nodejs的错误处理过程记录

1.  const net = require('net');  
2.  net.connect({port: 9999})

1.  events.js:170  
2.        throw er; // Unhandled 'error' event  
3.        ^  
4.    
5.  Error: connect ECONNREFUSED 127.0.0.1:9999  
6.      at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1088:14)  
7.  Emitted 'error' event at:  
8.      at emitErrorNT (internal/streams/destroy.js:91:8)  
9.      at emitErrorAndCloseNT (internal/streams/destroy.js:59:3)  
10.     at processTicksAndRejections (internal/process/task_queues.js:81:17)

1.  const req = new TCPConnectWrap();  
2.  req.oncomplete = afterConnect;  
3.  req.address = address;  
4.  req.port = port;  
5.  req.localAddress = localAddress;  
6.  req.localPort = localPort;  
7.  // 开始三次握手建立连接  
8.  err = self._handle.connect(req, address, port);

1.  err = req_wrap->Dispatch(uv_tcp_connect,  
2.                               &wrap->handle_,  
3.                               reinterpret_cast<const sockaddr*>(&addr),  
4.                               AfterConnect);

1.  do {  
2.      errno = 0;  
3.      // 非阻塞调用  
4.      r = connect(uv__stream_fd(handle), addr, addrlen);  
5.    } while (r == -1 && errno == EINTR);  
6.    // 连接错误，判断错误码  
7.    if (r == -1 && errno != 0) {  
8.      // 还在连接中，不是错误，等待连接完成，事件变成可读  
9.      if (errno == EINPROGRESS)  
10.       ; /* not an error */  
11.     else if (errno == ECONNREFUSED)  
12.       // 连接被拒绝  
13.       handle->delayed_error = UV__ERR(ECONNREFUSED);  
14.     else  
15.       return UV__ERR(errno);  
16.   }  
17.   uv__req_init(handle->loop, req, UV_CONNECT);  
18.   req->cb = cb;  
19.   req->handle = (uv_stream_t*) handle;  
20.   QUEUE_INIT(&req->queue);  
21.   // 挂载到handle，等待可写事件  
22.   handle->connect_req = req;  
23.   uv__io_start(handle->loop, &handle->io_watcher, POLLOUT);

1.  getsockopt(uv__stream_fd(stream),  
2.                 SOL_SOCKET,  
3.                 SO_ERROR,  
4.                 &error,  
5.                 &errorsize);  
6.  error = UV__ERR(error);  
7.  if (req->cb)  
8.      req->cb(req, error);

1.  Local<Value> argv[5] = {  
2.     Integer::New(env->isolate(), status),  
3.     wrap->object(),  
4.     req_wrap->object(),  
5.     Boolean::New(env->isolate(), readable),  
6.     Boolean::New(env->isolate(), writable)  
7.   };  
8.    
9.   req_wrap->MakeCallback(env->oncomplete_string(), arraysize(argv), argv);

1.  const ex = exceptionWithHostPort(status,  
2.                                   'connect',  
3.                                   req.address,  
4.                                   req.port,  
5.                                   details);  
6.  if (details) {  
7.    ex.localAddress = req.localAddress;  
8.    ex.localPort = req.localPort;  
9.  }  
10. // 销毁socket  
11. self.destroy(ex);

1.  function uvExceptionWithHostPort(err, syscall, address, port) {  
2.    const [ code, uvmsg ] = uvErrmapGet(err) || uvUnmappedError;  
3.    const message = `${syscall} $[code]: ${uvmsg}`;  
4.    let details = '';  
5.    
6.    if (port && port > 0) {  
7.      details = ` ${address}:${port}`;  
8.    } else if (address) {  
9.      details = ` ${address}`;  
10.   }  
11.   const tmpLimit = Error.stackTraceLimit;  
12.   Error.stackTraceLimit = 0;  
13.   const ex = new Error(`${message}${details}`);  
14.   Error.stackTraceLimit = tmpLimit;  
15.   ex.code = code;  
16.   ex.errno = err;  
17.   ex.syscall = syscall;  
18.   ex.address = address;  
19.   if (port) {  
20.     ex.port = port;  
21.   }  
22.   // 获取调用栈信息但不包括当前调用的函数uvExceptionWithHostPort，注入stack字段到ex中  
23.   Error.captureStackTrace(ex, excludedStackFn || uvExceptionWithHostPort);  
24.   return ex;  
25. }

1.  function uvErrmapGet(name) {  
2.    uvBinding = lazyUv();  
3.    if (!uvBinding.errmap) {  
4.      uvBinding.errmap = uvBinding.getErrorMap();  
5.    }  
6.    return uvBinding.errmap.get(name);  
7.  }  
8.    
9.  function lazyUv() {  
10.   if (!uvBinding) {  
11.     uvBinding = internalBinding('uv');  
12.   }  
13.   return uvBinding;  
14. }

1.  void GetErrMap(const FunctionCallbackInfo<Value>& args) {  
2.    Environment* env = Environment::GetCurrent(args);  
3.    Isolate* isolate = env->isolate();  
4.    Local<Context> context = env->context();  
5.    
6.    Local<Map> err_map = Map::New(isolate);  
7.    // 从per_process::uv_errors_map中获取错误信息  
8.    size_t errors_len = arraysize(per_process::uv_errors_map);  
9.    // 赋值  
10.   for (size_t i = 0; i < errors_len;   i) {  
11.      // map的键是 uv_errors_map每个元素中的value，值是name和message
12.     const auto& error = per_process::uv_errors_map[i];  
13.     Local<Value> arr[] = {OneByteString(isolate, error.name),  
14.                           OneByteString(isolate, error.message)}; 
15.     if (err_map  
16.             ->Set(context,  
17.                   Integer::New(isolate, error.value),  
18.                   Array::New(isolate, arr, arraysize(arr)))  
19.             .IsEmpty()) {  
20.       return;  
21.     }  
22.   }  
23.   
24.   args.GetReturnValue().Set(err_map);  
25. }

1.  struct UVError {
2.    int value;
3.    const char* name;
4.    const char* message;
5.  };
6.  
7.  static const struct UVError uv_errors_map[] = {  
8.  #define V(name, message) {UV_##name, #name, message},  
9.      UV_ERRNO_MAP(V)  
10. #undef V  
11. };

1.  {UV_E2BIG, "E2BIG", "argument list too long"},  
2.  {UV_EACCES, "EACCES", "permission denied"},  
3.  {UV_EADDRINUSE, "EADDRINUSE", "address already in use"},  
4.  ……

1.  {  
2.    // 键是一个数字，由Libuv定义，其实是封装了操作系统的定义
3.    UV_ECONNREFUSED: ["ECONNREFUSED", "connection refused"],    
4.    UV_ECONNRESET: ["ECONNRESET", "connection reset by peer"]   
5.    ...   
6.  }

1.  static void tcp_reset(struct sock *sk)  
2.  {  
3.      switch (sk->sk_state) {  
4.          case TCP_SYN_SENT:  
5.              sk->sk_err = ECONNREFUSED;  
6.              break;  
7.           // ...
8.      }  
9.    
10. }