
-	result = null;
-	params = null;
-	callback = null;
-	if (workers < 20 && !fault)
-	    pool.push (this);
-	else
-	    workers -= 1;
-
-    }
 
     } // end of inner class Worker
     
-    
+
+    class CallData {
+
+    String method;
+    Vector params;
+    AsyncCallback callback;
+    CallData next;
+
+    /**
+     * Make a call to be queued and then executed by the next free async thread
+     */
+    public CallData (String method, Vector params, AsyncCallback callback)  {
+	this.method = method;
+	this.params = params;
+	this.callback = callback;
+	this.next = null;
+    }
+
+    }
+
+
     /** 
      * Just for testing.
      */
@@ -279,7 +339,7 @@ public class XmlRpcClient implements XmlRpcHandler {
 	    }
 	    XmlRpcClient client = new XmlRpcClientLite (url);
 	    try {
-	        /* System.err.println (*/client.executeAsync (method, v, null);
+	        System.err.println (client.execute (method, v));
 	    } catch (Exception ex) {
 	        System.err.println ("Error: "+ex.getMessage());
 	    }