Distributed data parallel training for streaming datasets
### Feature request

Any documentations for the the `load_dataset(streaming=True)` for (multi-node multi-GPU) DDP training? 

### Motivation

Given a bunch of data files, it is expected to split them onto different GPUs. Is there a guide or documentation?

### Your contribution

Does it requires manually split on data files for each worker in `DatasetBuilder._split_generator()`? What is`IterableDatasetShard` expected to do?
Hi ! According to https://huggingface.co/docs/datasets/use_with_pytorch#stream-data you can use the pytorch DataLoader with `num_workers>0` to distribute the shards across your workers (it uses `torch.utils.data.get_worker_info()` to get the worker ID and select the right subsets of shards to use)

<s> EDIT: here is a code example </s>
```python
# ds = ds.with_format("torch")
# dataloader = DataLoader(ds, num_workers=num_workers)
```

EDIT: `with_format("torch")` is not required, now you can just do
```python
dataloader = DataLoader(ds, num_workers=num_workers)
``` @cyk1337 does streaming datasets with multi-gpu works for you? I am testing on one node with multiple gpus, but this is freezing, https://github.com/huggingface/datasets/issues/5123 
In case you could make this work, could you share with me your data-loading codes?
thank you +1 This has been implemented in `datasets` 2.8:
```python
from datasets.distributed import split_dataset_by_node

ds = split_dataset_by_node(ds, rank=rank, world_size=world_size)
```

docs: https://huggingface.co/docs/datasets/use_with_pytorch#distributed i'm having hanging issues with this when using DDP and allocating the datasets with `split_dataset_by_node` 🤔

--- 
### edit
I don't want to pollute this thread, but for the sake of following up, I observed hanging close to the final iteration of the dataloader. I think this was happening on the final shard. First, I removed the final shard and things worked. Then (including all shards), I reordered the list of shards: `load_dataset('json', data_files=reordered, streaming=True)` and no hang. 

I won't open an issue yet bc I am not quite sure about this observation. @wconnell would you mind opening a different bug issue and giving more details?
https://github.com/huggingface/datasets/issues/new?assignees=&labels=&template=bug-report.yml

Thanks.