I can not omit the huge impact that the NodeJS project is having as a server side solution with performance and features for new projects nowadays. As i wrote yesterday, i attended the Startechconf and at least two companies are putting their efforts to move to NodeJS as backend solution for their web infraestructure in a few projects: Yahoo and ForkHQ.
I did not know too much about NodeJS, so i dedicated some time to read the documentation and papers available, so being a web server side guy i would like to share my opinion, because i listen too much about that everybody must move to NodeJS.
The primary feature of NodeJS is that provides a framework based in a language thats handled by thousands of people: Javascript, if you are a real web developer you know what is JavaScript and you know how to deal with it, so you can jump directly from the client to the server side and write your own implementation, based on an event driven infrastructure with reduced I/O and better performance than dynamic content generators available such as Ruby, Python or PHP. It’s pretty interesting as technology which expose new possibilities to improve backend sides, but you must know when and where to use it.
The good thing is that Node abstract you from the dirty low level concepts of a web server like threading, shared memory, asynchronous sockets, reduced I/O, etc. But this have a cost, this is not magic, is just cool, because it works and have demonstrated to perform very well and have a level of trust as is written on top of V8 JavaScript engine supported by Google. The cost of an event driven solution is that if for some reason the program have an exception, the whole service will block or even crash depending of the case, so you must be aware because if something similar happen. As an example, if some Apache context fails, it will kill the process or thread and start a new one, which is not the case of a common event driven web server. What happen if you have 1000 connections transferring data and the program fail ?, it will be critical, and this things happens when working in high production environment, if you have 50 requests per day you are safe and you can stop reading now 
Node fills fine if you have thousands of incoming connections and your computing time is reduced, but if you will work with some complexity querying a database, doing some memcache or similar, you should start considering different options.
From now i start talking about solutions for really higher performance, Node is fast, but you cannot compare it with Apache, because Apache is the slowest web server available, compare it with NginX or Monkey. I will do a test now using the Apache Benchmark Utility comparing the NodeJS hello world example against Monkey which will serve a file which contains the Hello World message, the benchmark utility will perform 100.000 requests through 5000 concurrent connections.
NodeJS Benchmark
edsiper@monotop:/home/edsiper/# ab -n 100000 -c 5000 http://localhost:8888/
This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking localhost (be patient)
Completed 10000 requests
Completed 20000 requests
Completed 30000 requests
Completed 40000 requests
Completed 50000 requests
Completed 60000 requests
Completed 70000 requests
Completed 80000 requests
Completed 90000 requests
Completed 100000 requests
Finished 100000 requests
Server Software:
Server Hostname: localhost
Server Port: 8888
Document Path: /
Document Length: 11 bytes
Concurrency Level: 5000
Time taken for tests: 9.403 seconds
Complete requests: 99747
Failed requests: 0
Write errors: 0
Total transferred: 7481025 bytes
HTML transferred: 1097217 bytes
Requests per second: 10608.48 [#/sec] (mean)
Time per request: 471.321 [ms] (mean)
Time per request: 0.094 [ms] (mean, across all concurrent requests)
Transfer rate: 776.99 [Kbytes/sec] received
The NodeJS server was capable to serve 10608 requests per second and took 9 seconds to serve the 100.000 requests. Now let’s see how Monkey did…
Monkey HTTP Daemon Benchmark
edsiper@monotop:/home/edsiper/# ab -n 100000 -c 5000 http://localhost:2001/h.txt
This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking localhost (be patient)
Completed 10000 requests
Completed 20000 requests
Completed 30000 requests
Completed 40000 requests
Completed 50000 requests
Completed 60000 requests
Completed 70000 requests
Completed 80000 requests
Completed 90000 requests
Completed 100000 requests
Finished 100000 requests
Server Software: Monkey/0.30.0
Server Hostname: localhost
Server Port: 2001
Document Path: /h.txt
Document Length: 13 bytes
Concurrency Level: 5000
Time taken for tests: 5.718 seconds
Complete requests: 100000
Failed requests: 0
Write errors: 0
Total transferred: 20300000 bytes
HTML transferred: 1300000 bytes
Requests per second: 17489.54 [#/sec] (mean)
Time per request: 285.885 [ms] (mean)
Time per request: 0.057 [ms] (mean, across all concurrent requests)
Transfer rate: 3467.16 [Kbytes/sec] received
Monkey did 17.489 requests per second and took 5.7 seconds to serve the 100.000 requests. Ooops!
The impressive results are even better, because Monkey performed 100.000 I/O to retrieve a file from the hard disk and also send a couple of extra bytes one each response (Monkey does not cache file contents or metadata). Serve a file is a slow process due to I/O, so i will do a test later with the same case serving some fixed content through a plugin (something similar to what Node is doing in the test example).
What am trying to say here, is that depending of what are you trying to accomplish and the complexity of your backend., NodeJS can be the solution for your environment as well you could need something even more scalable like Monkey, but the learning curve of NodeJS is short and the learning curve of Monkey is a little high, but this last one provides a better performance because all is well written in C, as well any extension through the C API interface requires some knowledge which in NodeJS are hidden, you have to balance between goals, knowledge, learning curve and deadlines.
[UPDATE]:
- Joe provide me a new code to launch Node with multiple workers, so Node increase the performance, the new values were updated.
