I Broke the Refresh Button: Dealing with a Rogue Service Worker

#serviceworker #javascript #webdev

I was quite happy to launch a new version of a website last week. I was less happy when, come Monday, people were still seeing the old version. The standard "have you tried refreshing" had no effect: no matter home many times people refreshed, the old content would keep coming back. This was some aggressive caching!

The culprit was an old service-worker.js file! The old site had been built with create-react-app, which included service worker registration by default and which I hadn't paid much attention to. The new site was built with Gatsby, which doesn't include one by default.

Service workers can help you to cache your site/PWA so that it still functions while offline. Typically, a service worker will check for a new version of itself whenever you visit the associated site after a 24 hour period. But when the old service worker checked for an update, it got a 404 response and defaulted to staying alive and serving cached content no matter what.

To get clients to stop relying on the old service worker, I had to add a new "updated" service-worker.js to the site's root (where it expected to find it).

The new service worker, in its entirety:

self.addEventListener('install', () => {
  self.skipWaiting();
});

All this does is tell the browser: "Hey, I'm the new service worker, chuck out that old service worker, and, uh, that's it, we're done here."

Since this particular site never really needed a service worker in the first place, I'm happy with this no-op service worker as a quick and dirty solution. After clients grab this to replace the last service worker, a simple refresh will once again allow their browser to actually hit the Internet to grab things, and not just rely on a very stale cache.

Thanks to Jeff Posnick via StackOverflow for this simple solution! I've got a lot to learn about how service workers function, and a newfound respect for what happens if you're using them without really understanding them