Node.JS

十个Node.js开发易犯错误之六:很少用日志

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　许多Node入门教程只是展示小的案例，里面使用了console.log，这给大家误以为这是一种日志实现方式。

　你应该使用比console.log更好的日志，下面是原因：

  • 没有必要为大型复杂对象使用 util.inspect;
  • 内建序列化器如错误 请求和响应对象;
  • 支持多个日志输出源控制;
  • 自动包含主机名称, 流程id, 应用名称;
  • 支持日志的多级别 (debug, info, error, fatal etc);
  • 高级功能如日志文件的rotation等(每隔一段时间重新生成新日志，就日志打包压缩存储)
　

　你可以从bunyan得到这些产品基本的日志模块。在其之上你也可以得到方便的CLI 部署工具。让我们看看这些案例如何使用：

var http = require('http');

var bunyan = require('bunyan');

 

var log = bunyan.createLogger({

  name: 'myserver',

  serializers: {

    req: bunyan.stdSerializers.req,

    res: bunyan.stdSerializers.res

  }

});

var server = http.createServer(function (req, res) {

  log.info({ req: req }, 'start request');  // <-- this is the guy we're testing

  res.writeHead(200, { 'Content-Type': 'text/plain' });

  res.end('Hello World\n');

  log.info({ res: res }, 'done response');  // <-- this is the guy we're testing

});

 

　注意代码中日志写法，完整代码见Github

　如果运行这段代码，我们会得到如下结果：

$ node server.js

{"name":"myserver","hostname":"MBP.local","pid":14304,"level":30,"msg":"server listening","time":"2014-11-16T11:30:13.263Z","v":0}
{"name":"myserver","hostname":"MBP.local","pid":14304,"level":30,"req":{"method":"GET","url":"/path?q=1#anchor","headers":{"x-hi":"Mom","host":"127.0.0.1:1337","connection":"keep-alive"},"
remoteAddress":"127.0.0.1","remotePort":61580},"msg":"start request","time":"2014-11-16T11:30:13.271Z","v":0} {"name":"myserver","hostname":"MBP.local","pid":14304,"level":30,"res":{"statusCode":200,"header":"HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\nDate: Sun, 16 Nov 2014 11:30:13 GMT\r\nConnection: keep-alive\r\nTransfer-Encoding: chunked\r\n\r\n"},"msg":"done response","time":"2014-11-16T11:30:13.273Z","v":0}

　在开发环境，最好使用CLI工具，如下图：


　正如你看到，bunyan给你许多当前流程的有用信息，这些对于生产环境很重要，另外一个方便特性是你能将日志管道输出到一个或多个流。

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