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Wes McKinney commented on ARROW-1163: ------------------------------------- Along with the 0.5.0 release, we should have a blog post that explains how the object store works and call for contributions, which might help with recruiting some Java developers to get involved > [Plasma] Java client for Plasma > ------------------------------- > > Key: ARROW-1163 > URL: https://issues.apache.org/jira/browse/ARROW-1163 > Project: Apache Arrow > Issue Type: New Feature > Reporter: Philipp Moritz > > We should start thinking about how a Java client for plasma would look like. > Given the focus of arrow to support Python, C++ and Java really well, it is > the next important target after Python and C++. > My preliminary thoughts on it are the following ones: We can either go with > JNI and wrap the C++ client or (in my opinion preferable) write a pure Java > client. It would communicate with the Plasma store via Java flatbuffers over > sockets. > It seems that the only thing blocking a pure Java client at the moment is the > way we ship file descriptors for the memory mapped files between store and > client (see the file fling.cc in the Plasma repo). We would need to get rid > of that because there is no pure Java API that allows transferring file > descriptors over a process boundary. So the way to transfer memory mapped > files over process boundaries then is probably to use the file system and > keep the memory mapped files in the file system instead of unlinking them > immediately (as we do at the moment), so they can be opened by the client > process via their path. > The challenge in this case is how to clean the files up and make sure they > are not lying around if the plasma store crashes. One option is to store the > plasma store PID with the file (i.e. as part of the file name) and let the > plasma store clean them up the next time it is started); maybe there is OS > level support for temporary files we can reuse. > I probably won't get to this for a while, so if anybody needs this or has > free cycles, they should feel free to chime in. Also opinions on the design > are appreciated! > -- Philipp. -- This message was sent by Atlassian JIRA (v6.4.14#64029)