And for https://github.com/simonw/jupyterserverproxy-datasette-demo setting "absolute_url": True appears to fix the bug as well (it previously caused an infinite redirect loop but that seems not to happen any more with the latest base_url setting): https://github.com/simonw/jupyterserverproxy-datasette-demo/commit/880f9d50566357160b793557f145c99e74ad759a

Hooray! This is a really great fix, thanks.

Following on from @betatim's suggestion on Twitter, I've changed the proxy url to include 'absolute'.

python proxy_url = f'{base_url}proxy/absolute/8001/' This works both on Binder and locally, without using the path_from_header option. I've updated the demo repository. Sorry @simonw if I've led you down the wrong path!

Great! Yes, can confirm that this works on Binder. However, when I try to run the same code locally, I get an Internal Server Error when I try to access Datasette.

ERROR: Exception in ASGI application Traceback (most recent call last): File "/Volumes/Workspace/mycode/datasette-test/lib/python3.7/site-packages/uvicorn/protocols/http/httptools_impl.py", line 385, in run_asgi result = await app(self.scope, self.receive, self.send) File "/Volumes/Workspace/mycode/datasette-test/lib/python3.7/site-packages/uvicorn/middleware/proxy_headers.py", line 45, in __call__ return await self.app(scope, receive, send) File "/Volumes/Workspace/mycode/datasette-test/lib/python3.7/site-packages/datasette_debug_asgi.py", line 24, in wrapped_app await app(scope, recieve, send) File "/Volumes/Workspace/mycode/datasette-test/lib/python3.7/site-packages/datasette/utils/asgi.py", line 174, in __call__ await self.app(scope, receive, send) File "/Volumes/Workspace/mycode/datasette-test/lib/python3.7/site-packages/datasette/tracer.py", line 75, in __call__ await self.app(scope, receive, send) File "/Volumes/Workspace/mycode/datasette-test/lib/python3.7/site-packages/datasette/app.py", line 746, in __call__ raw_path = dict(scope["headers"])[path_from_header.encode("utf8")].split(b"?")[0] KeyError: b'x-original-uri' INFO: 127.0.0.1:49320 - "GET / HTTP/1.1" 500 Internal Server Error

I think the solution here may be to let the incoming x-original-uri header over-ride the raw_path used by Datasette. This may require a new Datasette setting - maybe this:

--config path_from_header:x-original-uri

Woohoo that worked!

Here's the output of the /-/asgi-scope plugin: {'client': ('10.12.3.15', 0), 'headers': [(b'cookie', b''), (b'upgrade-insecure-requests', b'1'), (b'dnt', b'1'), (b'accept-encoding', b'gzip'), (b'accept-language', b'en-US,en;q=0.5'), (b'accept', b'text/html,application/xhtml+xml,application/xml;q=0.9,image/' b'webp,*/*;q=0.8'), (b'user-agent', b'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:74.0) Gecko' b'/20100101 Firefox/74.0'), (b'x-scheme', b'https'), (b'x-original-uri', b'/user/wragge-datasette-test-czqms2oy/proxy/8001/-/asgi-scope'), (b'x-forwarded-proto', b'https,http'), (b'x-forwarded-port', b'443,80'), (b'x-forwarded-host', b'hub.gke.mybinder.org'), (b'x-forwarded-for', b'148.64.98.14,10.12.3.15'), (b'x-real-ip', b'148.64.98.14'), (b'connection', b'close'), (b'host', b'hub.gke.mybinder.org'), (b'x-forwarded-context', b'/user/wragge-datasette-test-czqms2oy/proxy/8001'), (b'x-proxycontextpath', b'/user/wragge-datasette-test-czqms2oy/proxy/8001')], 'http_version': '1.1', 'method': 'GET', 'path': '/-/asgi-scope', 'query_string': b'', 'raw_path': b'/-/asgi-scope', 'root_path': '', 'scheme': 'https,http', 'server': ('127.0.0.1', 8001), 'type': 'http'} From this output... it looks like the path being passed through to Datasette is still /-/asgi-scope here when I though it would be /user/wragge-datasette-test-czqms2oy/proxy/8001/-/asgi-scope

The original URL path (the one I want) is passed in the x-original-uri HTTP header.

I'm running this latest release like so:

Launch this binder: https://mybinder.org/v2/gh/wragge/datasette-test/master?urlpath=lab

Open the notebook.

In the notebook run this:

!pip install datasette-debug-asgi https://github.com/simonw/datasette/archive/7b205af0b53c92d17b69f8c95d70a24a0c06ebce.zip

And use this block to run Datasette:

```

Get current running servers

servers = list_running_servers()

Get the current base url

base_url = next(servers)['base_url']

Create a base url for Datasette suing the proxy path

proxy_url = f'{base_url}proxy/8001/'

Display a link to Datasette

display(HTML(f'

View Datasette (Click on the stop button to close the Datasette server)

Launch Datasette

!datasette -- results.db --port 8001 --config base_url:$proxy_url --config path_from_header:x-original-uri --config template_debug:1 ```

I have a hunch about this: maybe the URLs that work are the ones that use {{ base_url }} directly in the template, while the ones that break are the ones that reconstruct the URL based on the incoming path?

Aha! It turns out my demo at https://github.com/simonw/jupyterserverproxy-datasette-demo suffers from the same bug.

Here's the truncatted HTML for https://hub.gke.mybinder.org/user/wragge-datasette-test-czqms2oy/proxy/8001/results/articles ```html

home / results

Weird... the unit test I just added passes. So suggested facets look like they're OK.

And yet the demo in https://mybinder.org/v2/gh/wragge/datasette-test/master?urlpath=lab doesn't work.