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51 lines
1.6 KiB
Markdown
51 lines
1.6 KiB
Markdown
## Database migrations
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The history service uses knex to manage PostgreSQL migrations.
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To create a new migrations, run:
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```
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npx knex migrate:make migration_name
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```
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To apply migrations, run:
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```
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npx knex migrate:latest
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```
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For more information, consult the [knex migrations
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guide](https://knexjs.org/guide/migrations.html#migration-cli).
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## Global blobs
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Global blobs are blobs that are shared between projects. The list of global
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blobs is stored in the projectHistoryGlobalBlobs Mongo collection and is read
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when the service starts. Changing the list of global blobs needs to be done
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carefully.
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### Adding a blob to the global blobs list
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If we identify a blob that appears in many projects, we might want to move that
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blob to the global blobs list.
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1. Add a record for the blob to the projectHistoryGlobalBlobs collection.
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2. Restart the history service.
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3. Delete any corresponding project blobs.
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### Removing a blob from the global blobs list
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Removing a blob from the global blobs list is trickier. As soon as the global
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blob is made unavailable, every project that needs the blob will have to get
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its own copy. To avoid disruptions, follow these steps:
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1. In the projectHistoryGlobalBlobs collection, set the `demoted` property to
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`false` on the global blob to remove. This will make the history system
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write new instances of this blob to project blobs, but still read from the
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global blob.
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2. Restart the history service.
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3. Copy the blob to all projects that need it.
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4. Remove the blob from the projectHistoryGlobalBlobs collection.
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5. Restart the history service.
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