Working example of using Async/Await

[Sarafudinov]

Hello, I’m working with s3fs and haven’t found any examples of how to work with asynchrony; after looking through your checklog I saw that you’ve already added functionality. Could you please tell me how to use asynchronous methods for reading/writing and listing files
the same question was asked in 2020
then this functionality was not ready and only a link to a small piece was provided https://s3fs.readthedocs.io/en/latest/#async

Thanks in advance for your attention!)

[martindurant]

What kind of workflow would you like? Perhaps I can sketch out what you need to do, and you help update the docs?

[Sarafudinov]

Thank you, I would like to learn more, see examples of how to use the reading (s3.open), writing and listing (s3.ls) methods in asynchronous code

1. I need the ability to asynchronously download files from a bucket (as far as I understand, this is the open_async method)
2. I would also like to see an example of asynchronously writing files to a bucket
3. and regarding the listing of files, I don’t quite understand whether there is an analogue when initializing s3 = S3FileSystem(asynchronous=True) since to work with the listing (s3.ls(path)) you have to use synchronous initialization s3 = S3FileSystem()

[Sarafudinov]

all I need is an example of how to read files from the bucket, write files to the bucket and look at the listing of files on the bucket

at the same time, so that it is all asynchronous
As far as I understand from your changelog, you have already implemented this, but I haven’t found any examples

2023.4.0
Add streaming async read file (#722)

or for now link only to the botocore library https://aiobotocore.readthedocs.io/en/latest/examples/s3/basic_usage.html

[martindurant]

Sorry to be slow, thanks for the ping.
Here is an example:

import asyncio

async def f():
    import fsspec
    mybucket = "mybucket"   # <- change this
    fs = fsspec.filesystem("s3", asynchronous=True, anon=False)
    print(await fs._ls(mybucket))
    await fs._pipe_file(f"{mybucket}/afile", b"hello world")
    print(await fs._cat_file(f"{mybucket}/afile"))

asyncio.run(f())

You should note that the file-like interface (via fs.open(...)) is not async, because the upstream python file-like object (io.IOBase) is not async. This is why open_async exists, but this "streaming" API is incomplete.

[Sarafudinov]

do not quite understand😅
As far as I understand, asynchronous reading is designed through s3fs.open_async()
in your example you indicate something like this:

async def async_read():
    s3 = S3FileSystem(..., asynchronous=True)
    fs = await s3.open_async(path, "rb")
    result = await fs.read()

this is what this asynchronous reading looks like + - I figured it out after digging through your git😁

is there any example when writing is used?

async def async_write(some_content):
    s3 = S3FileSystem(..., asynchronous=True)
    fs = await s3.open_async(path, "w")
    await fs.write(some_content)

since the only thing I found was also an issue #853

[martindurant]

No, we do not have asynchronous stream writing, sorry. If you can think of a way to do it, I would be happy.

[Sarafudinov]

Hello,
I tried to add the logic of asynchronous writing,
I hope this will somehow help in development!
#885