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Higher memory usage, blocked thread when using vertx circuit breaker

Context
I am getting high memory usage with the vertx circuit breaker. I am just using httpbin.org to get all success responses. For individual requests, it works fine. While running a load test the JVM old gen utilization is spiking up.
Reproducer
I have the main verticle code, pasting it here itself:
public class CleanServer extends AbstractVerticle {
Logger logger = Logger.getLogger(CleanServer.class.getName());
#Override
public void start(Promise<Void> startPromise) throws Exception {
Router router = Router.router(vertx);
CircuitBreakerCache cbc = new CircuitBreakerCache(vertx);
router.route(HttpMethod.GET, "/get").handler(context -> {
List<String> domains = context.queryParam("user");
String domain = domains.get(0);
CircuitBreaker cb = cbc.getCircuitBreaker(domain + context.request().path());
HttpServerResponse serverResponse =
context.response().setChunked(true);
cb.executeWithFallback(promise -> {
WebClientOptions options = new WebClientOptions().setTryUseCompression(true).setTcpNoDelay(true).setTcpCork(true).setReceiveBufferSize(128).setConnectTimeout(400);
WebClient client = WebClient.create(vertx, options);
client.get(80, "httpbin.org", "/status/200")
.timeout(2000)
.send(ar -> {
if (ar.succeeded()) {
HttpResponse<Buffer> response = ar.result();
int statusCode = response.statusCode();
if (statusCode != 200) {
promise.fail(response.statusMessage());
} else {
serverResponse.end("Hello!!");
promise.complete();
}
} else {
promise.fail(ar.cause().getMessage());
}
});
}, v -> {
// Executed when the circuit is opened
logger.log(Level.INFO, domain + " Failed " + cb.state().toString() + " Error: Circuit open");
serverResponse.setStatusCode(200).setStatusMessage("Circuit Open").end("Circuit Open");
return context;
});
});
// Create the HTTP server
vertx.createHttpServer(new HttpServerOptions().setMaxInitialLineLength(10000))
// Handle every request using the router
.requestHandler(router)
// Start listening
.listen(8080)
// Print the port
.onSuccess(server ->
System.out.println(
"HTTP server started on port " + server.actualPort()
)
);
}
}
Circuit breaker options:
CircuitBreakerOptions()
.setMaxFailures(50)
.setTimeout(5000)
.setFallbackOnFailure(true)
.setResetTimeout(10000)));
Steps to reproduce
API used: http://localhost:8080/get?user=abc
When I hit the above API at 50 QPS for 30 minutes. The java heap is getting filled up.
Extra
<vertx.version>4.2.6</vertx.version>
JVM params used:
-XX:+UseG1GC -Xms4g -Xmx4g -XX:InitiatingHeapOccupancyPercent=70 -XX:MaxGCPauseMillis=200 -XX:ParallelGCThreads=20 -XX:ConcGCThreads=5
JVM memory with the load test.
Error:
WARNING: Thread Thread[vert.x-eventloop-thread-3,5,main] has been blocked for 3050 ms, time limit is 2000 ms
I think I am blocking the thread somewhere but not sure where exactly as the code seems pretty simple as given in the documentation.

uWebSockets concurrent sessions

for the sake of simplicity, let's assume I have only one uWebSockets instance running on my server:
struct UserData
{
uWS::WebSocket<true, uWS::SERVER> *ws;
bool logged_in = false;
ID user_id;
};
uWS::SSLApp()
.ws<UserData>(
"/*",
{
.open =
[](auto *ws, auto *req) {
std::cout << "user with ip: " << ws->getRemoteAddress()
<< " connected" << std::endl;
},
.message =
[](auto *ws, std::string_view message,
uWS::OpCode opCode) {
auto userData = static_cast<UserData *>(ws->getUserData());
// give websocket pointer to a session
userData->ws = ws;
Session session;
session.process_message(userData, message);
}
.listen(9001,
[](auto *token) {
if (token)
std::cout << "listening on port 9001" << std::endl;
else
std::cout << "failed to listen on port 9001" << std::endl;
})
.run();
});
possible implementation of Session:
class Session {
process_message(UserData &userData, const std::string_view &message) {
std::this_thread::sleep_for(std::chrono::seconds(1));
}
}
inside the function Session::process_message, I have a code that takes a long time to finish.
How do I return control to the event loop in order for it to process some other sessions?
In other words, how do I design the program to be fully asynchronous/run session concurrently?
The library is asynchronous.
does it mean that the library will handle the other connections concurrently and I have nothing to worry about?

During the sleep, uWebSockets will not process other network connections.
Change the sleep to fast code that only gets a mutex, adds to a queue, and releases a mutex.
Make another thread (let's call it ProcessingThread) that gets the same mutex, removes messages from that queue, releases the mutex, and processes the messages. ProcessingThread may take as long as it needs to process messages without slowing down the uWebSockets thread.

Boost::asio::async_read_until never calls handler

I am trying to build a connection between two computers on a local network, one using a slightly modified version of the Boost Asio C++ TCP asynchronous server sample, the other one using NodeJS.
tcp_client.js :
var net = require('net');
var HOST = '127.0.0.1';
var PORT = 14002;
var client = new net.Socket();
client.connect(PORT, HOST, function() {
console.log('CONNECTED TO: ' + HOST + ':' + PORT);
// Write a message to the socket as soon as the client is connected
//the server will receive it as message from the client
client.write('Hello');
});
// Add a 'data' event handler for the client socket
// data is what the server sent to this socket
client.on('data', function(data) {
var fs = require('fs');
fs.writeFile("test.txt", data, function(err) {
if(err) {
return console.log(err);
}
client.write("Data written"); // returns successful
console.log("The file was saved!");
});
});
// Add a 'close' event handler for the client socket
client.on('close', function() {
console.log('Connection closed');
});
tcpServer.cpp :
#include <ctime>
#include <iostream>
#include <fstream>
#include <string>
#include <unistd.h>
#include <boost/bind.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <boost/asio.hpp>
extern string _coordinates;
using namespace std;
using boost::asio::ip::tcp;
std::string inline make_daytime_string() {
std:: time_t now = std::time(0);
return std::ctime(&now);
}
class tcp_connection
// Using shared_ptr and enable_shared_from_this
// because we want to keep the tcp_connection object alive
// as long as there is an operation that refers to it.
: public boost::enable_shared_from_this<tcp_connection>
{
public:
typedef boost::shared_ptr<tcp_connection> pointer;
static pointer create(boost::asio::io_service& io_service) {
cout << "Creates a pointer for the tcp connection" <<endl;
return pointer(new tcp_connection(io_service));
}
tcp::socket& socket() {
return socket_;
}
// Call boost::asio::async_write() to serve the data to the client.
// We are using boost::asio::async_write(),
// rather than ip::tcp::socket::async_write_some(),
// to ensure that the entire block of data is sent.
void start() {
while(1) {
start_read();
// This is going to read after every 1ms the _coordinates variable
usleep(1000);
m_message = _coordinates;
boost::asio::async_write(
socket_,
boost::asio::buffer(m_message),
boost::bind(
&tcp_connection::handle_write,
shared_from_this(),
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred
)
);
}
}
private:
tcp_connection(boost::asio::io_service& io_service)
: socket_(io_service)
{
}
void start_read() {
// Start an asynchronous operation to read a newline-delimited message.
// When read, handle_read should kick in
boost::asio::async_read_until(
socket_,
input_buffer_,
'\n',
boost::bind(
&tcp_connection::handle_read,
shared_from_this(),
boost::asio::placeholders::error
)
);
}
// When stream is received, handle the message from the client
void handle_read(const boost::system::error_code& ec) {
std::cout << "HANDLE_READ - line 101" << "\n";
messageFromClient_ = "";
if (!ec) {
// Extract the newline-delimited message from the buffer.
std::string line;
std::istream is(&input_buffer_);
std::getline(is, line);
// Empty messages are heartbeats and so ignored.
if (!line.empty()) {
messageFromClient_ += line;
std::cout << "Received: " << line << "\n";
}
start_read();
}
else {
std::cout << "Error on receive: " << ec.message() << "\n";
}
}
// handle_write() is responsible for any further actions
// for this client connection.
void handle_write(const boost::system::error_code& /*error*/, size_t /*bytes_transferred*/) {
m_message += "helloo\n";
}
tcp::socket socket_;
std::string m_message;
boost::asio::streambuf input_buffer_;
std::string messageFromClient_;
};
class tcp_server {
public:
// Constructor: initialises an acceptor to listen on TCP port 14002.
tcp_server(boost::asio::io_service& io_service)
: acceptor_(io_service, tcp::endpoint(tcp::v4(), 14002))
{
// start_accept() creates a socket and
// initiates an asynchronous accept operation
// to wait for a new connection.
start_accept();
}
private:
void start_accept() {
// creates a socket
cout << "creating a new socket for the communication" <<endl;
tcp_connection::pointer new_connection = tcp_connection::create(acceptor_.get_io_service());
// initiates an asynchronous accept operation
// to wait for a new connection.
acceptor_.async_accept(
new_connection->socket(),
boost::bind(
&tcp_server::handle_accept,
this,
new_connection,
boost::asio::placeholders::error
)
);
}
// handle_accept() is called when the asynchronous accept operation
// initiated by start_accept() finishes. It services the client request
void handle_accept(tcp_connection::pointer new_connection, const boost::system::error_code& error) {
if (!error) {
cout << "Starting the new tcp connection" <<endl;
new_connection->start();
}
// Call start_accept() to initiate the next accept operation.
start_accept();
}
tcp::acceptor acceptor_;
};
int inline launch_server() {
try {
boost::asio::io_service io_service;
tcp_server server(io_service);
// Run the io_service object to perform asynchronous operations.
io_service.run();
}
catch (std::exception& e) {
std::cerr << e.what() << std::endl;
}
return 0;
}
Sending the message from the C++ to NodeJS works (the async_write(..) in the start() while loop, which sends _coordinates every 1ms), but I can't manage to handle the messages coming from my NodeJS program :
When running (both programs on my computer, on localhost), the output of ss -tp | grep 14002 (14002 being the port), the Recv-Q/Send-Q of the NodeJS process are empty (and the socket.write(...) returns successful), while, for the C++ part, the Recv-Q is constantly growing and Send-Q is empty
Moreover, when running, all the cout .. of the handler_read() are not printed, which means that the async_read_until() function never calls the handler.
I tried all the overload versions of the async_read_until(), none of them works. And, as the messages are not of constant size, it seems that i have no choice but to use read_until.
I hope I didn't forget any useful information. Thank you for your help !

You are basically saturating your CPU with the infinite while loop in your tcp_connection::start method. Not only that it is saturating the CPU, it is also a bug in your design. Why would you want to continuously attach handlers for read and also send/write data to the socket in a infinite loop ? Most probably you want to write to the socket after receiving a request from the client.
Below are the methods I changed to make it work like a regular client-server:
void start() {
start_read();
// This is going to read after every 1ms the _coordinates variable
usleep(1000);
m_message = _coordinates;
}
void start_read() {
// Start an asynchronous operation to read a newline-delimited message.
// When read, handle_read should kick in
boost::asio::async_read_until(
socket_,
input_buffer_,
'\n',
boost::bind(
&tcp_connection::handle_read,
shared_from_this(),
boost::asio::placeholders::error
)
);
}
void handle_read(const boost::system::error_code& ec) {
std::cout << "HANDLE_READ - line 101" << "\n";
messageFromClient_ = "";
if (!ec) {
// Extract the newline-delimited message from the buffer.
std::string line;
std::istream is(&input_buffer_);
std::getline(is, line);
// Empty messages are heartbeats and so ignored.
if (!line.empty()) {
messageFromClient_ += line;
std::cout << "Received: " << line << "\n";
}
start_read();
}
else {
std::cout << "Error on receive: " << ec.message() << "\n";
}
start_read();
boost::asio::async_write(
socket_,
boost::asio::buffer(m_message),
boost::bind(
&tcp_connection::handle_write,
shared_from_this(),
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred
)
);
}
I am not sure what you are 'actually' trying to do based on the question as it stands now, but the above changes should be a good point to start with.

WebSocket - Invalid status line javascript

I'm running a spring 3.1.2 backend on a weblogic 12.1.3 server.
In order to accept websocket connections, my configurator as follows:
public class SpringConfigurator extends Configurator {
private static final Logger LOGGER = LoggerFactory.make();
private static final Map<String, Map<Class<?>, String>> cache = new ConcurrentHashMap<String, Map<Class<?>, String>>();
private static final String MAGIC_STR = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
private static final String NO_VALUE = ObjectUtils.identityToString(new Object());
#SuppressWarnings("unchecked")
#Override
public <T> T getEndpointInstance(Class<T> endpointClass) throws InstantiationException {
WebApplicationContext wac = ContextLoader.getCurrentWebApplicationContext();
if (wac == null) {
String message = "Failed to find the root WebApplicationContext. Was ContextLoaderListener not used?";
LOGGER.error(message);
throw new IllegalStateException(message);
}
String beanName = ClassUtils.getShortNameAsProperty(endpointClass);
if (wac.containsBean(beanName)) {
T endpoint = wac.getBean(beanName, endpointClass);
if (LOGGER.isTraceEnabled()) {
LOGGER.trace("Using #ServerEndpoint singleton " + endpoint);
}
return endpoint;
}
Component annot = AnnotationUtils.findAnnotation(endpointClass, Component.class);
if ((annot != null) && wac.containsBean(annot.value())) {
T endpoint = wac.getBean(annot.value(), endpointClass);
if (LOGGER.isTraceEnabled()) {
LOGGER.trace("Using #ServerEndpoint singleton " + endpoint);
}
return endpoint;
}
beanName = getBeanNameByType(wac, endpointClass);
if (beanName != null) {
return (T) wac.getBean(beanName);
}
if (LOGGER.isTraceEnabled()) {
LOGGER.trace("Creating new #ServerEndpoint instance of type " + endpointClass);
}
return wac.getAutowireCapableBeanFactory().createBean(endpointClass);
}
// modifyHandshake() is called before getEndpointInstance()
#Override
public void modifyHandshake(ServerEndpointConfig sec, HandshakeRequest request, HandshakeResponse response) {
super.modifyHandshake(sec, request, response);
}
private String getBeanNameByType(WebApplicationContext wac, Class<?> endpointClass) {
String wacId = wac.getId();
Map<Class<?>, String> beanNamesByType = cache.get(wacId);
if (beanNamesByType == null) {
beanNamesByType = new ConcurrentHashMap<Class<?>, String>();
cache.put(wacId, beanNamesByType);
}
if (!beanNamesByType.containsKey(endpointClass)) {
String[] names = wac.getBeanNamesForType(endpointClass);
if (names.length == 1) {
beanNamesByType.put(endpointClass, names[0]);
} else {
beanNamesByType.put(endpointClass, NO_VALUE);
if (names.length > 1) {
String message = "Found multiple #ServerEndpoint's of type " + endpointClass + ", names=" + names;
LOGGER.error(message);
throw new IllegalStateException(message);
}
}
}
String beanName = beanNamesByType.get(endpointClass);
return NO_VALUE.equals(beanName) ? null : beanName;
}
}
The problem is when I try to open websocket connection via a javascript client, it correctly generates response headers as I debugged this location:
#Override
public void modifyHandshake(ServerEndpointConfig sec, HandshakeRequest request, HandshakeResponse response) {
super.modifyHandshake(sec, request, response);
}
But in client side it gives following error:
WebSocket connection to 'ws://localhost:7001/websocket' failed: Error during >WebSocket handshake: Invalid status line
In chrome developer tools the response seems as follows:
HTTP/0.9 200 OK
I think somehow http request does not upgrade to websocket connection.
I really appreciate any help regarding this issue.

I encountered exactly this issue today when testing http://showcase.omnifaces.org/push/socket on WebLogic 12.2.1.
Already at the first test attempt of the webapp, WebLogic throws the below exception when making a websocket connection:
java.lang.IllegalStateException: The async-support is disabled on this request: weblogic.servlet.internal.ServletRequest
Impl#6682044b[GET /omnifaces.push/counter?e6845a3a-26ed-4520-9824-63ffd85b24eb HTTP/1.1]
at weblogic.servlet.internal.ServletRequestImpl.startAsync(ServletRequestImpl.java:1949)
at weblogic.servlet.internal.ServletRequestImpl.startAsync(ServletRequestImpl.java:1925)
at javax.servlet.ServletRequestWrapper.startAsync(ServletRequestWrapper.java:432)
at weblogic.websocket.tyrus.TyrusServletFilter.doFilter(TyrusServletFilter.java:234)
...
It turns out that, on contrary to all other servers I tested, WebLogic's own TyrusServletFilter, which is responsible for handling websocket handshake requests, is internally installed after the filters provided via web.xml of the deployed webapp. The webapp shipped with a character encoding filter and a GZIP filter mapped on /*, so they were invoked before the websocket filter. This was strange at first sight, but I thought it is what it is, so I just added <async-supported>true</async-supported> to those webapp-provided filters so that the TyrusServletFilter can do its job.
However, when making a websocket connection, a JavaScript error in the client side occurred when a push message was being sent, exactly the one you faced:
WebSocket connection to 'ws://localhost:7001/omnifaces.push/counter?e6845a3a-26ed-4520-9824-63ffd85b24eb' failed: Error during WebSocket handshake: Invalid status line
It turns out that WebSockets just can't deal with GZIP responses. After disabling the GZIP filter, everything continued to work flawlessly.
The root problem is however that WebLogic should have installed its TyrusServletFilter before all webapp-provided filters. All other Java EE servers I ever have tested do this correctly. Your workaround of immediately dispatching and forwarding all websocket handshake requests to their target URL pattern, as mentioned in your comment on the question, is a good one. The alternative would be to reconfigure the web.xml-provided filters to not match websocket handshake requests anymore, e.g. by using a more specific URL pattern, or mapping to a specific servlet instead.

PNaCl - How do i post message from index.html to PNaCl?

I run the hello_nacl example of nacl_sdk(pepper_39) and everything is fine.
But i try adding something on index.html to post message to PNaCl, it's not work and get error like this "NativeClient: NaCl module crashed".
This is my index.html, anyone can tell me what's wrong?
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Pragma" content="no-cache">
<meta http-equiv="Expires" content="-1">
<script type="text/javascript">
var HelloTutorialModule = null;
function pageDidLoad() {
appendStatus('Page loaded');
HelloTutorialModule = document.getElementById('nacl_module');
HelloTutorialModule.postMessage('hello from HTML!!');
}
function appendStatus(opt_message) {
var statusField = document.getElementById('statusField');
if (statusField) {
var newElt = document.createElement("opt_message");
newElt.innerHTML = "<br>" + opt_message;
statusField.appendChild(newElt);
}
}
function handleMessage(message_event) {
appendStatus(message_event.data);
}
</script>
</head>
<body>
<div id="listener">
<script type="text/javascript">
var listener = document.getElementById('listener');
listener.addEventListener('message', handleMessage, true);
listener.addEventListener('load', pageDidLoad, true);
</script>
<h2>NaCl Module</h2>
<embed name="nacl_module"
id="nacl_module"
style="border-style: solid;"
width=200
height=200
src="newlib/hello_nacl.nmf"
type="application/x-nacl"/>
</div>
Thank you.
The following code is my hello_nacl.c
/* Copyright (c) 2012 The Chromium Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
// This project demonstrates how to migrate a Windows desktop app to Native
// Client, running first as a Win32 application (define STEP1), then as a PPAPI
// plugin (define STEP2 through STEP6), and finally as a Native Client module.
// Start with STEP1 defined and the defines for STEP2 through STEP6 commented
// out. For each step in the process, un-comment the next #define, leaving the
// previous ones on. Ready, set, port!
// *** SELECT THE WIN32 PLATFORM AND RUN WITH #define STEP1 ONLY ***
// #define STEP1
// Launches the original Windows desktop application, Hello World, which runs
// as WinMain. STEP1 encloses Windows-specific functions that are used with
// the WIN32 and PPAPI platforms. These will be removed when the full PPAPI
// port is finished (STEP6)
// *** SELECT THE PPAPI PLATFORM ***
#define STEP2
// What Changed: The platform launches Chrome, which will then load a Native
// Client Module. STEP2 encloses the Native Client module APIs needed to link
// any app to the browser. The module does nothing except report
// starting/ending the function Instance_DidCreate. The Windows app does not
// run because it is not being called.
#define STEP3
// What changed: Replace WinMain with WndProc, and call it from
// Instance_DidCreate, launching hello_nacl in its own window.
// Since WndProc spins in its message loop, the call to Instance_DidCreate
// never returns.
// Close the hello_nacl window and the module initialization will finish.
#define STEP4
// What changed: In WndProc replace the message loop with a callback function.
// Now the app window and the Native Client module are running concurrently.
#define STEP5
// What changed: Instance_DidCreate calls InitInstanceInBrowserWindow rather
// than InitInstanceInPCWindow.
// The InitInstanceInBrowserWindow uses postMessage to place text (now "Hello,
// Native Client") in the web page instead of opening and writing to a window.
#define STEP6
// What changed: All the Windows code is def'd out, to prove we are
// PPAPI-compliant. The functional code that is running is the same as STEP5.
// *** SELECT THE NACL64 PLATFORM AND RUN ***
// What changed: The code is the same as STEP6, but you are using the SDK
// toolchain to compile it into a nexe. The module is now running as a real
// Native Client executable in a NaCl sandbox, with nacl-gdb attached.
// *** RUN YOUR MODULE IN THE WILD ***
// You can run your nexe outside of Visual Studio, directly from Chrome by
// following these steps:
// - Build STEP6 and verify the file
// <project directory>/NaCl64/newlib/Debug/hello_nacl_64.nexe exists
// - Copy the folder <project directory> into your NaCl SDK's example
// directory.
// - Go to the NaCl SDK directory and launch the httpd.py server.
// - Launch Chrome, go to about:flags and enable the Native Client flag and
// relaunch Chrome
// - Point Chrome at http: //localhost:5103/hello_nacl
#ifdef STEP6
// remove Windows-dependent code.
#undef STEP1
#undef STEP3
#undef STEP4
#define NULL 0
#else
// includes for Windows APIs.
#include <windows.h>
#include <stdlib.h>
#include <tchar.h>
#endif
#ifdef STEP2
// includes for PPAPI
#include "ppapi/c/pp_errors.h"
#include "ppapi/c/pp_module.h"
#include "ppapi/c/pp_var.h"
#include "ppapi/c/ppb.h"
#include "ppapi/c/ppb_instance.h"
#include "ppapi/c/ppb_messaging.h"
#include "ppapi/c/ppb_var.h"
#include "ppapi/c/ppb_core.h"
#include "ppapi/c/ppp.h"
#include "ppapi/c/ppp_instance.h"
#include "ppapi/c/ppp_messaging.h"
#include <string.h>
#include <stdio.h>
#include <time.h>
// Native Client APIs
static PPB_Messaging* ppb_messaging_interface = NULL;
static PPB_Var* ppb_var_interface = NULL;
static PPB_Core* ppb_core_interface = NULL;
PP_Instance myInstance;
int InitInstanceInPCWindow();
void InitInstanceInBrowserWindow();
#endif
#ifdef STEP4
// Implements message handling in a callback function.
void HelloWorldCallbackFun(void* user_data, int32_t result);
struct PP_CompletionCallback HelloWorldCallback = {
HelloWorldCallbackFun, NULL };
void HelloWorldCallbackFun(void* user_data, int32_t result) {
MSG uMsg;
if (PeekMessage(&uMsg, NULL, 0, 0, PM_REMOVE)) {
TranslateMessage(&uMsg);
DispatchMessage(&uMsg);
}
ppb_core_interface->CallOnMainThread(100, HelloWorldCallback, 0);
}
#endif
#ifdef STEP2
// The basic framework needed for all Native Client Modules. Handles creation
// of the module instance and initial handshake with the browser.
/**
* Creates new string PP_Var from C string. Useful utility for
* message-handling.
*/
static struct PP_Var CStrToVar(const char* str) { if (ppb_var_interface !=
NULL) { return ppb_var_interface->VarFromUtf8(str, strlen(str)); } return
PP_MakeUndefined(); }
void InitInstanceInBrowserWindow() {
// Pass the text to the browser page, there is no separate app window
// anymore. The text is added as a new element to the page, it does not
// appear in the module's embed view.
ppb_messaging_interface->PostMessage(myInstance, CStrToVar("Hello, Native Client! XDDXDXD"));
}
/**
* Called when the NaCl module is instantiated on the web page.
*/
static PP_Bool Instance_DidCreate(PP_Instance instance,
uint32_t argc,
const char* argn[],
const char* argv[]) {
myInstance = instance;
ppb_messaging_interface->PostMessage(instance,
CStrToVar("Start Instance_DidCreate"));
#ifdef STEP5
// Will be included in STEP5 and STEP6
// Uses messaging to relay text to the module's view on the web page
InitInstanceInBrowserWindow();
#else
#ifdef STEP3
// Will be included in STEP3 and STEP4 only
// Uses WndProc to place text in a window separate from the browser.
InitInstanceInPCWindow();
#endif
#endif
ppb_messaging_interface->PostMessage(instance,
CStrToVar("End Instance_DidCreate"));
return PP_TRUE;
}
/**
* Called when the NaCl module is destroyed.
*/
static void Instance_DidDestroy(PP_Instance instance) {
ppb_messaging_interface->PostMessage(instance,
CStrToVar("Instance_DidDestroy"));
}
/**
* Called when the position, the size, or the clip rect of the element in the
* browser that corresponds to this NaCl module has changed.
*/
static void Instance_DidChangeView(PP_Instance instance,
PP_Resource view_resource) {
ppb_messaging_interface->PostMessage(instance,
CStrToVar("Instance_DidChangeView"));
}
/**
* Notification that the given NaCl module has gained or lost focus.
*/
static void Instance_DidChangeFocus(PP_Instance instance,
PP_Bool has_focus) {
ppb_messaging_interface->PostMessage(instance,
CStrToVar("Instance_DidChangeFocus"));
}
/**
* Handler that gets called after a full-frame module is instantiated based on
* registered MIME types. This function is not called on NaCl modules. This
* function is essentially a place-holder for the required function pointer in
* the PPP_Instance structure.
*/
static PP_Bool Instance_HandleDocumentLoad(PP_Instance instance,
PP_Resource url_loader) {
/* NaCl modules do not need to handle the document load function. */
ppb_messaging_interface->PostMessage(instance,
CStrToVar("Instance_HandleDocumentLoad...."));
return PP_FALSE;
}
static void HandleMessage(PP_Instance instance, struct PP_Var message){
//ppb_messaging_interface->PostMessage(instance, CStrToVar("Get Message From HTML"));
}
/**
* Entry points for the module.
* Initialize needed interfaces: PPB_Core, PPB_Messaging and PPB_Var.
*/
PP_EXPORT int32_t PPP_InitializeModule(PP_Module a_module_id,
PPB_GetInterface get_browser) {
ppb_messaging_interface = (PPB_Messaging*)
get_browser(PPB_MESSAGING_INTERFACE);
ppb_var_interface = (PPB_Var*)get_browser(PPB_VAR_INTERFACE);
ppb_core_interface = (PPB_Core*)get_browser(PPB_CORE_INTERFACE);
return PP_OK;
}
/**
* Returns an interface pointer for the interface of the given name, or NULL
* if the interface is not supported.
*/
PP_EXPORT const void* PPP_GetInterface(const char* interface_name) {
if (strcmp(interface_name, PPP_INSTANCE_INTERFACE) == 0) {
static PPP_Instance instance_interface = {
&Instance_DidCreate,
&Instance_DidDestroy,
&Instance_DidChangeView,
&Instance_DidChangeFocus,
&Instance_HandleDocumentLoad,
//&HandleMessage,
};
return &instance_interface;
}
return NULL;
}
/**
* Called before the plugin module is unloaded.
*/
PP_EXPORT void PPP_ShutdownModule() {
}
#endif
// **** Application Code ****
#ifdef STEP1
// Desktop Windows Hello World app. Native Client agnostic.
static TCHAR szWindowClass[] = _T("win32app");
static TCHAR szTitle[] = _T("hello_nacl");
HINSTANCE hInst;
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
// WinMain
int WINAPI WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow) {
WNDCLASSEX wcex;
HWND hWnd;
MSG msg;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInstance;
wcex.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_APPLICATION));
wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wcex.lpszMenuName = NULL;
wcex.lpszClassName = szWindowClass;
wcex.hIconSm = LoadIcon(wcex.hInstance,
MAKEINTRESOURCE(IDI_APPLICATION));
if (!RegisterClassEx(&wcex)) {
MessageBox(NULL,
_T("Call to RegisterClassEx failed!"),
_T("hello_nacl"),
0);
return 1;
}
hInst = hInstance;
hWnd = CreateWindow(
szWindowClass,
szTitle,
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT,
500, 100,
NULL,
NULL,
hInstance,
NULL);
if (!hWnd) {
MessageBox(NULL,
_T("Call to CreateWindow failed!"),
_T("hello_nacl"),
0);
return 1;
}
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);
// Main message loop:
while (GetMessage(&msg, NULL, 0, 0)) {
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return (int) msg.wParam;
}
// WndProc
LRESULT CALLBACK WndProc(HWND hWnd, UINT message,
WPARAM wParam, LPARAM lParam) {
PAINTSTRUCT ps;
HDC hdc;
TCHAR greeting[] = _T("Hello, World!");
switch (message) {
case WM_PAINT:
hdc = BeginPaint(hWnd, &ps);
TextOut(hdc, 5, 5, greeting, _tcslen(greeting));
EndPaint(hWnd, &ps);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
break;
}
return 0;
}
#endif
#ifdef STEP3
// Replace WinMain with InitInstanceInPCWindow so the Native Client Module can
// launch the original application. Note the inclusion of a message-handling
// loop. STEP4 will replace the loop with a callback.
HINSTANCE g_hInstance = NULL;
HWND g_hWnd = NULL;
int InitInstanceInPCWindow() {
WNDCLASSEX winClass; MSG uMsg;
memset(&uMsg,0,sizeof(uMsg));
winClass.lpszClassName = _T("MY_WINDOWS_CLASS");
winClass.cbSize = sizeof(WNDCLASSEX);
winClass.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
winClass.lpfnWndProc = WndProc;
winClass.hInstance = g_hInstance;
winClass.hIcon = NULL;
winClass.hIconSm = NULL;
winClass.hCursor = LoadCursor(NULL, IDC_ARROW);
winClass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
winClass.lpszMenuName = NULL;
winClass.cbClsExtra = 0;
winClass.cbWndExtra = 0;
if (!RegisterClassEx(&winClass))
return E_FAIL;
g_hWnd = CreateWindowEx(
0, _T("MY_WINDOWS_CLASS"),
_T("hello_nacl"), WS_OVERLAPPEDWINDOW,
0, 0, 640, 480, NULL, NULL, g_hInstance, NULL);
if (g_hWnd == NULL)
return E_FAIL;
ShowWindow(g_hWnd, 1);
UpdateWindow(g_hWnd);
#ifdef STEP4
// Skip the message loop, schedule a callback instead to periodically check
// for messages. Here we schedule at 100ms intervals.
ppb_core_interface->CallOnMainThread(100, HelloWorldCallback, 0);
return 0;
#else
// Main message loop, Windows style.
while(uMsg.message != WM_QUIT) {
if (PeekMessage(&uMsg, NULL, 0, 0, PM_REMOVE)) {
TranslateMessage( &uMsg );
DispatchMessage( &uMsg );
}
}
return uMsg.wParam;
#endif
}
#endif

There is a lot of extra code in this example, but here is the problem:
PP_EXPORT const void* PPP_GetInterface(const char* interface_name) {
if (strcmp(interface_name, PPP_INSTANCE_INTERFACE) == 0) {
static PPP_Instance instance_interface = {
&Instance_DidCreate,
&Instance_DidDestroy,
&Instance_DidChangeView,
&Instance_DidChangeFocus,
&Instance_HandleDocumentLoad,
//&HandleMessage,
};
return &instance_interface;
}
return NULL;
}
When you post a message to your module, this function is called requesting the PPP_Messaging;1.0 interface. This code is not handling that case, so it returns NULL to the caller, which then crashes.
This is not desirable behavior (it should probably produce an error instead), but it is not very surprising.
To fix this bug, you need to return an interface when PPP_MESSAGING_INTERFACE is requested:
...
} else if (strcmp(interface_name, PPP_MESSAGING_INTERFACE) == 0) {
static PPP_Messaging messaging_interface = {
&HandleMessage,
};
return &messaging_interface;
}