Today I tested ebb with simple merb application behind nginx and
apache servers in front.
It looks like ebb has poor performance when there is low concurrency
level.

My scenario:

I created merb application and created simple rack handler.
config/rack.rb

class HelloWorldHandler
  def initialize(app)
    @app = app
  end

  def call(env)
    if env['REQUEST_URI'] == '/handler_hello'
      return [
        200,
        {"Content-type", "text/html"},
        "Hello World"
      ]
    else
      return @app.call(env)
    end
  end
end

use HelloWorldHandler
run Merb::Rack::Application.new

(so when I get http://domain/handler_hello it returns "Hello World"
document.

First test:

$ merb -p 3000 -e production -a ebb -c 1
Starting merb server on port: 3000

$ ab -c 1 -n 10000 http://rackapp.local:3000/handler_hello
Requests per second:    4378.92 [#/sec] (mean)

So far it's very good.

I configured nginx to pass request to 3 ebb processes (nginx runs on
81 port).

$ merb -p 3000 -e production -a ebb -c 3
Starting merb server on port: 3000
Starting merb server on port: 3001
Starting merb server on port: 3002

$ ab -c 1 -n 10000 http://rackapp.local:81/handler_hello
Requests per second:    387.53 [#/sec] (mean)

$ ab -c 2 -n 10000 http://rackapp.local:81/handler_hello
Requests per second:    627.93 [#/sec] (mean)

As you see there is only 387req/s. But when I increase concurrency to
3 and later to 20:

$ ab -c 3 -n 10000 http://rackapp.local:81/handler_hello
Requests per second:    2251.51 [#/sec] (mean)

$ ab -c 20 -n 10000 http://rackapp.local:81/handler_hello
Requests per second:    2967.70 [#/sec] (mean)

There is some connection between number of processes and concurrency
level.

I tested ebb also with apache and there is similar relation with low
concurrency level and requests per seconds (but performance is much
worse):

Apache runs on 80 port:
$ ab -c 1 -n 100 http://rackapp.local/handler_hello
Requests per second:    36.45 [#/sec] (mean)

$ ab -c 2 -n 100 http://rackapp.local/handler_hello
Requests per second:    56.95 [#/sec] (mean)

$ ab -c 3 -n 200 http://rackapp.local/handler_hello
Requests per second:    73.14 [#/sec] (mean)

$ ab -c 20 -n 2000 http://rackapp.local/handler_hello
Requests per second:    556.18 [#/sec] (mean)

$ ab -c 100 -n 2000 http://rackapp.local/handler_hello
Requests per second:    791.16 [#/sec] (mean)

$ ab -c 200 -n 10000 http://rackapp.local/handler_hello
Requests per second:    2881.07 [#/sec] (mean)

I tested nginx and apache with the same application but as application
server thin and mongrel. Results for low concurrency level was much
much better than for ebb.

# thin
$ merb -p 3000 -e production -a thin -c 3
Starting merb server on port: 3000
Starting merb server on port: 3001
Starting merb server on port: 3002

# apache
$ ab -c 1 -n 10000 http://rackapp.local/handler_hello
Requests per second:    1459.45 [#/sec] (mean)

# nginx
$ ab -c 1 -n 10000 http://rackapp.local:81/handler_hello
Requests per second:    1978.73 [#/sec] (mean)

# mongrel
$ merb -p 3000 -e production -a mongrel -c 3
Starting merb server on port: 3000
Starting merb server on port: 3001
Starting merb server on port: 3002

# apache
$ ab -c 1 -n 10000 http://rackapp.local/handler_hello
Requests per second:    987.58 [#/sec] (mean)

# nginx
$ ab -c 1 -n 10000 http://rackapp.local:81/handler_hello
Requests per second:    1184.62 [#/sec] (mean)

Requests per second:    4253.11 [#/sec] (mean)

But when I use httperf results are much worse:

Request rate: 542.9 req/s (1.8 ms/req)

When I use thin or mongrel results are very similar regardless I use
httperf or ab.

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