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From Clive Cox ...@seldon.io>
Subject Re: Go / Python Sharing
Date Mon, 08 Jul 2019 08:28:45 GMT
Thanks for all the informative replies.

 In our case the Python and Go would be in separate processes. So for that
as I understand the conversation so far the options are:

   - Use of Plasma. This requires pending updates for the current Go
   implementation? (happy to help here)
   - IPC - but this will require sending the data over the wire?

Thanks,

 Clive





On Mon, 8 Jul 2019 at 09:05, Uwe L. Korn <uwelk@xhochy.com> wrote:

> Hello all,
>
> I've been using the in-process sharing method for quite some time for the
> Python<->Java interaction and I really like the ease of doing it all in the
> same process. Especially as this avoids any memory-copy or shared memory
> handling. This is really useful for the case where you only want to call a
> single routine in another language.
>
> Thus I would really like to see this also implemented for Go (and Rust) so
> that one can build custom UDFs in it and use them from Python code. The
> pre-conditions for this are that we have IPC tests that verify that both
> libraries use the exact same memory layout and that we can pull out the
> memory pointer from the Go Arrow structures into the C++ memory structures
> and also keep a reference between both so that memory tracking doesn't
> deallocate the underlying memory. For that we have in Python the
> pyarrow.foreign_buffer
> https://github.com/apache/arrow/blob/1b798a317df719d32312ca2c3253a2e399e949b8/python/pyarrow/io.pxi#L1276-L1292
>  function.
>
> For the Go<->Python case, I would though recommend to solve this as a
> Go<->C++ interface as this would make interaction for all the libraries
> based on the C++ one (like R, Ruby, ..) possible.
>
> Uwe
>
> On Mon, Jul 8, 2019, at 9:57 AM, Miki Tebeka wrote:
>
> My bad, IPC in Go seems to be implemented -
> https://issues.apache.org/jira/browse/ARROW-3679
>
> On Mon, Jul 8, 2019 at 10:18 AM Sebastien Binet <seb.binet@gmail.com>
> wrote:
>
> As far as i know, Go does support IPC (as in the arrow IPC format)
>
> Another option which has been discussed at some point was to have a shared
> memory allocator so the arrow arrays could be shared between processes.
>
> I haven't looked in details what implementing plasma support for Go would
> need on the Go side...
>
> -s
>
>
> sent from my droid
>
> On Mon, Jul 8, 2019, 08:29 Miki Tebeka <miki@353solutions.com> wrote:
>
> Hi Clive,
>
> I'd like to understand the high level design for a system where a Go
> process can communicate an Arrow data structure to a python process on the
> same CPU
>
> I see two options
> - Different processes with hared memory, probably using plasma
> - Same process. The either Go uses Python shared library or Python using
> Go compiled to shared library (-build-mode=c-shared)
>
>
> - and for the python process to zero-copy gain access to that data, change
> it and inform the Go process.  This is low latency so I don't want to save
> to file.
>
> IIRC arrow is not built for mutation. You build an Array/Table once and
> then use it.
>
> Would this need the use of Plasma as a zero-copy store for the data
> between the two processes or do I need to use IPC? But with IPC you are
> transferring the data which is not needed in this case as I understand it.
> Any pointers to examples would be appreciated.
>
> See above about options. Note that currently the Go arrow implementation
> doesn't support IPC or plasma (though it's in the works).
>
> Yoni & I are working on another option which is using the C++ arrow
> library from Go. It does support plasma and since it uses the same
> underlying C++ library that Python does you'll be able to pass a pointer
> around without copying data. It's at very alpha-ish state but you're more
> than welcomed to give it a try - https://github.com/353solutions/carrow
>
> Happy hacking,
> Miki
>
>
>

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