For my curiosity, what kind of interface are you using for async ?
2014-06-29 11:02 GMT+02:00 Alon Bar-Lev <alon.bar...@gmail.com>: > Hi, > > Thank you for adding this, I can understand how it works, and it will > provide a service for async that is written from scratch. I tried to > evaluate the amount of changes that required in my simple case to use > this interface and currently it is much too large, so I will not be > able to actually use it in the near future. > > Thanks! > Alon > > On Fri, Jun 6, 2014 at 9:48 AM, Guillaume Nodet <gno...@apache.org> wrote: > > I've enhanced SSHD to be able to provide fully non-blocking io on both > > client channels and server commands. > > A client side example is shown at > > > > > https://github.com/apache/mina-sshd/blob/master/sshd-core/src/test/java/org/apache/sshd/ClientTest.java#L171 > > A server side example: > > > > > https://github.com/apache/mina-sshd/blob/master/sshd-core/src/test/java/org/apache/sshd/util/AsyncEchoShellFactory.java > > > > I would appreciate any input ... > > > > > > 2014-04-20 0:33 GMT+02:00 Alon Bar-Lev <alon.bar...@gmail.com>: > > > >> On Sun, Apr 20, 2014 at 1:19 AM, Guillaume Nodet <gno...@apache.org> > >> wrote: > >> > 2014-04-19 20:43 GMT+02:00 Alon Bar-Lev <alon.bar...@gmail.com>: > >> > > >> >> On Sat, Apr 19, 2014 at 9:15 PM, Guillaume Nodet <gno...@apache.org> > >> >> wrote: > >> >> > Sshd internally uses nio2 by default, which is not based on > selectors, > >> >> but > >> >> > non blocking operations. > >> >> > > >> >> > On the client part of SSHD, things are mostly asynchronous already: > >> >> > #1 SshClient#connect returns a future on which you can set a > >> callback > >> >> > and that you can use to retrieve the ClientSession asynchronously > >> >> > #2 You need to use ClientSession#addXxxIdentity and then > >> >> > ClientSession#auth which is also asynchronous > >> >> > #3 You then create a channel, and actually operning the channel > is > >> >> also > >> >> > asynchronous > >> >> > #4 Closing channels is also asynchronous > >> >> > > >> >> > I think the only missing part is really the streams on the > >> ClientChannel > >> >> > which are using InputStream and OutputStream. > >> >> > If we replace them with an AsynchronousByteChannel, I think we > would > >> be > >> >> > fully async. > >> >> > >> >> Thank you for your response, Our definition of async is very > >> different... > >> >> :) > >> >> > >> >> I do not think this module is sufficient to what I target. I see the > >> >> number of threads created within the library core and the logic that > >> >> is out of reach. > >> > > >> > > >> >> This ssh library is great, splitting it into two logic only and > >> >> communication layers will enable to go fully async. The logic layer > >> >> should not have any thread. A default implementation of communication > >> >> layer can be provided, but is optional. The difference from the world > >> >> I coming for is that Future handling is much more complex than having > >> >> control queue. > >> >> > >> > > >> > Not sure exactly what you're talking about here. > >> > > >> > Afaik, the only place where the ssh layer actually create a thread in > >> when > >> > creating > >> > a client ChannelSession giving an InputStream which has to be read. > This > >> > thread creation can be easily avoided by using > >> ClientChannel#getInvertedIn() > >> > and writing to it. > >> > > >> > All other threads are communication threads only and are fully > controlled > >> > by > >> > the IoService layer which is pluggable. Both mina and nio2 > >> implementations > >> > use a fixed number of threads. But you can rewrite it if you need. > >> > > >> > I'm all for improving sshd, but I fear i'm not really seeing your > points > >> > clearly. > >> > >> Thank you for the discussion, I truly appreciate that. > >> > >> Having a method for async input/output of data stream will be a good > >> start within current implementation. > >> > >> Other than that it is a programming pattern discussion. I got the > >> information I needed, thank you! > >> > >> >> > >> >> Was just an idea, thank you for addressing. > >> >> > >> >> > > >> >> > 2014-04-19 15:57 GMT+02:00 Alon Bar-Lev <alon.bar...@gmail.com>: > >> >> > > >> >> >> On Sat, Apr 19, 2014 at 3:52 PM, Jon V. <sybersn...@gmail.com> > >> wrote: > >> >> >> > > >> >> >> > NIO controls and deals with the selectors. Async IO is a part of > >> that > >> >> but > >> >> >> > is not the same thing. Async io means that if a write cannot be > >> fully > >> >> >> > flushed. It will not block until it can be. NIO provides us the > >> >> events to > >> >> >> > tell us that data is available in the socket. > >> >> >> > >> >> >> Async IO is the ability for a single thread to perform > (multiplex) IO > >> >> >> (connect, read, write, close etc..) for multiple file descriptors. > >> >> >> > >> >> >> As far as I know, without NIO you cannot achieve that in Java. > >> >> >> > >> >> >> There is no sense in read or write without blocking if you cannot > >> wait > >> >> >> (vs actively poll) for an event. > >> >> >> > >> >> >> > On Apr 19, 2014 4:56 AM, "Alon Bar-Lev" <alon.bar...@gmail.com> > >> >> wrote: > >> >> >> > > >> >> >> > > On Sat, Apr 19, 2014 at 10:58 AM, Emmanuel Lécharny < > >> >> >> elecha...@gmail.com> > >> >> >> > > wrote: > >> >> >> > > > Le 4/19/14 9:45 AM, Alon Bar-Lev a écrit : > >> >> >> > > >> On Sat, Apr 19, 2014 at 10:38 AM, Emmanuel Lécharny < > >> >> >> > > elecha...@gmail.com> wrote: > >> >> >> > > >>> Le 4/19/14 9:13 AM, Alon Bar-Lev a écrit : > >> >> >> > > >>>> Hi, > >> >> >> > > >>>> > >> >> >> > > >>>> The mission of async is to avoid having threads at all, > or > >> at > >> >> >> least > >> >> >> > > O(1). > >> >> >> > > >>>> > >> >> >> > > >>>> As you have underline internal/private low level channels > >> for > >> >> >> socket > >> >> >> > > >>>> processing, and public high level channels to communicate > >> with > >> >> >> > > >>>> application, there should be a mechanism for library to > >> request > >> >> >> wake > >> >> >> > > >>>> up for these low level channels. > >> >> >> > > >>>> > >> >> >> > > >>>> Another option is to avoid using sockets at all within > the > >> >> >> > > >>>> implementation and require application to manage the > sockets > >> >> and > >> >> >> pipe > >> >> >> > > >>>> socket data into the library. > >> >> >> > > >>>> > >> >> >> > > >>>> I understand this is conceptional change than what we > have > >> now, > >> >> >> but > >> >> >> > > >>>> this what will enable scale without abusing system > threads > >> or > >> >> have > >> >> >> > > >>>> nondeterministic behaviour in high load. > >> >> >> > > >>> There are a few important things you have to know about > async > >> >> and > >> >> >> > > threads : > >> >> >> > > >>> - the extra cost for dealing with async connection is > around > >> >> 30%. > >> >> >> That > >> >> >> > > >>> all but free > >> >> >> > > >>> - a standard system can easily deal with a few thousands > of > >> >> threads > >> >> >> > > >>> > >> >> >> > > >>> Now, unless you define what is "high load", I don't really > >> see > >> >> what > >> >> >> > > kind > >> >> >> > > >>> of advantage we can get with an async implementation. > >> >> >> > > >>> > >> >> >> > > >>> FTR, when MINA was initially created, it was because there > >> was a > >> >> >> need > >> >> >> > > >>> for a system supporting potentially ten of thousands of > >> >> >> connections. Is > >> >> >> > > >>> that what you are targetting ? > >> >> >> > > >> Yes, using work threads that are derived per # of CPUs, no > >> more. > >> >> >> > > >> I am far from the pure "Java" world... but if async IO is > 30% > >> >> >> > > >> insufficient, maybe it worth to use libssh (C) and > communicate > >> >> with > >> >> >> it > >> >> >> > > >> using single socket from java, delegating IO outside of > java. > >> >> >> > > > IO are already delegated outside on Java. Eveything IO > related > >> is > >> >> >> > > > written in C and wrapped into Java class. > >> >> >> > > > > >> >> >> > > > The extra cost when using NIO is due to the management of > >> >> SelectorKey > >> >> >> > > > lists (with the various steps involved when dealing with > those > >> >> >> lists). > >> >> >> > > > > >> >> >> > > > All in all, when it comes to process IO, Java does not > really > >> add > >> >> >> some > >> >> >> > > > extra cost over a plain C implementation. It's not the same > >> story > >> >> >> when > >> >> >> > > > using NIO, especially when dealing with many concurrent > >> >> connections. > >> >> >> > > > > >> >> >> > > > >> >> >> > > So I am confused... Java does not add cost to async IO, but > NIO > >> >> does? > >> >> >> > > While NIO is the only interface to Java async IO? > >> >> >> > > > >> >> >> > >> >> > >> >
