Tutorial 3: Express

Express is a popular web application framework for node. The E2E Transaction Logger provides a middleware for express. This tutorial shows how to use the E2E Transaction Logger with express to achieve the same result as in tutorial 2.

Creating the Server

Create the server using express. The DB and SAP functions are the same as in the tutorial 2 project.

JS

var express = require('express');
var fs = require('fs');

function sapGetCustomer(id, cb){
    ...
}
function dbGetCustomerDetail(customer, cb){
    ...
}
var app = express();
app.get('/hello',function(req, res){
    fs.readFile(__dirname + '/Hello.html',function(err, data){
        res.writeHead(200, {'Content-Type': 'text/html'});
        res.end(data);
    });
});
app.get('/goodbye', function(req, res){
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Good Bye\n');
});
app.get('/do-something', function(req, res){
    sapGetCustomer(1, function(err, customer){
        if(err){
            res.writeHead(500, {'Content-Type': 'application/json'});
            res.end(JSON.stringify(err));
            return;
        }
        dbGetCustomerDetail(customer, function(err, customerWithDetail){
            if(err){
                res.writeHead(200, {'Content-Type': 'application/json'});
                res.end(JSON.stringify(customer));
                return;
            }
            res.writeHead(200, {'Content-Type': 'application/json'});
            res.end(JSON.stringify(customerWithDetail));
        });
    });
});
app.listen(1337, function() {
    console.log('Server running at http://127.0.0.1:1337/');
});

Now the server is doing the same as in tutorial 2 except for logging.

Adding the Logging

Now, add the logging.

Transactions

To log all transactions made by an express application, you can simply use the E2E Transaction Logger middleware.

JS

var e2eLogger = require('e2e-transaction-logger');

var app = express();
app.use(e2eLogger.transactionLoggerMiddleware());

Then you will get logs like these:

BASH

2014-04-30    13:01:39    +0200    9cf8bc91-0b82-4ce9-a592-423bd774bdad    1    GET /hello    0    OK    INTERFACE    SERVICE_ENTER        
2014-04-30    13:01:39    +0200    9cf8bc91-0b82-4ce9-a592-423bd774bdad    1    GET /hello    6    OK    INTERFACE    SERVICE_EXIT        
2014-04-30    13:01:55    +0200    1cfd87b5-aa95-41ea-b15e-560a3290b5a1    2    GET /do-something    0    OK    INTERFACE    SERVICE_ENTER        
2014-04-30    13:01:57    +0200    1cfd87b5-aa95-41ea-b15e-560a3290b5a1    2    GET /do-something    1856    OK    INTERFACE    SERVICE_EXIT        
2014-04-30    13:02:03    +0200    ac650a93-facc-4e5a-846c-6aae9201fd2a    3    GET /goodbye    0    OK    INTERFACE    SERVICE_ENTER        
2014-04-30    13:02:03    +0200    ac650a93-facc-4e5a-846c-6aae9201fd2a    3    GET /goodbye    1    OK    INTERFACE    SERVICE_EXIT

The state of the transaction is defined by the status code of the response: failed if >= 400.

IOs

The transaction logger middleware adds the trx attribute in the request object. You can use it to log the IO calls.

JS

app.get('/hello',function(req, res){
    var io = req.trx.startIO('Read','FILE','Hello.html');
    fs.readFile(__dirname + '/Hello.html',function(err, data){
        io.end('OK');
        res.writeHead(200, {'Content-Type': 'text/html'});
        res.end(data);
    });
});

Do the same in the '/do-something' request and you will see the IO logs:

BASH

2014-04-30    13:09:05    +0200    7048a612-dd8a-4677-aa32-49d0a5171208    1    GET /hello    0    OK    INTERFACE    SERVICE_ENTER        
2014-04-30    13:09:05    +0200    7048a612-dd8a-4677-aa32-49d0a5171208    1    Read    2    OK    FILE    IO_ENTER        Hello.html
2014-04-30    13:09:05    +0200    7048a612-dd8a-4677-aa32-49d0a5171208    1    Read    4    OK    FILE    IO_EXIT        Hello.html
2014-04-30    13:09:05    +0200    7048a612-dd8a-4677-aa32-49d0a5171208    1    GET /hello    6    OK    INTERFACE    SERVICE_EXIT        
2014-04-30    13:09:08    +0200    bdc2970f-6045-4c9e-b141-0f53cc707b94    2    GET /do-something    0    OK    INTERFACE    SERVICE_ENTER        
2014-04-30    13:09:08    +0200    bdc2970f-6045-4c9e-b141-0f53cc707b94    2    GetCustomer    1    OK    SAP    IO_ENTER        http://sap.e2e.ch:3000/
2014-04-30    13:09:10    +0200    bdc2970f-6045-4c9e-b141-0f53cc707b94    2    GetCustomer    2386    OK    SAP    IO_EXIT        http://sap.e2e.ch:3000/
2014-04-30    13:09:10    +0200    bdc2970f-6045-4c9e-b141-0f53cc707b94    2    GetCustomerDetail    2386    OK    DB    IO_ENTER        localhost/mongodb/
2014-04-30    13:09:11    +0200    bdc2970f-6045-4c9e-b141-0f53cc707b94    2    GetCustomerDetail    2855    ERROR    DB    IO_EXIT        localhost/mongodb/
2014-04-30    13:09:11    +0200    bdc2970f-6045-4c9e-b141-0f53cc707b94    2    GET /do-something    2857    OK    INTERFACE    SERVICE_EXIT        
2014-04-30    13:09:20    +0200    b71b24a9-cc37-473d-88aa-fb840ab159bb    3    GET /goodbye    0    OK    INTERFACE    SERVICE_ENTER        
2014-04-30    13:09:20    +0200    b71b24a9-cc37-473d-88aa-fb840ab159bb    3    GET /goodbye    1    OK    INTERFACE    SERVICE_EXIT

You can download the complete example project of tutorial 3.

Related Pages:

Documentation of the E2E Transaction Logger

Tutorial 1: Logging the Transactions of a Simple HTTP Server

Tutorial 2: Backend Access

Tutorial 3: Express

Download Example Project