Simon Willison’s Weblog

asgi-replay. As part of submitting LLM to Homebrew core I needed an automated test that demonstrated that the tool was working—but I couldn’t test against the live OpenAI API because I didn’t want to have to reveal my API token as part of the test. I solved this by creating a dummy HTTP endpoint that simulates a hit to the OpenAI API, then configuring the Homebrew test to hit that instead. As part of THAT I ended up building this tiny tool which uses my asgi-proxy-lib package to intercept and log the details of hits made to a service, then provides a mechanism to replay that traffic. # 24th July 2023, 7:51 pm

Writing a chat application in Django 4.2 using async StreamingHttpResponse, Server-Sent Events and PostgreSQL LISTEN/NOTIFY (via) Excellent tutorial by Víðir Valberg Guðmundsson on implementing chat with server-sent events using the newly async-capable StreamingHttpResponse from Django 4.2x.

He uses PostgreSQL’a LISTEN/NOTIFY mechanism which can be used asynchronously in psycopg3—at the cost of a separate connection per user of the chat.

The article also covers how to use the Last-Event-ID header to implement reconnections in server-sent events, transmitting any events that may have been missed during the time that the connection was dropped. # 19th May 2023, 3:42 pm

datasette-granian (via) Granian is a new Python web server—similar to Gunicorn—written in Rust. I built a small plugin that adds a “datasette granian” command starting a Granian server that serves Datasette’s ASGI application, using the same pattern as my existing datasette-gunicorn plugin. # 20th January 2023, 2:12 am

Deploying Python web apps as AWS Lambda functions. After literally years of failed half-hearted attempts, I finally managed to deploy an ASGI Python web application (Datasette) to an AWS Lambda function! Here are my extensive notes. # 19th September 2022, 4:05 am

Async Support—HTTPX (via) HTTPX is the new async-friendly HTTP library for Python spearheaded by Tom Christie. It works in both async and non-async mode with an API very similar to requests. The async support is particularly interesting—it’s a really clean API, and now that Jupyter supports top-level await you can run ’(await httpx.AsyncClient().get(url)).text’ directly in a cell and get back the response. Most excitingly the library lets you pass an ASGI app directly to the client and then perform requests against it—ideal for unit tests. # 10th January 2020, 4:49 am

Datasette 0.31. Released today: this version adds compatibility with Python 3.8 and breaks compatibility with Python 3.5. Since Glitch support Python 3.7.3 now I decided I could finally give up on 3.5. This means Datasette can use f-strings now, but more importantly it opens up the opportunity to start taking advantage of Starlette, which makes all kinds of interesting new ASGI-based plugins much easier to build. # 12th November 2019, 6:11 am

datasette-cors (via) My other Datasette ASGI plugin: this one wraps my asgi-cors project and lets you configure CORS access from a list of domains (or a set of domain wildcards) so you can make JavaScript calls to a Datasette instance from a specific set of other hosts. # 8th July 2019, 4:30 am

datasette-auth-github (via) My first big ASGI plugin for Datasette: datasette-auth-github adds the ability to require users to authenticate against the GitHub OAuth API. You can whitelist specific users, or you can restrict access to members of specific GitHub organizations or teams. While it’s structured as a Datasette plugin it also includes ASGI middleware which can be applied to any ASGI application. # 8th July 2019, 4:28 am

asgi-cors (via) I’ve been trying out the new ASGI 3.0 spec and I just released my first piece of ASGI middleware: asgi-cors, which lets you wrap an ASGI application with Access-Control-Allow-Origin CORS headers (either “*” or dynamic headers based on an origin whitelist). # 7th May 2019, 12:12 am

Hello world for ASGI running on Glitch (via) I’m continuing to experiment with Python 3 running on Glitch. This evening on my walk home from work I built this “hello world” demo on my phone, partly to see if Glitch was a workable mobile development environment—it passed with flying colours! The demo is a simple hello world implemented using the new ASGI 3.0 specification, running on the daphne reference server. Click the “via” link for my accompanying thread on Twitter, which includes a short screencast (also recorded on my phone) showing Glitch in action. # 26th April 2019, 5:06 am