On Sat, Sep 24, 2016 at 2:31 AM, Aarón Bueno Villares
<abv15...@gmail.com> wrote:
> I've tried to make a "synchronous" recaptcha verification using the
> underlaying Wt's IOService, asynchronous in nature. The code is the
> following one:
>
> // response_ready is just a std::condition_variable (I have tested with
> boost:: as well
> // for mutex, locks and the condition_variable and the result is the same).
> void google_recaptcha::p_verify(std::string const& recaptcha_response)
> {
> auto* client = new Wt::Http::Client(this);
> client->done().connect(this, &google_recaptcha::p_on_done);
>
> std::ostringstream os;
> os << "secret=" << st_server_secret << "&response=" <<
> recaptcha_response;
>
> Wt::Http::Message msg;
> msg.addBodyText(os.str());
> msg.setHeader("Content-Type", "application/x-www-form-urlencoded");
>
> client->post("https://www.google.com/recaptcha/api/siteverify";, msg);
>
> std::unique_lock<std::mutex> lk(wait_mutex);
> response_ready.wait_for(lk, std::chrono::seconds(15),
> [this]() -> bool { return
> b_is_done; });
> }
>
> void google_recaptcha::p_on_done(boost::system::error_code const& err,
> Wt::Http::Message
> const& response)
> {
> // Suppose everything works fine, to avoid dealing with exceptions
> (temporarily).
> std::cout << "IN SLOT" << std::endl;
>
> std::stringstream ss(response.body());
> boost::property_tree::ptree ptree;
> boost::property_tree::read_json(ss, ptree);
>
> auto success_optional = ptree.get_optional<bool>("success");
> o_verified.emit(success_optional.get()); // o_verified is a Wt::Signal.
>
> std::lock_guard<std::mutex> lk(wait_mutex);
> b_is_done = true;
> response_ready.notify_one();
> }
>
> And I don't know why, but when the JSignal is emitted (p_verified is
> connected to a JSignal), the thread is blocked at the `wait_for` line, and,
> after those 15 seconds of waiting, the `p_on_done` is method is called (it
> prints "IN SLOT"). So, they are not executed concurrently. Could it be
> because of the `strand` object which Wt's manages internally?
>
> I don't know if the `post` request ends and the `p_on_done` slot is which is
> waiting, or the `post` request is which waits. The thing is that it seems Wt
> tries to dispatch the `p_on_done` slots in the same thread than the
> `p_verify` slot's, so the block.
>
> How can I force `p_on_done` is executed concurrently? I'm interested in
> knowing both, the solution and why my approach is a blocking one.
>
> ------------------------------------------------------------------------------
>
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> witty-interest@lists.sourceforge.net
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>
Hi Aarón,
What is the number of threads? If 1, then it explains the problem -
the only available thread is blocked in response_ready.wait_for call.
--
Best regards,
Boris Nagaev
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