从生成的 child-process 通过 IPC-channel 发送错误 Object

Question

我启用了 parent 和 child 进程之间的通信以便发送 JSON 如下：

Child:

try {  
  var price1 = parseInt(process.argv[2]);
  if (!price1) {
     throw new Error('Price in calculations.js undefined');
  }
  var result = {
    'timeStamp' : Date(),
    'prices' : { 'player1' : price1, 'player2' : 666}
  };
  process.send(result);
} catch (e) {
  // In case of an error, I get here as expected.
  process.send(e);
}

Parent:

var spawn = require('child_process').spawn;
var child = spawn('node', ['calculations.js', 333],  {stdio: [null,null,'pipe','ipc']});
child.on('message', function(data) {    
  if (data instanceof Error) {
    // In case of an error, this is never reached.
  } else {
    // do sthing with JSON object.
  }
});

JSON 东西工作正常。但如果我引发错误，它就不起作用。我想将整个 error-object（带有消息和 stack-trace）从 child 发送到 parent。但它似乎不是我发送的错误实例。

Answer 1

这是我尝试过的东西，

var Error=function(mes){
    this.message=mes;
};

try {  
  var price1 = parseInt(process.argv[4]);
 if (!price1) {
     throw new Error('Price in calculations.js undefined');
 }
  var result = {
    'timeStamp' : Date(),
    'prices' : { 'player1' : price1, 'player2' : 666}
  };  console.log("inside try");
  process.send(result);
} catch (e) {
  // In case of an error, I get here as expected.
  console.log("inside catch");
  process.send(e);
}

先创建object Error再抛出，否则只会传递一个空的object而不是instanceof Error.

还有 parent

var child = require('child_process').fork(__dirname + '/SO2.js', [333],  {stdio: [null,null,'pipe','ipc']});

child.on('message', function(data) {
  if(data.timeStamp){
    console.log("result received ");
  } 
  else{
    // do sthing with JSON object.
    console.log("user defined error messege"+data.message + JSON.stringify(data));
  }
});

Answer 2

进程不共享内存，因此唯一的通信方式是使用字符串，对象在发送时 JSON 序列化并在接收时 JSON 解析回来。默认情况下，错误对象不能很好地序列化：

JSON.stringify(new Error())
"{}"

此外，JSON 已解析的对象未类型化，因此 instanceof 无法工作。

您可以为错误对象创建序列化挂钩：

Error.prototype.toJSON = function() {
    var ret = {
        name: this.name,
        message: this.message,
        stack: this.stack,
        __error__: true
    };
    // Add any custom properties such as .code in file-system errors
    Object.keys(this).forEach(function(key) {
        if (!ret[key]) {
            ret[key] = this[key];
        }
    }, this);
    return ret;
};

在方法定义错误对象序列化之后更好：

 JSON.stringify(new Error())

"{"name":"Error","message":"","stack":"Error\n    at <anonymous>:2:16\n    at Object.InjectedScript._evaluateOn (<anonymous>:762:137)\n    at Object.InjectedScript._evaluateAndWrap (<anonymous>:695:34)\n    at Object.InjectedScript.evaluate (<anonymous>:609:21)","__error__":true}"

然后自动重建：

function getMessageReceiver(fn) {
    return function(data) {
        var result = data;
        if (data && data.__error__) {
            result = new Error();
            result.message = data.message;
            result.stack = data.stack;
            result.name = data.name;
            Object.keys(data).forEach(function(key) {
                if (!result[key]) {
                    result[key] = data[key];
                }
            });
        }
        return fn.call(this, result);
    }
}

最后：

child.on('message', getMessageReceiver(function(data) {    
  if (data instanceof Error) {
    console.log(data.stack); // Stack is from child process
  } else {
    // do sthing with JSON object.
  }
}));

从生成的 child-process 通过 IPC-channel 发送错误 Object

Sending an Error Object from a spawned child-process over an IPC-channel

javascript

inter-process-communicat

node.js