Reactor dies unexpectedly about ione HOT 4 OPEN

Ione version is 1.2 (using cassandra-driver 1.0.0)
Ruby versions are 1.9.3, 2.0 and 2.1
Linux version 3.13.0-24-generic (buildd@batsu) (gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1))

from ione.

Yes, it looks like there is a possibility that a socket can be closed between the #closed? check in the reactor and the IO.select. It's very curious that it doesn't happen on OS X. It also doesn't seem to happen in JRuby (on OS X at least, but it feels like it should be the same in Linux).

I have two solutions to this, but first a workaround: schedule a timer and close sockets in the callback.

reactor.schedule_timer(0).on_complete do
  session.close
end

The handler is always called from the reactor thread so this ensures that the socket is properly closed without any racing.

The simplest fix to the underlying issue is to remove line 32 of lib/ione/io/base_connection.rb (https://github.com/iconara/ione/blob/master/lib/ione/io/base_connection.rb#L32). This will cause IO.select to raise an IOError in the situation where it could now raise TypeError because of the nil IO. That is something that the reactor expects (because there's always the possibility that a socket will be closed).

Could you try that out and see if it helps? If it does I can make a bug fix release.

A better solution is to rewrite socket operations so that they are always performed from the reactor thread. This is basically what happens when connecting or writing; the action is buffered and only performed when the socket is ready. #close should probably just set a flag that is acted on just before the select call. This will probably have to wait a bit, but it feels like a more robust solution. There's been a few issues with socket closing, and trying to make it work with concurrent modifications will just make it more complicated without adding any benefits.

from ione.

I've introduced your suggestion here datastax/ruby-driver@8c45eee, this should resolve issues that we faced in the ruby-driver.

I do think that the simples quickfix is to not set @io to nil and let the regular error handling mechanism take care of cleaning up closed sockets, but we don't need it with the fix I mentioned above.

Thanks for your help!

from ione.

I'll re-open this to use as a reminder to fix the underlying issue. The workaround should be applicable to all users of Ione in the meantime, if someone stumbles on this issue,

from ione.