twisted - locking threads when deferToThread is used

[Chris Mellon]

On 8/8/07, Chris Mellon <arkanes at gmail.com> wrote:
> On 8/8/07, Ladislav Andel <ladaan at iptel.org> wrote:
> > Hi,
> > I'm writing an application which will be periodically testing servers.
> > I will have a global list of these servers(domain names) and need to do
> > few tasks.
> > 1) DNS checks - I will use asynchronous twisted-names for it
> > - in case there is a difference comparing to the list it should update
> > the list(then also in DB)
> > 2) ICMP pings - should be also possible to do it asynchronously
> > 3) Blocking function which will be pinging with SIP requests
> > - here I will use function deferToThread to make it non-blocking.
> >
> > Questions:
> > 1) How do I lock each thread when writing to a global list in twisted?
> > 2) How will I put together all three results mentioned above in the
> > global list
> > - is it by using function callLater ?
> > 3) Could you help me with a rough skeleton of this application, please?
> >
> > Thank you,
> > Lada
> >
>
>
> deferToThread returns the result of the passed function in a Deferred.
> Callbacks and errbacks will be run in the main event loop, so you
> don't need to worry about thread safety of the callbacks, just of the
> function itself.
>
> The basic model would look something like this:
>
> def querySIP(what):
>     return sip.query(what) #native, *threadsafe*, blocking call
>
> sipquery = reactor.deferToThread(querySIP, what)
> sipquery.addCallback(lambda result: sip_results.append(result))
> sipquery.addErrback(log.err)
>


And, of course, deferToThread is a function in the
twisted.internet.threads module, not a method of the reactor.