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https://issues.apache.org/jira/browse/ARROW-4283?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17645386#comment-17645386
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Weston Pace edited comment on ARROW-4283 at 12/9/22 4:44 PM:
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Things have changed a bit since 2019. The {{RecordBatchFileWriter}} has an
asynchronous API now. It's currently exposed as a whole-file reading
{{AsyncGenerator}} (an iterator function that returns a promise each time you
call it) via {{RecordBatchFileWriter::OpenAsync}} and
{{RecordBatchFileWriter::GetRecordBatchGenerator}}. Although, under the hood,
there are {{ReadFooterAsync}}, {{ReadRecordBatchAsync}} methods that could be
exposed should more direct control be desired.
Adapting this pattern to the streaming reader should be pretty straightforward.
These methods all return {{arrow::Future}}. As far as I know no one has done
the neccesary work to plumb {{arrow::Future}} into a python async API (e.g.
{{asyncio}}).
Asynchronous methods in Arrow typically work by offloading the blocking I/O
calls to a global I/O thread pool (which can have more threads than there are
cores and should generally be sized appropriately for the I/O device). This
keeps the CPU threads free and non-blocking. To hook this into {{asyncio}} you
would probably want to call {{arrow::Future::AddCallback}} and then, in that
callback, schedule a task on some kind of python executor. In that python
executor task you will want to mark some kind of {{asyncio}} future complete
and this will presumably run any needed callbacks.
was (Author: westonpace):
Things have changed a bit since 2019. The {{RecordBatchFileWriter}} has an
asynchronous API now. It's currently exposed as a whole-file reading
{{AsyncGenerator}} (an iterator function that returns a promise each time you
call it) via {{RecordBatchFileWriter::OpenAsync}} and
{{RecordBatchFileWriter::GetRecordBatchGenerator}}. Although, under the hood,
there are {{ReadFooterAsync}}, {{ReadRecordBatchAsync}} methods that could be
exposed should more direct control be desired.
Adapting this pattern to the streaming reader should be pretty straightforward.
These methods all return {{arrow::Future}}. As far as I know no one has done
the neccesary work to plumb {{arrow::Future}} into a python async API (e.g.
{{asyncio}}).
Asynchronous methods in Arrow typically work by offloading the blocking I/O
calls to a global I/O thread pool (which can have more threads than there are
cores and should generally be sized appropriately for the I/O device). This
keeps the CPU threads free and non-blocking. To hook this into {{asyncio}} you
would probably want to call {{arrow::Future::AddCallback}} and then, in that
callback, schedule a task on some kind of python executor. In that python
executor task you will want to mark some kind of {{asyncio}} future complete.
> [Python] Should RecordBatchStreamReader/Writer be AsyncIterable?
> ----------------------------------------------------------------
>
> Key: ARROW-4283
> URL: https://issues.apache.org/jira/browse/ARROW-4283
> Project: Apache Arrow
> Issue Type: Improvement
> Components: Python
> Reporter: Paul Taylor
> Priority: Minor
>
> Filing this issue after a discussion today with [~xhochy] about how to
> implement streaming pyarrow http services. I had attempted to use both Flask
> and [aiohttp|https://aiohttp.readthedocs.io/en/stable/streams.html]'s
> streaming interfaces because they seemed familiar, but no dice. I have no
> idea how hard this would be to add -- supporting all the asynciterable
> primitives in JS was non-trivial.
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