add content/posts/2025-03-30-jupyterlab-reverse-proxying-in-apache.md

1 files changed, 80 insertions, 0 deletions

diff --git a/content/posts/2025-03-30-jupyterlab-reverse-proxying-in-apache.md b/content/posts/2025-03-30-jupyterlab-reverse-proxying-in-apache.md
new file mode 100644
index 0000000..b611101
--- /dev/null
+++ b/content/posts/2025-03-30-jupyterlab-reverse-proxying-in-apache.md
@@ -0,0 +1,80 @@
+---
+slug: jupyterlab-reverse-proxying-in-apache
+title: "JupyterLab Reverse Proxying in Apache"
+date: "2025-03-30T22:57:18-04:00"
+draft: true
+---
+
+I've been using the [SageMath][] kernel in [JupyterLab][] quite a bit
+lately.  I wanted to [reverse proxy][] through an [Apache][] [vhost][]
+to [JupyterLab][].  The documentation to do this is surprisingly
+elusive.
+
+Here is a working example:
+
+```apache
+<VirtualHost *:443>
+  ServerName sage.example.com
+
+  # proxy http and websocket to http://localhost:1980/
+  # note: in apache 2.4.47+, use upgrade=websocket to proxy websocket
+  ProxyPass "/" http://localhost:1980/ upgrade=websocket
+  ProxyPassReverse "/" http://localhost:1980/ upgrade=websocket
+
+  # preserve Host header in proxied requests
+  ProxyPreserveHost on
+
+  # ... common vhost configuration elided
+</VirtualHost>
+```
+&nbsp;
+
+Notes:
+
+1. Add `upgrade=websocket` to [ProxyPass][] and [ProxyPassReverse][].
+Needed to proxy [WebSocket][] connections in [Apache][] 2.4.47+.  See
+the [Protocol Upgrade note][protocol-upgrade] in the [mod\_proxy
+documentation][mod_proxy] for additional details.
+2. Enable [ProxyPreserveHost][].  This preserves the `Host` header in
+proxied requests and it is needed to prevent cryptic server-side origin
+errors.
+
+The [JupyterLab][] instance is running in a [Podman][] [container][],
+like so:
+
+```sh
+podman run -d -p 1980:8888 \
+  -v sage:/home/sage/work \
+  --restart=on-failure \
+  --name sage \
+  docker.io/sagemath/sagemath sage-jupyter
+```
+
+[jupyterlab]: https://jupyter.org/
+  "JupyterLab"
+[apache]: https://apache.org/
+  "Apache web server"
+[reverse proxy]: https://en.wikipedia.org/wiki/Reverse_proxy
+  "Reverse proxy (Wikipedia)"
+[vhost]: https://httpd.apache.org/docs/current/vhosts/
+  "Apache virtual host (apache.org)"
+[protocol-upgrade]: https://httpd.apache.org/docs/2.4/mod/mod_proxy.html#wsupgrade
+  "Protocol Upgrade note in mod_proxy documentation."
+[proxypass]: https://httpd.apache.org/docs/2.4/mod/mod_proxy.html#proxypass
+  "ProxyPass directive (apache.org)"
+[proxypassreverse]: https://httpd.apache.org/docs/2.4/mod/mod_proxy.html#proxypassreverse
+  "ProxyPassReverse directive (apache.org)"
+[proxypreservehost]: https://httpd.apache.org/docs/2.4/mod/mod_proxy.html#proxypreservehost
+  "ProxyPreserveHost directive (apache.org)"
+[websocket]: https://en.wikipedia.org/wiki/WebSocket
+  "WebSocket (Wikipedia)"
+[sagemath]: https://sagemath.org/
+  "SageMath"
+[mod_proxy]: https://httpd.apache.org/docs/2.4/mod/mod_proxy.html
+  "Apache proxy module."
+[mod_proxy_http]: https://httpd.apache.org/docs/2.4/mod/mod_proxy_http.html
+  "Apache module to proxy HTTP requests."
+[podman]: https://en.wikipedia.org/wiki/Podman
+  "Podman container manager (Wikipedia)"
+[container]: https://en.wikipedia.org/wiki/Containerization_(computing)
+  "Operating system level virtualization (Wikipedia)"