issue_comments

thanks so very much for the prompt attention and fix! Plus, the animated GIF showing the bug is just extra and I love it. Interactions like this are why I love open source.

I think what's happening here is Apache is actually making a request to /fixtures rather than making a request to /prefix/fixtures - and Datasette is replying to requests on both the prefixed and the non-prefixed paths.

This is pretty confusing! I think Datasette should ONLY reply to /prefix/fixtures instead and return a 404 for /fixtures - this would make things a whole lot easier to debug.

But shipping that change could break existing deployments. Maybe that should be a breaking change for 1.0.

On further thought I'm not going to do this. Having Datasette work behind a proxy the way it does right now is clearly easy for people to deploy (now that I've fixed the bugs) and I trust my improved tests to catch problems in the future.

OK, i think I got all of them this time!

The latest demo is now live at https://datasette-apache-proxy-demo.fly.dev/prefix/fixtures/sortable?_facet=pk2

I'm closing this issue, but feel free to re-open it if you spot any that I missed.

Ouch a nasty bug crept through there - https://datasette-apache-proxy-demo-j7hipcg4aq-uc.a.run.app/prefix/fixtures/compound_three_primary_keys says

500: name 'ds' is not defined

Adding that test found (I hope!) all of the remaining base_url bugs. There were a bunch! I think I finally get to close #838 too.

In the meantime I can catch these errors by changing the test to run each path twice, once with and once without the prefix. This should accurately simulate how Apache is working here.

This worked, I managed to get the tests to fail! Here's the change I made:

```diff diff --git a/tests/test_html.py b/tests/test_html.py index f24165b..dbdfe59 100644 --- a/tests/test_html.py +++ b/tests/test_html.py @@ -1614,12 +1614,19 @@ def test_metadata_sort_desc(app_client): "/fixtures/compound_three_primary_keys/a,a,a", "/fixtures/paginated_view", "/fixtures/facetable", + "/fixtures?sql=select+1", ], ) -def test_base_url_config(app_client_base_url_prefix, path): +@pytest.mark.parametrize("use_prefix", (True, False)) +def test_base_url_config(app_client_base_url_prefix, path, use_prefix): client = app_client_base_url_prefix - response = client.get("/prefix/" + path.lstrip("/")) + path_to_get = path + if use_prefix: + path_to_get = "/prefix/" + path.lstrip("/") + response = client.get(path_to_get) soup = Soup(response.body, "html.parser") + if path == "/fixtures?sql=select+1": + assert False for el in soup.findAll(["a", "link", "script"]): if "href" in el.attrs: href = el["href"] @@ -1642,11 +1649,12 @@ def test_base_url_config(app_client_base_url_prefix, path): # If this has been made absolute it may start http://localhost/ if href.startswith("http://localhost/"): href = href[len("http://localost/") :] - assert href.startswith("/prefix/"), { + assert href.startswith("/prefix/"), json.dumps({ "path": path, + "path_to_get": path_to_get, "href_or_src": href, "element_parent": str(el.parent), - } + }, indent=4, default=repr)

def test_base_url_affects_metadata_extra_css_urls(app_client_base_url_prefix): ```

Thanks to #1522 I have a live demo that exhibits this bug now: https://apache-proxy-demo.datasette.io/prefix/fixtures/attraction_characteristic

In the meantime I can catch these errors by changing the test to run each path twice, once with and once without the prefix. This should accurately simulate how Apache is working here.

I think what's happening here is Apache is actually making a request to /fixtures rather than making a request to /prefix/fixtures - and Datasette is replying to requests on both the prefixed and the non-prefixed paths.

This is pretty confusing! I think Datasette should ONLY reply to /prefix/fixtures instead and return a 404 for /fixtures - this would make things a whole lot easier to debug.

But shipping that change could break existing deployments. Maybe that should be a breaking change for 1.0.

https://docs.datasette.io/en/stable/deploying.html#apache-proxy-configuration says I should use ProxyPreserveHost on.

Figured it out! The test is not an accurate recreation of what is happening, because it doesn't simulate a request with a path of /fixtures that has been redirected by the proxy to /prefix/fixtures.

Still not clear why the tests pass but the live example fails.

Modified my Dockerfile to do this:

RUN pip install https://github.com/simonw/datasette/archive/ff0dd4da38d48c2fa9250ecf336002c9ed724e36.zip

And now the request in that debug ?_context=1 looks like this: "request": "<asgi.Request method=\"GET\" url=\"http://localhost:9000/fixtures?sql=select+*+from+compound_three_primary_keys+limit+1&_context=1\">" That explains the bug - that request doesn't maintain the original path prefix of http://localhost:5000/foo/bar/fixtures?sql= (also it's been rewritten to localhost:9000 instead of localhost:5000).

In the ?_context= debug view the request looks like this: "request": "<datasette.utils.asgi.Request object at 0x7faf9fe06200>", I'm going to add a repr() to it such that it's a bit more useful.

The implementations of path_with_removed_args and path_with_format:

https://github.com/simonw/datasette/blob/85849935292e500ab7a99f8fe0f9546e903baad3/datasette/utils/init.py#L228-L254

https://github.com/simonw/datasette/blob/85849935292e500ab7a99f8fe0f9546e903baad3/datasette/utils/init.py#L710-L729

Here's the code that generates edit_sql_url correctly: https://github.com/simonw/datasette/blob/85849935292e500ab7a99f8fe0f9546e903baad3/datasette/views/database.py#L416-L420

And here's the code for show_hide_link: https://github.com/simonw/datasette/blob/85849935292e500ab7a99f8fe0f9546e903baad3/datasette/views/database.py#L432-L433

And for url_csv: https://github.com/simonw/datasette/blob/85849935292e500ab7a99f8fe0f9546e903baad3/datasette/views/base.py#L600-L602

The relevant test is this one: https://github.com/simonw/datasette/blob/30255055150d7bc0affc8156adc18295495020ff/tests/test_html.py#L1608-L1649

I modified that test to add "/fixtures/facetable?sql=select+1" as one of the tested paths, and dropped in an assert False to pause it in the debugger: ``` @pytest.mark.parametrize( "path", [ "/", "/fixtures", "/fixtures/compound_three_primary_keys", "/fixtures/compound_three_primary_keys/a,a,a", "/fixtures/paginated_view", "/fixtures/facetable", "/fixtures?sql=select+1", ], ) def test_base_url_config(app_client_base_url_prefix, path): client = app_client_base_url_prefix response = client.get("/prefix/" + path.lstrip("/")) soup = Soup(response.body, "html.parser") if path == "/fixtures?sql=select+1":

      assert False

E assert False BUT... in the debugger: (Pdb) print(soup) ...

This data as json, testall, testnone, testresponse, CSV

`` Those all have the correct prefix! But that's not what I'm seeing in myDockerfile` reproduction of the issue.

Something very weird is going on here.

I added template_debug in the Dockerfile: datasette fixtures.db --setting template_debug 1 --setting base_url "/foo/bar/" -p 9000 &\n\ And then hit http://localhost:5000/foo/bar/fixtures?sql=select+*+from+compound_three_primary_keys+limit+1&_context=1 to view the template context - and it showed the bug, output edited to just show relevant keys:

json { "edit_sql_url": "/foo/bar/fixtures?sql=select+%2A+from+compound_three_primary_keys+limit+1", "settings": { "force_https_urls": false, "template_debug": true, "trace_debug": false, "base_url": "/foo/bar/" }, "show_hide_link": "/fixtures?sql=select+%2A+from+compound_three_primary_keys+limit+1&_context=1&_hide_sql=1", "show_hide_text": "hide", "show_hide_hidden": "", "renderers": { "json": "/fixtures.json?sql=select+*+from+compound_three_primary_keys+limit+1&_context=1" }, "url_csv": "/fixtures.csv?sql=select+*+from+compound_three_primary_keys+limit+1&_context=1&_size=max", "url_csv_path": "/fixtures.csv", "base_url": "/foo/bar/" } This is so strange. edit_sql_url and base_url are correct, but show_hide_link and url_csv and renderers.json are not.

And it's really strange that the bug doesn't show up in the tests.

Bug confirmed:

I now have a Dockerfile in https://github.com/simonw/datasette/issues/1521#issuecomment-974388295 that I can use to run a local Apache 2 with mod_proxy to investigate this class of bugs!

Having a live demo running on Cloud Run that proxies through Apache and uses base_url would be incredibly useful for replicating and debugging this kind of thing. I wonder how hard it is to run Apache and mod_proxy in the same Docker container as Datasette?

base_url has been a source of so many bugs like this! I often find them quite hard to replicate, likely because I haven't made myself a good Apache mod_proxy testing environment yet.