node.js middleware to write raw request body to log file.

gistfile1.js

var fs = require('fs');

app.use(function(req, res, next) {
    req.rawBody = '';
    req.setEncoding('utf8');

    req.on('data', function(chunk) {
        req.rawBody += chunk;
    });

    req.on('end', function() {
        fs.writeFile('request-body.log', req.rawBody, function (err) {
            console.log(err);
        });

        next();
    });
});