Written on 21 Dec 2020

Configuring Datasette timeout options on Heroku

It isn't hard to configure, but I spent more than 15 minutes searching and fiddling so here is the blog post I wish I had come across.

Datasette is great software and is easy to use. It lets me can focus on building up a database and gives me a searchable web UI and an API for my data. But the defaults aren't always sufficient for deploying to Heroku. For example, I ran into an SQL timeout error pretty quickly.

SQL timeout error served by datasette on Heroku
The error I saw on Heroku

I'm using datasette for the California municipal campaign finance project and saw the timeout errors when I was just sorting some columns. So I wanted to up the timeout limit from the default of 1 second to 4 seconds.

Why 4 seconds? 🤷‍♂️ It's more than 1 and less than a lot?

The documentation is very clear about how to do this when running datasette locally:

datasette mydatabase.db --setting sql_time_limit_ms 4000

The documentation is less clear about how you might combine that setting with the datasette publish command so that the timeout takes effect on Heroku. Turns out the winning combination is the --extra-options flag with a quoted --setting flag.

I successfully increased the timeout on Heroku with:

datasette publish heroku \
  --name $HEROKU_APP_NAME \
  --extra-options \"--setting sql_time_limit_ms 4000\" \