aka Ubuntu 16.04 -> Ubuntu 18.04 https://devcenter.heroku.com/changelog-items/1453 https://devcenter.heroku.com/articles/heroku-18-stack https://devcenter.heroku.com/articles/upgrading-to-the-latest-stack

This is blocked on: https://github.com/heroku/heroku-buildpack-python/issues/735

Heroku have intentionally not made Python 2.7 available on the Heroku-18 stack, since the Python 2 EOL will be before the Ubuntu 18.04 EOL. As such, upgrading stack will need to wait for our switch to Python 3 in bug 1330474.

Heroku have decided to support Python 2.7 on Heroku-18 after all (https://devcenter.heroku.com/changelog-items/1472) meaning this bug is no longer blocked on the switch to Python 3.

Commit pushed to master at https://github.com/mozilla/treeherder https://github.com/mozilla/treeherder/commit/b7cf0c28cecd9e0ef0da6fe7f00f87ca1b7fb0f9 Bug 1478059 - Vagrant: Switch from Ubuntu 16.04 to 18.04 (#4064) In addition: * The minimum Vagrant version has been bumped, to pick up fixes for newer Ubuntu versions. * The Hyper-V config has been removed, since it hasn't worked for a while (issues with networking etc). * Any provision clean-up steps that are redundant (given that we know people will be starting with a fresh VM) have been removed. * The latest version of pip is now used.

I set the stack on prototype to Heroku-18 and the builds were successful, so I've also changed over stage. If that looks good after a day or so I'll switch over prod too.

I've set the stack on prod to heroku-18; the next deploy will make this take effect.

Prod deployed this morning which completed the switch to Heroku-18. Interestingly the memory usage on the web workers appears to have dropped by 20% compared to Heroku-16 (even comparing to after a restart on Heroku-16), which helps with the occasional exceeding limit/swapping we were seeing.