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/issues/793#issuecomment-199547343,https://api.github.com/repos/pydata/xarray/issues/793,199547343,MDEyOklzc3VlQ29tbWVudDE5OTU0NzM0Mw==,1217238,2016-03-22T00:01:52Z,2016-03-22T00:01:52Z,MEMBER,"This should be pretty easy -- we'll just need to add `lock=threading.Lock()` to this line:
https://github.com/pydata/xarray/blob/v0.7.2/xarray/backends/common.py#L165

The only subtlety is that this needs to be done in a way that is dependent on the version of dask, because the keyword argument is new -- something like `if dask.__version__ > '0.8.1'`.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,140291221
https://github.com/pydata/xarray/issues/793#issuecomment-196924992,https://api.github.com/repos/pydata/xarray/issues/793,196924992,MDEyOklzc3VlQ29tbWVudDE5NjkyNDk5Mg==,1217238,2016-03-15T17:04:57Z,2016-03-15T17:27:29Z,MEMBER,"I did a little digging into this and I'm pretty sure the issue here is that HDF5 [cannot do multi-threading](https://www.hdfgroup.org/hdf5-quest.html#gconc) -- at all. Moreover, many HDF5 builds are not thread safe.

Right now, we use a single shared lock for all _reads_ with xarray, but for writes we rely on dask.array.store, which [only uses different locks for each array it writes](https://github.com/dask/dask/blob/0.8.1/dask/array/core.py#L1968). Because @pwolfram's HDF5 file includes multiple variables, each of these gets written with their own thread lock -- which means we end up writing to the same file simultaneously from multiple threads.

So what we could really use here is a `lock` argument to `dask.array.store` (like `dask.array.from_array`) that lets us insist on a using a shared lock when we're writing HDF5 files. Also, we may need to share that same lock between reading and writing data -- I'm not 100% sure. But at the very least we definitely need a lock to stop HDF5 from trying to do multi-threaded writes, whether that's to the same or different files.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,140291221
https://github.com/pydata/xarray/issues/793#issuecomment-195637636,https://api.github.com/repos/pydata/xarray/issues/793,195637636,MDEyOklzc3VlQ29tbWVudDE5NTYzNzYzNg==,1217238,2016-03-12T02:19:18Z,2016-03-12T02:19:18Z,MEMBER,"I'm pretty sure we now have a thread lock around all writes to NetCDF files, but it's possible that isn't aggressive enough (maybe we can't safely read and write a different file at the same time?). If your script works with synchronous execution I'll take another look.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,140291221