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30 lines
1.2 KiB
Markdown
30 lines
1.2 KiB
Markdown
# Deploy A Review App To A Different Stack
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Heroku has different stacks for deploying apps. As newer versions of Linux
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distros (such as Ubuntu) come out and software packages need patching and
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updating, Heroku releases new stacks. And deprecates older ones.
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Before upgrading a production app to a new stack, you should test it out first.
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The recommended way to test this out is with a Review App.
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If you need to bump the Ruby version or make any other changes, do that first.
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Then add or update your `app.json` file. This is a Heroku-specific file that
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tells Heroku what stack to use when creating a new app or review app.
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```json
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{
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"stack": "heroku-18"
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}
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```
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Let's say my app is currently on the Heroku-16 stack. I can set the `stack` to
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be `heroku-18` in `app.json`. Then I can push up a branch with all these
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changes and turn it into a PR. From the Heroku dashboard, I can click the
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Heroku Button that builds a Review App from the PR.
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Once it it finishes building and deploying, Heroku will give me a custom URL
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for visiting the app so that I can manually evaluate it.
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[source](https://devcenter.heroku.com/articles/upgrading-to-the-latest-stack#testing-an-app-on-a-new-stack)
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