supervisor is an application that builds in an HTTP server for various purposes. Because I was familiar with Medusa (because Zope uses Medusa too), Supervisor uses it to service HTTP requests.

There is a bit of code in Supervisor that allows for an "up check" by sending an HTTP request, to which supervisor will respond with an two-byte response: "OK". The code in supervisor that does this looks like this:

    class OKView:
        delay = 0
        def __init__(self, context):
            self.context = context

        def __call__(self):
            return {'body':'OK'}

This gets called whenever anybody asks for "/ok.html" on the Supervisor http port.

Here's the output for running "ab" against this view:

   [chrism@vitaminf ~]$ ab -n 1000 -c10 http://127.0.0.1:9001/ok.html
   This is ApacheBench, Version 2.0.40-dev <$Revision: 1.146 $> apache-2.0
   Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
   Copyright 2006 The Apache Software Foundation, http://www.apache.org/

   Benchmarking 127.0.0.1 (be patient)
   Completed 100 requests
   Completed 200 requests
   Completed 300 requests
   Completed 400 requests
   Completed 500 requests
   Completed 600 requests
   Completed 700 requests
   Completed 800 requests
   Completed 900 requests
   Finished 1000 requests

   Server Software:        Medusa/1.11
   Server Hostname:        127.0.0.1
   Server Port:            9001

   Document Path:          /ok.html
   Document Length:        2 bytes

   Concurrency Level:      10
   Time taken for tests:   0.851922 seconds
   Complete requests:      1000
   Failed requests:        0
   Write errors:           0
   Total transferred:      124000 bytes
   HTML transferred:       2000 bytes
   Requests per second:    1173.82 [#/sec] (mean)
   Time per request:       8.519 [ms] (mean)
   Time per request:       0.852 [ms] (mean, across all concurrent requests)
   Transfer rate:          142.03 [Kbytes/sec] received

   Connection Times (ms)
                 min  mean[+/-sd] median   max
   Connect:        0    0   0.4      0       6
   Processing:     1    7   3.8      6      20
   Waiting:        0    6   3.8      5      20
   Total:          1    7   3.8      6      20

   Percentage of the requests served within a certain time (ms)
     50%      6
     66%      7
     75%     11
     80%     11
     90%     12
     95%     14
     98%     17
     99%     18
    100%     20 (longest request)

That's 1173 req/sec. Just for fun I figured I'd try the same trick in Zope 2, using a Zope 3 view and using Repoze to allow the server to be the Zope 3 WSGI server. Here's the code (I'll omit the ZCML that wires it up for brevity):

    class OKView:
        def __init__(self, context, request):
            self.context = context
            self.request = request

        def __call__(self):
            return 'OK'

I wired that up so it would get invoked when I visited Zope at "/ok.html". Here's "ab" output for 1000 requests against that:

    [chrism@vitaminf ~]$ ab -n 1000 -c10 http://127.0.0.1:8080/ok.html
    This is ApacheBench, Version 2.0.40-dev <$Revision: 1.146 $> apache-2.0
    Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
    Copyright 2006 The Apache Software Foundation, http://www.apache.org/

    Benchmarking 127.0.0.1 (be patient)
    Completed 100 requests
    Completed 200 requests
    Completed 300 requests
    Completed 400 requests
    Completed 500 requests
    Completed 600 requests
    Completed 700 requests
    Completed 800 requests
    Completed 900 requests
    Finished 1000 requests

    Server Software:        zope.server.http
    Server Hostname:        127.0.0.1
    Server Port:            8080

    Document Path:          /ok.html
    Document Length:        2 bytes

    Concurrency Level:      10
    Time taken for tests:   3.554313 seconds
    Complete requests:      1000
    Failed requests:        0
    Write errors:           0
    Total transferred:      163000 bytes
    HTML transferred:       2000 bytes
    Requests per second:    281.35 [#/sec] (mean)
    Time per request:       35.543 [ms] (mean)
    Time per request:       3.554 [ms] (mean, across all concurrent requests)
    Transfer rate:          44.73 [Kbytes/sec] received

    Connection Times (ms)
                  min  mean[+/-sd] median   max
    Connect:        0    0   0.1      0       1
    Processing:    15   34  14.5     33     183
    Waiting:       13   30  14.5     29     176
    Total:         15   34  14.6     33     183

    Percentage of the requests served within a certain time (ms)
      50%     33
      66%     35
      75%     37
      80%     38
      90%     41
      95%     44
      98%     77
      99%    132
     100%    183 (longest request)

Ouch. That's 281 req/sec. Where the hell is all the time going? Transactions? Traversal overhead? Server overhead?