Le 17/07/2015 17:08, Matthew Flatt a écrit :
It's possible (but unlikely) for the thread bound to `a` to complete
and try to kill `b` before the variable `b` is initialized.
Ah ok, yes that is risky in this case, plus we didn't close the tcp
connection.
Here's what I'd do:
* Create a custodian to manage the thread, and shut the custodian down
instead of killing the thread. That way, in addition to killing the
thread, any network resources are also released.
* Instead of starting a timer thread, use `sync/timeout`.
(define (foo)
(define c (make-custodian))
(define t (parameterize ([current-custodian c])
(thread
(λ ()
(let-values ([(p-in p-out)
(tcp-connect "smtp.gmail.com" 5887)])
(printf "Server port is good"))))))
(displayln `(hello world))
(unless (sync/timeout 2 t) ; produces #f on timeout
(printf "Server port is not good")
(custodian-shutdown-all c)))
That is an elegant solution :) . So I read the doc about custodian with
parameterize to know more, but it is always a little mysterious for me.
when : (parameterize ([current-custodian c])
We say that we run the code in the 'body' part with a c parameter that
contain an empty custodian.
But we never added something to c, how the connections are 'linked' to
c, when we use custodian-shutdown-all ? It is automatic for all
thread/network/streams etc... functions in the 'body' part of
(parameterize) ?
When we bind the (parameterize) to a variable, the type is the type of
last result in the 'body' part in (parameterize) ? , So as a thread is
an evt, we can use it in sync/timeout.
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