Hi Cedric, a short answer: some of what you're trying to do has been traditionnally handled by object databases - multiple images retrieving and updating objects on a central store ensuring lots of good properties : see Gemstone.
Another answer, since you're looking at content-addressable distributed file systems. You can resolve the offline mode with object duplications (duplicate all objects in the images using them), and, when coming back online, have a merge approach to reconcile changes between versions of shared objects. Content-based hashes as identifiers in a distributed store have very nice properties for that purpose, because, if image C has modified object 0xcdaff3, then that object has in fact become object 0xee345d for that image (and the unmodified object is still 0xcdaff3 for images A and B). I wouldn't be against a slightly higher granularity when dealing with object transfers, however. Regards, Thierry 2017-10-27 10:43 GMT+02:00 Cédrick Béler <cdric...@gmail.com>: > > Nothing complex about two images exchanging messages, its not even complex > to transmit objects via fuel, you even transmit a debugger or any part of > the live environment or even make an "internet" of images that join objects > together. Sky is the limit. Pharo already provides you will all the > tools/libraries to do this. > > > Yes. That’s why I asked for better practices. > > > A streamsocket (not to be confused with regular sockets) will delay the > messages (a collection of bytes) until they arrive to the receiver or until > they have reached the timeout period. Offline mode is pretty much > obligatory even for plain old internet web apps because of drops in > connection or the plain fact a connection can become slow. > > > Offline mode is to me of first importance. > > Let’s say I have a sets of Pharo app (nodes). > Each one are independent running on different devices/computers. > > I want to exchange information between them according to some kind of > contracts and also on connection availability. > > What I find different from usual message exchanges between two images is > that I want to have full control on it. Plus I consider images offline by > default (meaning two images have different versions of the same info). So > conflict is the norm. > > Also, I don’t want to send message remotely (with behavior), I just want > to send/share an information and sync them (when possible). > > Connection between 2 images can be through a network but eventually > through a serial connection (usb cable, Bluetooth,...). > > So what I try to do as a proto is having connection controlled by my apps > (I put the app offline (not by switching off wifi but by switching > logically). I can see nodes availability and activate connexion manually > then see if conflict resolution is ok, + I log every connecitions changes > and exchanges). This is my plans for now but it may change ! ^^ > > > I used streamsockets in my Pharo to Python bridge (Atlas) because the > execution was not necessary synchronous , I was sending Python command to a > 3d application from Pharo and I had to make sure that the bridge was > working even in the case of a command that could take hours to execute like > a rendering process. > > > I’ll look at stream sockets and mq stuffs. > > > Cheers, > > Cédrick > > > One cool trick I did was to send the Python errors back to Pharo and > trigger them as Pharo's regular MessageNotUnderstood , this is a nice way > to make sure that you can fix a wrong message after it has been executing > without going to the image that is executing it. > > The limitation with sockets which what every frameworks uses because AFAIK > they are the only means to communicate remotely is that they are not top > performance so that mean that you can send long loops but executing > communication inside long loops will either slow you down considerably or > simply timeout your socket. Sockets can timeout from both ends if they feel > that for some reason they lost communication with the other side and > reached their timeout period. Timeout period is customization. > > This is a problem I did not tackle with my implementation because I dont > think there can be an actual practical solution better than avoiding this > scenario. > > Only shared memory seems to overcome this but it can be used only locally > and not remotely (aka on same computer) . > > On Wed, Oct 25, 2017 at 4:41 PM Cédrick Béler <cdric...@gmail.com> wrote: > >> I had a look and this is not (natively) possible. >> >> The idea of the off-line mode would be to delay messages that are sent to >> the peer until a connection is established. >> >> I think I have to try to do it by myself (like having a list of >> information exchange that wait until a connexion is established). >> >> What I try to do is not as complex as two general image exchanging >> messages on objects (like on TelePharo). >> >> I just want a repository of information (mainly a collection of static >> information/data versions) on both peers to be synchronized when a >> connection is established. >> >> >> >> >> >> Le 25 oct. 2017 à 15:31, Denis Kudriashov <dionisi...@gmail.com> a écrit >> : >> >> What is offline mode? >> >> 2017-10-25 15:10 GMT+02:00 Cédrick Béler <cdric...@gmail.com>: >> >>> Thanks Denis. I will ! I knew I have seen a telephoto component that >>> could help but forgot about it ! >>> >>> Do you know if it’s possible to handle offline mode ? >>> >>> >>> >>> Le 25 oct. 2017 à 15:05, Denis Kudriashov <dionisi...@gmail.com> a >>> écrit : >>> >>> Look at Seamless https://github.com/dionisiydk/Seamless. >>> >>> 2017-10-25 14:21 GMT+02:00 Cédrick Béler <cdric...@gmail.com>: >>> >>>> Hi all, >>>> >>>> I want to connect two applications (1 by image, each one on a different >>>> computer) so as as to exchange information (data) between them. >>>> >>>> So my question is about the best (smalltalk) practices to connect two >>>> app/image and exchange data. >>>> >>>> I imagine either with a direct connection through a network (TCP >>>> Socket, Web socket, pure HTTP with Zinc) and/or with a serial connection. >>>> At first, without any « security ». But later, information exchanges >>>> will be encrypted. >>>> >>>> I’ve seen some information on how to use SerialPort, or even FileStream. >>>> I could do it (or at least simulate it with HTTP). What are the other >>>> options ? Socket ? >>>> Do we have P2P libs (I couldn’t find) with eventually discovery >>>> features ? >>>> >>>> Any comment / suggestion / pointers are greatly welcome. >>>> >>>> TIA. >>>> >>>> Cédrick >>>> >>> >>> >>> >> >>
