wsgi.simple_server in a mono threaded process that can handle only
5 requests at a time.
Even the doc recommands to setup Ceilometer through an other WSGI services
like Apache 'mod_wsgi', we can provide a better testing API server.
So this patch changes the default HTTP server to the werkzeug one with
a autodiscovery of number of workers that we can use.
The client queue of werkzeug is 128, so on a 4 cpus machine, ceilometer-api
can now handle 512 connections instead of 5.
Also the change adds references of how to deploy pecan application in
the documentation.
The config option enable_reverse_dns_lookup can be safely removed,
because werkzeug doesn't do any reverse dns lookup.
DocImpact: configuration options changed:
enable_reverse_dns_lookup removed, api_workers added
Change-Id: If7450b393ea88bc185e5c82b706ace9c38ce350e
09a2f0994f