Posted by Gordon Burditt on 09/21/07 22:54

>>>>> You cannot, for example, have multiple instances of Apache listening on
>>>>> port 80 of a single IP address, and I thought assigning 255 IP
>>>>> addresses
>>>>> to a single web server went out with browsers that don't understand
>>>>> HTTP/1.1 and the Host: header.
>>>>>
>>>>
>>>> I didn't say anything about multiple instances on port 80, did I?
>>>>
>>>
>>> Actually you can, and often do, have multiple instances of Apache
>>> (effectively) listening on port 80..
>>>
>>> That's how virtual hosting and load balancing works.
>>
>> No. You can only have one instance of Apache running on port 80 on a
>> single machine.
>>
>> Virtual hosting works because that one instance has several hosts
>> defined. But it is still only one instance.
>>
>> Load balancing works because the instances of Apache are on different
>> systems.
>>
>
>Semantics.
>
>You can chain more listeners than one to a single port. At what point
>that becomes 'more than one instance tied to a port' as against 'one OS
>routine vectoring calls to multiple processes' is a moot one.

Let's see you set it up so that (a) all of the processes have
different user ids, none of them root, (b) the dispatcher process(es)
actually doing the listen() is(are) not running as root, (c) no use
of setuid-root programs, and (d) the dispatcher is able to dispatch
the requests to the process with the correct user id (based on the
Host: header).

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