xlog

Simple express/connect middleware that extends console.log and console.err to add a prefix which contains the node.js PID and the http request URL and an identification counter.

The node implementation at Yahoo uses cluster that spawns multiple processes that handle internet traffic. There are some situation when errors are logged but it is not clear what caused it, this is specially true of uncaught exceptions. This module captures the most common async functions available in node so it can capture the request and display the information in the error log.

Both the console.log and console.error are extended to display the PID of the process that generated the log as well as the request method and URL path. This information is only displayed the first time a log is generated for a request when it is indexed. Subsequent logs will only show the PID and the index.

For example is there are two entry points ('/getUser' and '/setUser') with GET and POST methods the log file could look something like:

[1234:1] Method: GET - url: /getUser 
[1234:1] GetMessage1`
[1234:2] Method: POST - url: /setUser
[1234:2] PostMessage1
[1234:1] GetMessage2
[1333:3] Method: GET - url: /getUser
[1333:3] GetMessage2User</br>
[1333:3] GetMessage2</br>

The exception to the indexing rule is uncaught exceptions when the module will always display the PID and request information.

install

With npm do:

npm install xlog

usage

var express = require('express'),
    xlog = require('xlog');

var app = express();

app.use(xlog());

app.listen(8000);