[Twisted-Python] Limiting the number of connections

[Miha Valencic]

Hi Adi!

Let me say upfront, that I'm not seeing any problems as of now. I am
asking this question out of engineering curiosity mostly and to know
whta to do if the problem would arose.

On Sun, Dec 9, 2012 at 10:44 AM, Adi Roiban <adi at roiban.ro> wrote:
> Hi,
> Just to summarize:
>
> * twisted.protocols.policies.LimitTotalConnectionsFactory is not what
> you want since the server is still listening on the port?
> LimitTotalConnectionsFactory is only returning a different protocol to
> handle the overflow.... closing the new connection is a way to handle
> the overflow.

I've never heard of LimitTotalConnectionsFactory before. This
particular mode of operation is desirable, since the client is
connected and disconnected. I was aiming more towards a usual approach
within webservers, where they have a certain amount of tcp workers,
and size of the waiting queue. That way the client does not get
disconnected, but waits a little and then gets a result. You know how
to webserver sometimes times out...

But, really, thinking about it, this factory is the right after all.
Akin to "http 550 service unavailable" when the service is not able to
respond to requests. If I understand the description correctly,
defining custom protocol that write "unavailable" and closes
connection, setting this protocol as a overflowProtocol would have the
exact behaviour I am after.

> * After a number of connections the server should stop listening on
> the port... and then tor re-start listening after the connections are
> closed?

No, the server shouldn't accept() the socket after n connections are
opened(). But see previous paragraph.

Regards, Miha.