[Nut-upsdev] Changes to upscli_connect

[Arjen de Korte]

Citeren Frédéric Bohé <fredericbohe op eaton.com>:

> I am currently working on the nut scanner. For detecting available upsd
> on the network, I rely on upscli_connect. The problem with this function
> is that it calls a blocking "connect" function.

This is a serious problem, not only for the nut-scanner but for  
basically all nut clients we currently bundle.

> So the nut-scanner is
> blocked while waiting for the TCP timeout when trying to connect to an
> IP without upsd available . Since this timeout may be rather long (3
> minutes on my host), I would like to add a timeout parameter to
> upscli_connect.

I don't think this is a good idea.

> I propose to add a upscli_tryconnect function accepting a timeout
> parameter, which will be the copy of the current upscli_connect + the
> management of the timeout. The upscli_connect will be only a wrapper on
> top of upscli_tryconnect, calling it without timeout.
> Please let me know if this makes sense to you.

The upscli_connnect() call should not block. If it does, that is a  
problem that needs fixing, rather than adding an timeout. On what kind  
of system did you test this? If I attempt to connect upsmon to a  
non-existing server socket, the following is shown (-DDD):

    0.001902     Trying to connect to UPS [myups op localhost]
    0.002667     UPS [myups op localhost]: connect failed: Connection  
failure: Network is unreachable
    0.002690     do_notify: ntype 0x0005 (COMMBAD)
    0.002704     Communications with UPS myups op localhost lost

Best regards, Arjen
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