63 lines
2.5 KiB
Markdown
63 lines
2.5 KiB
Markdown
---
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title: Data Update Scripts
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---
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## What are Data Update Scripts?
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Data Update Scripts were introduced in
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[this PR](https://github.com/thepracticaldev/dev.to/pull/6025) and allow us to
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run any data updates we might need. For example, if we added a column to the
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database and then wanted to backfill that column with data, rather than going
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and manually doing it in a console, we would use a DataUpdateScript. Another
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example might be adding a new attribute to Elasticsearch. We could then use a
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DataUpdateScript to reindex all of our models.
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## How it works
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First off, we added a
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[DataUpdateScript model](https://github.com/thepracticaldev/dev.to/blob/master/app/models/data_update_script.rb)
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to Rails and a corresponding database table. This table is what we use to keep
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track of what scripts have been run and which ones have not/still need to be.
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To create a script you can use our custom Rails generator:
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```
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rails generate data_update BackfillColumnForArticles
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```
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This will create a simple Ruby class like below and all you have to do is fill
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in the code it will run.
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```ruby
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module DataUpdateScripts
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class BackfillColumnForArticles
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def run
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# Place your data update logic here
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# Make sure your code is idempotent and can be run safely
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# multiple times at any time
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end
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end
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end
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```
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Once your script is in place then you can either run `rails data_updates:run`
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manually or you can let our setup and update scripts handle it. In our local
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[bin/setup](https://github.com/thepracticaldev/dev.to/blob/master/bin/setup#L36)
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and
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[bin/update](https://github.com/thepracticaldev/dev.to/blob/master/bin/update#L26)
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scripts you will see we have added an additional task to "Update Data". This
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kicks off the rake task `data_updates:run` for you.
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The rake task itself will check the `lib/data_update_scripts` folder to see if
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there are any new scripts that need to be run. It does this by reading all of
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the files and then checking to see if they have a corresponding database entry.
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If they do not, then we create a new one and run the script. If a database entry
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already exists and it indicates the script has been run, then we skip that
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script.
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## In production
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DataUpdateScripts are also run automatically when a production deploy goes out.
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However, to ensure the new code they need to use has been deployed we use a
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[`DataUpdateWorker`](https://github.com/thepracticaldev/dev.to/blob/master/app/workers/data_update_worker.rb)
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via Sidekiq and set it to run 10 minutes after the deploy script has completed.
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