In for the long poll
Launchpad has quite a few background tasks that update things outside of your browser request, and the only way you know that they finished is to reload a page to see if it changes.
Updating the preview diff on a merge proposal is one example.
At our Launchpad sprint in Dublin a couple of weeks ago, we added a so-called “long poll” where the browser opens a long-running connection using XHR (a background Javascript connection) to a new piece of infrastructure called the “long poll server”
This server is something that the Landscape team originally wrote and we’ve now open-sourced it so we can use it in Launchpad. The server connects to a RabbitMQ instance and relays information back to the browser when the background task completes so that the user doesn’t need to keep reloading the page – the page will automatically update thanks to the magic of Javascript.
The proof-of-concept is done but we now need to make it work in our production environment, which means making it more reliable, configuring the deployment and add some stats collection so we can see how it behaves. We’ll start off by only letting a small subset of people use it and grow it over time until we consider it stable enough for all users.
Photo by Jay Gooby. Licence: CC BY 2.0
