html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,performed_via_github_app,issue
https://github.com/pydata/xarray/pull/2011#issuecomment-376145446,https://api.github.com/repos/pydata/xarray/issues/2011,376145446,MDEyOklzc3VlQ29tbWVudDM3NjE0NTQ0Ng==,6815844,2018-03-26T12:16:12Z,2018-03-26T12:16:12Z,MEMBER,"Ah, you are right.
The only way to realize rolling.periodic with dask would be to manually attach a chunk in the other side to the boundaries, construct rolling window array and then remove unnecessary boundaries by slicing.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,308039063
https://github.com/pydata/xarray/pull/2011#issuecomment-375835173,https://api.github.com/repos/pydata/xarray/issues/2011,375835173,MDEyOklzc3VlQ29tbWVudDM3NTgzNTE3Mw==,6815844,2018-03-24T01:07:32Z,2018-03-24T01:07:32Z,MEMBER,"Some comments.

+ We need to also support a dask array.
Can you update `dask_array_op.rolling_window`? Maybe [this page](http://dask.pydata.org/en/latest/array-ghost.html#boundaries) would help for the implementation.

We use this here 
https://github.com/pydata/xarray/blob/7c2c43ce6b1792e1193635ab9b64fd248266f632/xarray/core/dask_array_ops.py#L78-L79

I suspect this would be already working, but it would be nice if we can add some test cases.

+ Maybe we can also add `boundary='reflect'` option to make this as similar to `dask.ghost`.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,308039063
https://github.com/pydata/xarray/pull/2011#issuecomment-375833339,https://api.github.com/repos/pydata/xarray/issues/2011,375833339,MDEyOklzc3VlQ29tbWVudDM3NTgzMzMzOQ==,6815844,2018-03-24T00:45:25Z,2018-03-24T01:03:50Z,MEMBER,"Thanks for sending a PR.

> is fill_value='periodic' a good api?

Maybe better API would be `boundary='peiodic'` (see [comments](https://github.com/pydata/xarray/issues/2007#issuecomment-375828864)), but changing the public API is not an easy task.
Let's keep it now as is and decide it later.

> should the fill_value keyvalue be ported to rolling?

I don't think so. I think we can keep rolling as similar to that of pandas,
and this option should be specific to `construct` method.

> should this also be mentioned in the docs for rolling (I only learned about rolling.construct yesterday)

I think at least we need to add this to the docstring of `construct`.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,308039063