Node.js 源码剖析
调试、诊断子线程最直接的方式就是像调试、诊断主线程一样，但是无论是动态开启还是静态开启，子线程都不可避免地需要内置一些相关的非业务代码，本文介绍另外一种对子线程代码无侵入的调试方式，另外也介绍一下通过子线程调试主线程的方式。
1 初始化子线程的Inspector
在Node.js启动子线程的时候，会初始化Inspector。
env_->InitializeInspector(std::move(inspector_parent_handle_));在分析InitializeInspector之前，我们先看一下inspector_parenthandle。
std::unique_ptr<inspector::ParentInspectorHandle> inspector_parent_handle_;inspector_parent_handle_是一个ParentInspectorHandle对象，这个对象是子线程和主线程通信的桥梁。我们看一下他的初始化逻辑（在主线程里执行）。
inspector_parent_handle_ = env->inspector_agent()->GetParentHandle(thread_id_, url);调用agent的GetParentHandle获取一个ParentInspectorHandle对象。
std::unique_ptr<ParentInspectorHandle> Agent::GetParentHandle(int thread_id, const std::string& url) {
return client_->getWorkerManager()->NewParentHandle(thread_id, url);
}内部其实是通过client_->getWorkerManager()对象的NewParentHandle方法获取ParentInspectorHandle对象，接下来我们看一下WorkerManager的NewParentHandle。
std::unique_ptr<ParentInspectorHandle> WorkerManager::NewParentHandle(int thread_id, const std::string& url) {
bool wait = !delegates_waiting_on_start_.empty();
return std::make_unique<ParentInspectorHandle>(thread_id, url, thread_, wait);
}
ParentInspectorHandle::ParentInspectorHandle(
int id, const std::string& url,
std::shared_ptr<MainThreadHandle> parent_thread,
bool wait_for_connect
)
: id_(id),
url_(url),
parent_thread_(parent_thread),
wait_(wait_for_connect) {}最终的架构图如下入所示。
int Environment::InitializeInspector(
std::unique_ptr<inspector::ParentInspectorHandle> parent_handle) {
std::string inspector_path;
inspector_path = parent_handle->url();
inspector_agent_->SetParentHandle(std::move(parent_handle));
inspector_agent_->Start(inspector_path,
options_->debug_options(),
inspector_host_port(),
is_main_thread());
}首先把ParentInspectorHandle对象保存到agent中，然后调用agent的Start方法。
bool Agent::Start(...) {
// 新建client对象
client_ = std::make_shared<NodeInspectorClient>(parent_env_, is_main);
// 调用agent中保存的ParentInspectorHandle对象的WorkerStarted
parent_handle_->WorkerStarted(client_->getThreadHandle(), ...);
}Agent::Start创建了一个client对象，然后调用ParentInspectorHandle对象的WorkerStarted方法（刚才SetParentHandle的时候保存的），我们看一下这时候的架构图。
void ParentInspectorHandle::WorkerStarted(
std::shared_ptr<MainThreadHandle> worker_thread, bool waiting) {
std::unique_ptr<Request> request(
new WorkerStartedRequest(id_, url_, worker_thread, waiting));
parent_thread_->Post(std::move(request));
}WorkerStarted创建了一个WorkerStartedRequest请求，然后通过parentthread->Post提交，parent_thread_是MainThreadInterface对象。
void MainThreadInterface::Post(std::unique_ptr<Request> request) {
Mutex::ScopedLock scoped_lock(requests_lock_);
// 之前是空则需要唤醒消费者
bool needs_notify = requests_.empty();
// 消息入队
requests_.push_back(std::move(request));
if (needs_notify) {
// 获取当前对象的一个弱引用
std::weak_ptr<MainThreadInterface>* interface_ptr = new std::weak_ptr<MainThreadInterface>(shared_from_this());
// 请求V8执行RequestInterrupt入参对应的回调
isolate_->RequestInterrupt([](v8::Isolate* isolate, void* opaque) {
// 把执行时传入的参数转成MainThreadInterface
std::unique_ptr<std::weak_ptr<MainThreadInterface>> interface_ptr {
static_cast<std::weak_ptr<MainThreadInterface>*>(opaque)
};
// 判断对象是否还有效，是则调用DispatchMessages
if (auto iface = interface_ptr->lock()) iface->DispatchMessages();
}, static_cast<void*>(interface_ptr));
}
// 唤醒消费者
incoming_message_cond_.Broadcast(scoped_lock);
}我们看看这时候的架构图。
void MainThreadInterface::DispatchMessages() {
// 遍历请求队列
requests_.swap(dispatching_message_queue_);
while (!dispatching_message_queue_.empty()) {
MessageQueue::value_type task;
std::swap(dispatching_message_queue_.front(), task);
dispatching_message_queue_.pop_front();
// 执行任务函数
task->Call(this);
}
}task是WorkerStartedRequest对象，看一下Call方法的代码。
void Call(MainThreadInterface* thread) override {
auto manager = thread->inspector_agent()->GetWorkerManager();
manager->WorkerStarted(id_, info_, waiting_);
}接着调用agent的WorkerManager的WorkerStarted。
void WorkerManager::WorkerStarted(int session_id,
const WorkerInfo& info,
bool waiting) {
children_.emplace(session_id, info);
for (const auto& delegate : delegates_) {
Report(delegate.second, info, waiting);
}
}WorkerStarted记录了一个id和上下文，因为delegates_初始化的时候是空的，所以不会执行。至此，子线程Inspector初始化的逻辑就分析完了，结构图如下。
2 主线程开启调试子线程的能力
我们可以以以下方式开启对子线程的调试。
const { Worker, workerData } = require('worker_threads');
const { Session } = require('inspector');
// 新建一个新的通信通道
const session = new Session();
session.connect();
// 创建子线程
const worker = new Worker('./httpServer.js', {workerData: {port: 80}});
// 子线程启动成功后开启调试子线程的能力
worker.on('online', () => {
session.post("NodeWorker.enable",
{waitForDebuggerOnStart: false},
(err) => {
err && console.log("NodeWorker.enable", err);
});
});
// 防止主线程退出
setInterval(() => {}, 100000);我们先来分析一下connect函数的逻辑。
connect() {
this[connectionSymbol] = new Connection((message) => this[onMessageSymbol](message));
}新建了一个Connection对象并传入一个回调函数，该回调函数在收到消息时被回调。Connection是C++层导出的对象，由模版类JSBindingsConnection实现。
template <typename ConnectionType>
class JSBindingsConnection {}我们看看导出的路逻辑。
JSBindingsConnection<Connection>::Bind(env, target);接着看Bind。
static void Bind(Environment* env, Local<Object> target) {
// class_name是Connection
Local<String> class_name = ConnectionType::GetClassName(env);
Local<FunctionTemplate> tmpl = env->NewFunctionTemplate(JSBindingsConnection::New);
tmpl->InstanceTemplate()->SetInternalFieldCount(1);
tmpl->SetClassName(class_name);
tmpl->Inherit(AsyncWrap::GetConstructorTemplate(env));
env->SetProtoMethod(tmpl, "dispatch", JSBindingsConnection::Dispatch);
env->SetProtoMethod(tmpl, "disconnect", JSBindingsConnection::Disconnect);
target->Set(env->context(),
class_name,
tmpl->GetFunction(env->context()).ToLocalChecked())
.ToChecked();
}当我们在JS层执行new Connection的时候，就会执行JSBindingsConnection::New。
static void New(const FunctionCallbackInfo<Value>& info) {
Environment* env = Environment::GetCurrent(info);
Local<Function> callback = info[0].As<Function>();
new JSBindingsConnection(env, info.This(), callback);
}我们看看新建一个JSBindingsConnection对象时的逻辑。
JSBindingsConnection(Environment* env,
Local<Object> wrap,
Local<Function> callback)
: AsyncWrap(env, wrap, PROVIDER_INSPECTORJSBINDING),
callback_(env->isolate(), callback) {
Agent* inspector = env->inspector_agent();
session_ = LocalConnection::Connect(
inspector, std::make_unique<JSBindingsSessionDelegate>(env, this)
);
}
static std::unique_ptr<InspectorSession> Connect(
Agent* inspector,
std::unique_ptr<InspectorSessionDelegate> delegate
) {
return inspector->Connect(std::move(delegate), false);
}最终是传入了一个JSBindingsSessionDelegate对象调用Agent的Connect方法。
std::unique_ptr<InspectorSession> Agent::Connect(
std::unique_ptr<InspectorSessionDelegate> delegate,
bool prevent_shutdown) {
int session_id = client_->connectFrontend(std::move(delegate),
prevent_shutdown);
// JSBindingsConnection对象的session_字段指向的对象
return std::unique_ptr<InspectorSession>(
new SameThreadInspectorSession(session_id, client_)
);
}Agent的Connect方法继续调用client_->connectFrontend。
int connectFrontend(std::unique_ptr<InspectorSessionDelegate> delegate,
bool prevent_shutdown) {
int session_id = next_session_id_++;
channels_[session_id] = std::make_unique<ChannelImpl>(env_,
client_,
getWorkerManager(),
std::move(delegate),
getThreadHandle(),
prevent_shutdown);
return session_id;
}connectFrontend新建了一个ChannelImpl对象，在新建ChannelImpl时，会初始化子线程处理的逻辑。
explicit ChannelImpl(Environment* env,
const std::unique_ptr<V8Inspector>& inspector,
std::shared_ptr<WorkerManager> worker_manager,
std::unique_ptr<InspectorSessionDelegate> delegate,
std::shared_ptr<MainThreadHandle> main_thread_,
bool prevent_shutdown)
: delegate_(std::move(delegate)), prevent_shutdown_(prevent_shutdown),
retaining_context_(false) {
session_ = inspector->connect(CONTEXT_GROUP_ID, this, StringView());
// Node.js拓展命令的处理分发器
node_dispatcher_ = std::make_unique<protocol::UberDispatcher>(this);
// trace相关
tracing_agent_ = std::make_unique<protocol::TracingAgent>(env, main_thread_);
tracing_agent_->Wire(node_dispatcher_.get());
// 处理子线程相关
if (worker_manager) {
worker_agent_ = std::make_unique<protocol::WorkerAgent>(worker_manager);
worker_agent_->Wire(node_dispatcher_.get());
}
// 处理runtime
runtime_agent_ = std::make_unique<protocol::RuntimeAgent>();
runtime_agent_->Wire(node_dispatcher_.get());
}我们这里只关注处理子线程相关的逻辑。看一下 workeragent->Wire。
void WorkerAgent::Wire(UberDispatcher* dispatcher) {
frontend_.reset(new NodeWorker::Frontend(dispatcher->channel()));
NodeWorker::Dispatcher::wire(dispatcher, this);
auto manager = manager_.lock();
workers_ = std::make_shared<NodeWorkers>(frontend_, manager->MainThread());
}这时候的架构图如下
void Dispatcher::wire(UberDispatcher* uber, Backend* backend)
{
std::unique_ptr<DispatcherImpl> dispatcher(new DispatcherImpl(uber->channel(), backend));
uber->setupRedirects(dispatcher->redirects());
uber->registerBackend("NodeWorker", std::move(dispatcher));
}首先新建了一个DispatcherImpl对象。
DispatcherImpl(FrontendChannel* frontendChannel, Backend* backend)
: DispatcherBase(frontendChannel)
, m_backend(backend) {
m_dispatchMap["NodeWorker.sendMessageToWorker"] = &DispatcherImpl::sendMessageToWorker;
m_dispatchMap["NodeWorker.enable"] = &DispatcherImpl::enable;
m_dispatchMap["NodeWorker.disable"] = &DispatcherImpl::disable;
m_dispatchMap["NodeWorker.detach"] = &DispatcherImpl::detach;
}除了初始化一些字段，另外了一个kv数据结构，这个是一个路由配置，后面我们会看到它的作用。新建完DispatcherImpl后又调用了uber->registerBackend("NodeWorker", std::move(dispatcher))注册该对象。
void UberDispatcher::registerBackend(const String& name, std::unique_ptr<protocol::DispatcherBase> dispatcher)
{
m_dispatchers[name] = std::move(dispatcher);
}这时候的架构图如下。
post(method, params, callback) {
// 忽略参数处理
// 保存请求对应的回调
if (callback) {
this[messageCallbacksSymbol].set(id, callback);
}
// 调用C++的dispatch
this[connectionSymbol].dispatch(JSONStringify(message));
}this[connectionSymbol]对应的是JSBindingsConnection对象。
static void Dispatch(const FunctionCallbackInfo<Value>& info) {
Environment* env = Environment::GetCurrent(info);
JSBindingsConnection* session;
ASSIGN_OR_RETURN_UNWRAP(&session, info.Holder());
if (session->session_) {
session->session_->Dispatch(
ToProtocolString(env->isolate(), info[0])->string());
}
}session_是一个SameThreadInspectorSession对象。
void SameThreadInspectorSession::Dispatch(
const v8_inspector::StringView& message) {
auto client = client_.lock();
client->dispatchMessageFromFrontend(session_id_, message);
}
void dispatchMessageFromFrontend(int session_id, const StringView& message) {
channels_[session_id]->dispatchProtocolMessage(message);
}最终调用了ChannelImpl的dispatchProtocolMessage。
void dispatchProtocolMessage(const StringView& message) {
std::string raw_message = protocol::StringUtil::StringViewToUtf8(message);
std::unique_ptr<protocol::DictionaryValue> value =
protocol::DictionaryValue::cast(protocol::StringUtil::parseMessage(
raw_message, false));
int call_id;
std::string method;
// 解析命令
node_dispatcher_->parseCommand(value.get(), &call_id, &method);
// 判断命令是V8内置命令还是Node.js拓展的命令
if (v8_inspector::V8InspectorSession::canDispatchMethod(
Utf8ToStringView(method)->string())) {
session_->dispatchProtocolMessage(message);
} else {
node_dispatcher_->dispatch(call_id, method, std::move(value),
raw_message);
}
}因为NodeWorker.enable是Node.js拓展的命令，所以会走到else里面的逻辑。根据路由配置找到该命令对应的处理逻辑（NodeWorker.enable以.切分，对应两级路由）。
void UberDispatcher::dispatch(int callId, const String& in_method, std::unique_ptr<Value> parsedMessage, const ProtocolMessage& rawMessage)
{
// 找到一级路由配置
protocol::DispatcherBase* dispatcher = findDispatcher(method);
std::unique_ptr<protocol::DictionaryValue> messageObject = DictionaryValue::cast(std::move(parsedMessage));
// 交给一级路由处理器处理
dispatcher->dispatch(callId, method, rawMessage, std::move(messageObject));
}NodeWorker.enable对应的路由处理器代码如下
void DispatcherImpl::dispatch(int callId, const String& method, const ProtocolMessage& message, std::unique_ptr<protocol::DictionaryValue> messageObject)
{
// 查找二级路由
std::unordered_map<String, CallHandler>::iterator it = m_dispatchMap.find(method);
protocol::ErrorSupport errors;
// 找到处理函数
(this->*(it->second))(callId, method, message, std::move(messageObject), &errors);
}dispatch继续寻找命令对应的处理函数，最终找到NodeWorker.enable命令的处理函数为DispatcherImpl::enable。
void DispatcherImpl::enable(...)
{
std::unique_ptr<DispatcherBase::WeakPtr> weak = weakPtr();
DispatchResponse response = m_backend->enable(...);
// 返回响应给命令（类似请求/响应模式）
weak->get()->sendResponse(callId, response);
}根据架构图可以知道m_backend是WorkerAgent对象。
DispatchResponse WorkerAgent::enable(bool waitForDebuggerOnStart) {
auto manager = manager_.lock();
std::unique_ptr<AgentWorkerInspectorDelegate> delegate(new AgentWorkerInspectorDelegate(workers_));
event_handle_ = manager->SetAutoAttach(std::move(delegate));
return DispatchResponse::OK();
}继续调用WorkerManager的SetAutoAttach方法。
std::unique_ptr<WorkerManagerEventHandle> WorkerManager::SetAutoAttach(
std::unique_ptr<WorkerDelegate> attach_delegate) {
int id = ++next_delegate_id_;
// 保存delegate
delegates_[id] = std::move(attach_delegate);
const auto& delegate = delegates_[id];
// 通知子线程
for (const auto& worker : children_) {
Report(delegate, worker.second, false);
}
...
}SetAutoAttach遍历子线程。
void Report(const std::unique_ptr<WorkerDelegate>& delegate,
const WorkerInfo& info, bool waiting) {
if (info.worker_thread)
delegate->WorkerCreated(info.title, info.url, waiting, info.worker_thread);
}info是一个WorkerInfo对象，该对象是子线程初始化和主线程建立关系的数据结构。delegate是AgentWorkerInspectorDelegate对象。
void WorkerCreated(const std::string& title,
const std::string& url,
bool waiting,
std::shared_ptr<MainThreadHandle> target) override {
workers_->WorkerCreated(title, url, waiting, target);
}workers_是一个NodeWorkers对象。
void NodeWorkers::WorkerCreated(const std::string& title,
const std::string& url,
bool waiting,
std::shared_ptr<MainThreadHandle> target) {
auto frontend = frontend_.lock();
std::string id = std::to_string(++next_target_id_);
// 处理数据通信的delegate
auto delegate = thread_->MakeDelegateThreadSafe(
std::unique_ptr<InspectorSessionDelegate>(
new ParentInspectorSessionDelegate(id, shared_from_this())
)
);
// 建立和子线程V8 Inspector的通信通道
sessions_[id] = target->Connect(std::move(delegate), true);
frontend->attachedToWorker(id, WorkerInfo(id, title, url), waiting);
}WorkerCreated建立了一条和子线程通信的通道，然后通知命令的发送方通道建立成功。这时候架构图如下。
void Frontend::attachedToWorker(const String& sessionId, std::unique_ptr<protocol::NodeWorker::WorkerInfo> workerInfo, bool waitingForDebugger)
{
std::unique_ptr<AttachedToWorkerNotification> messageData = AttachedToWorkerNotification::create()
.setSessionId(sessionId)
.setWorkerInfo(std::move(workerInfo))
.setWaitingForDebugger(waitingForDebugger)
.build();
// 触发NodeWorker.attachedToWorker
m_frontendChannel->sendProtocolNotification(InternalResponse::createNotification("NodeWorker.attachedToWorker", std::move(messageData)));
}继续看sendProtocolNotification
void sendProtocolNotification(
std::unique_ptr<Serializable> message) override {
sendMessageToFrontend(message->serializeToJSON());
}
void sendMessageToFrontend(const StringView& message) {
delegate_->SendMessageToFrontend(message);
}这里的delegate_是一个JSBindingsSessionDelegate对象。
void SendMessageToFrontend(const v8_inspector::StringView& message)
override {
Isolate* isolate = env_->isolate();
HandleScope handle_scope(isolate);
Context::Scope context_scope(env_->context());
MaybeLocal<String> v8string = String::NewFromTwoByte(isolate,
message.characters16(),
NewStringType::kNormal, message.length()
);
Local<Value> argument = v8string.ToLocalChecked().As<Value>();
// 收到消息执行回调
connection_->OnMessage(argument);
}
// 执行JS层回调
void OnMessage(Local<Value> value) {
MakeCallback(callback_.Get(env()->isolate()), 1, &value);
}JS层回调逻辑如下。
[onMessageSymbol](message) {
const parsed = JSONParse(message);
// 收到的消息如果是某个请求的响应，则有个id字段记录了请求对应的id，否则则触发事件
if (parsed.id) {
const callback = this[messageCallbacksSymbol].get(parsed.id);
this[messageCallbacksSymbol].delete(parsed.id);
if (callback) {
callback(null, parsed.result);
}
} else {
this.emit(parsed.method, parsed);
this.emit('inspectorNotification', parsed);
}
}主线程拿到Worker Session对一个的id，后续就可以通过命令NodeWorker.sendMessageToWorker加上该id和子线程通信。大致原理如下，主线程通过自己的channel和子线程的channel进行通信，从而达到控制子线程的目的。
void DispatcherImpl::sendMessageToWorker(...)
{
std::unique_ptr<DispatcherBase::WeakPtr> weak = weakPtr();
DispatchResponse response = m_backend->sendMessageToWorker(in_message, in_sessionId);
// 响应
weak->get()->sendResponse(callId, response);
return;
}
继续分析m_backend->sendMessageToWorker。
DispatchResponse WorkerAgent::sendMessageToWorker(const String& message,
const String& sessionId) {
workers_->Receive(sessionId, message);
return DispatchResponse::OK();
}
void NodeWorkers::Receive(const std::string& id, const std::string& message) {
auto it = sessions_.find(id);
it->second->Dispatch(Utf8ToStringView(message)->string());
}sessions_对应的是和子线程的通信的数据结构CrossThreadInspectorSession。看一下该对象的Dispatch方法。
void Dispatch(const StringView& message) override {
state_.Call(&MainThreadSessionState::Dispatch,
StringBuffer::create(message));
}再次调了MainThreadSessionState::Dispatch
void Dispatch(std::unique_ptr<StringBuffer> message) {
session_->Dispatch(message->string());
}session_是SameThreadInspectorSession对象。继续看它的Dispatch方法。
void SameThreadInspectorSession::Dispatch(
const v8_inspector::StringView& message) {
auto client = client_.lock();
client->dispatchMessageFromFrontend(session_id_, message);
}
void dispatchMessageFromFrontend(int session_id, const StringView& message) {
channels_[session_id]->dispatchProtocolMessage(message);
}通过层层调用，最终拿到了一个合子线程通信的channel，dispatchProtocolMessage方法刚才已经分析过，该方法会根据命令做不同的处理，因为我们这里发送的是V8内置的命令，所以会交给V8 Inspector处理。当V8 Inspector处理完后，会通过ChannelImpl的sendResponse返回结果。
void sendResponse(
int callId,
std::unique_ptr<v8_inspector::StringBuffer> message) override {
sendMessageToFrontend(message->string());
}
void sendMessageToFrontend(const StringView& message) {
delegate_->SendMessageToFrontend(message);
}这里的delegate_是ParentInspectorSessionDelegate对象。
void SendMessageToFrontend(const v8_inspector::StringView& msg) override {
std::string message = protocol::StringUtil::StringViewToUtf8(msg);
workers_->Send(id_, message);
}
void NodeWorkers::Send(const std::string& id, const std::string& message) {
auto frontend = frontend_.lock();
if (frontend)
frontend->receivedMessageFromWorker(id, message);
}
void Frontend::receivedMessageFromWorker(const String& sessionId, const String& message)
{
std::unique_ptr<ReceivedMessageFromWorkerNotification> messageData = ReceivedMessageFromWorkerNotification::create()
.setSessionId(sessionId)
.setMessage(message)
.build();
// 触发NodeWorker.receivedMessageFromWorker
m_frontendChannel->sendProtocolNotification(InternalResponse::createNotification("NodeWorker.receivedMessageFromWorker", std::move(messageData)));
}m_frontendChannel是主线程的ChannelImpl对象。
void sendProtocolNotification(
std::unique_ptr<Serializable> message) override {
sendMessageToFrontend(message->serializeToJSON());
}
void sendMessageToFrontend(const StringView& message) {
delegate_->SendMessageToFrontend(message);
}delegate_是C++层传入的JSBindingsSessionDelegate对象。最终通过JSBindingsSessionDelegate对象回调JS层，之前已经分析过就不再赘述。至此，主线程就具备了控制子线程的能力，但是控制方式有很多种。
2.1 使用通用的V8命令
通过下面代码收集子线程的CPU Profile信息。
const { Worker, workerData } = require('worker_threads');
const { Session } = require('inspector');
const session = new Session();
session.connect();
let id = 1;
function post(sessionId, method, params, callback) {
session.post('NodeWorker.sendMessageToWorker', {
sessionId,
message: JSON.stringify({ id: id++, method, params })
}, callback);
}
session.on('NodeWorker.attachedToWorker', (data) => {
post(data.params.sessionId, 'Profiler.enable');
post(data.params.sessionId, 'Profiler.start');
// 收集一段时间后提交停止收集命令
setTimeout(() => {
post(data.params.sessionId, 'Profiler.stop');
}, 10000)
});
session.on('NodeWorker.receivedMessageFromWorker', ({ params: { message }}) => {
const data = JSON.parse(message);
console.log(data);
});
const worker = new Worker('./httpServer.js', {workerData: {port: 80}});
worker.on('online', () => {
session.post("NodeWorker.enable",{waitForDebuggerOnStart: false}, (err) => { console.log(err, "NodeWorker.enable");});
});
setInterval(() => {}, 100000);通过这种方式可以通过命令控制子线程的调试和数据收集。
2.2 在子线程中动态执行脚本
可以通过执行脚本开启子线程的WebSocket服务，像调试主线程一样。
const { Worker, workerData } = require('worker_threads');
const { Session } = require('inspector');
const session = new Session();
session.connect();
let workerSessionId;
let id = 1;
function post(method, params) {
session.post('NodeWorker.sendMessageToWorker', {
sessionId: workerSessionId,
message: JSON.stringify({ id: id++, method, params })
});
}
session.on('NodeWorker.receivedMessageFromWorker', ({ params: { message }}) => {
const data = JSON.parse(message);
console.log(data);
});
session.on('NodeWorker.attachedToWorker', (data) => {
workerSessionId = data.params.sessionId;
post("Runtime.evaluate", {
includeCommandLineAPI: true,
expression: `const inspector = process.binding('inspector');
inspector.open();
inspector.url();
`
}
);
});
const worker = new Worker('./httpServer.js', {workerData: {port: 80}});
worker.on('online', () => {
session.post("NodeWorker.enable",{waitForDebuggerOnStart: false}, (err) => { err && console.log("NodeWorker.enable", err);});
});
setInterval(() => {}, 100000);执行上面的代码就拿到以下输出
{
id: 1,
result: {
result: {
type: 'string',
value: 'ws://127.0.0.1:9229/c0ca16c8-55aa-4651-9776-fca1b27fc718'
}
}
}通过该地址，客户端就可以对子线程进行调试了。上面代码里使用process.binding而不是require加载inspector，因为刚才通过NodeWorker.enable命令为子线程创建了一个到子线程Inspector的channel，而JS模块里判断如果channel非空则报错Inspector已经打开。所以这里需要绕过这个限制，直接加载C++模块开启WebSocket服务器。
3 子线程调试主线程
不仅可以通过主线程调试子线程，还可以通过子线程调试主线程。Node.js在子线程暴露了connectToMainThread方法连接到主线程的Inspector（只能在work_threads中使用），实现的原理和之前分析的类似，主要是子线程连接到主线程的V8 Inspector，通过和该Inspector完成对主线程的控制。看下面一个例子。 主线程代码
const { Worker, workerData } = require('worker_threads');
const http = require('http');
const worker = new Worker('./worker.js', {workerData: {port: 80}});
http.createServer((_, res) => {
res.end('main');
}).listen(8000);worker.js代码如下
const fs = require('fs');
const { workerData: { port } } = require('worker_threads');
const { Session } = require('inspector');
const session = new Session();
session.connectToMainThread();
session.post('Profiler.enable');
session.post('Profiler.start');
setTimeout(() => {
session.post('Profiler.stop', (err, data) => {
if (data.profile) {
fs.writeFileSync('./profile.cpuprofile', JSON.stringify(data.profile));
}
});
}, 5000)