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Websocket should only call async_close once #4848

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merged 3 commits into from
Jan 12, 2024
Merged

Websocket should only call async_close once #4848

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8ef2cad
Websocket should only call async_close once
ximinez Dec 6, 2023
f3a3b61
[FOLD] On second thought, don't need the closing_ flag
ximinez Dec 7, 2023
4029ca2
Merge remote-tracking branch 'upstream/develop' into ws-async-close
ximinez Jan 10, 2024
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8 changes: 8 additions & 0 deletions src/ripple/server/impl/BaseWSPeer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,7 @@
#include <boost/beast/core/multi_buffer.hpp>
#include <boost/beast/http/message.hpp>
#include <boost/beast/websocket.hpp>

#include <cassert>
#include <functional>

Expand All @@ -52,6 +53,9 @@ class BaseWSPeer : public BasePeer<Handler, Impl>, public WSSession
boost::beast::multi_buffer rb_;
boost::beast::multi_buffer wb_;
std::list<std::shared_ptr<WSMsg>> wq_;
/// The socket has been closed, or will close after the next write
/// finishes. Do not do any more writes, and don't try to close
/// again.
bool do_close_ = false;
boost::beast::websocket::close_reason cr_;
waitable_timer timer_;
Expand Down Expand Up @@ -256,6 +260,8 @@ BaseWSPeer<Handler, Impl>::close(
return post(strand_, [self = impl().shared_from_this(), reason] {
self->close(reason);
});
if (do_close_)
return;
do_close_ = true;
if (wq_.empty())
{
Expand Down Expand Up @@ -348,6 +354,7 @@ BaseWSPeer<Handler, Impl>::on_write_fin(error_code const& ec)
return fail(ec, "write_fin");
wq_.pop_front();
if (do_close_)
{
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Should do_close_ be reset to false here? What if on_write_fin is called again?

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Actually, it doesn't look like it's needed since write() is not going to be called in on_write_fin() if do_close_ is true and send() is not going to call write() because closing_ is true. Then I don't think two flags are needed. Can keep do_close_ and have the check on line 264 and remove do_close_ on line 280. The check on line 264 prevents from initiating async_close again in close(). And do_close_ set to true will allow async_close in on_write_fin() if the queue was not empty when close() was called.

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Great question. I don't think that setting do_close_ to false is a good idea, though. Then, if wq_ is not empty we'd call on_write(). We're trying to shut things down.

If it's a problem that we need to address, and it feels like maybe it is, we could add yet another data member bool closed_ and set it true just as soon as we're inside this if. That would make this if look like...

    if (do_close_ && !closed)
    {
        closed = true;
        assert(closing_);
        ...
    }
    else if (!wq_.empty() && !closed)

But I don't like the idea of adding yet another bool. Perhaps it would work better with an enum for a state machine?

enum class Finish {
    not_closing,
    closing,
    do_close,
    closed
};

Just a thought...

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Thanks for the feedback. Coincidentally, I had the realization about not needing closing_ while having dinner, and came in to fix it before I even saw your comments. 😀

impl().ws_.async_close(
cr_,
bind_executor(
Expand All @@ -356,6 +363,7 @@ BaseWSPeer<Handler, Impl>::on_write_fin(error_code const& ec)
&BaseWSPeer::on_close,
impl().shared_from_this(),
std::placeholders::_1)));
}
else if (!wq_.empty())
on_write({});
}
Expand Down