added aiohttp_retry hint to README

README.md

@@ -11,6 +11,37 @@ with fsspec.open("swift://server/account/container/object.txt", "r") as f:
 
 `swiftspec` uses the environment variables `OS_STORAGE_URL` and `OS_AUTH_TOKEN` for authentication if available. To create these variables, you can use the `swift auth` command from the [python-swiftclient](https://docs.openstack.org/python-swiftclient/latest/cli/index.html).
 
+## fault tolerance / automatic retry
+
+Sometimes reading or writing from / to a swift storage might fail occasionally. If many objects are accessed, occasional failures can be extremely annoying and could be fixed relatively easily by retrying the request. Fortunately the `aiohttp_retry` package can help out in these situations. `aiohttp_retry` provides a wrapper around an `aiohttp` Client, which will automatically retry requests based on some user-provided rules. You can inject this client into the `swiftspec` filesystem using the `get_client` argument. First you'll have to define an async `get_client` function, which configures the `RetryClient` according to your preferences, e.g.:
+
+```python
+async def get_client(**kwargs):
+    import aiohttp
+    import aiohttp_retry
+    retry_options = aiohttp_retry.ExponentialRetry(
+            attempts=3,
+            exceptions={OSError, aiohttp.ServerDisconnectedError})
+    retry_client = aiohttp_retry.RetryClient(raise_for_status=False, retry_options=retry_options)
+    return retry_client
+```
+
+afterwards, you can use this function like:
+
+```python
+with fsspec.open("swift://server/account/container/object.txt", "r", get_client=get_client) as f:
+    print(f.read())
+```
+
+or:
+
+
+```python
+import xarray as xr
+ds = xr.Dataset(...)
+ds.to_zarr("swift://server/account/container/object.zarr", storage_options={"get_client": get_client})
+```
+
 ## Develop
 
 ### Code Formatting