Heroku CI In-Dyno Databases

Last updated 06 March 2018

In-Dyno Databases

In-Dyno databases are databases that run inside your test-run’s dyno. These databases differ from the more traditional Heroku addons like Heroku Postgres and Heroku Redis in a few notable ways:

• Database queries do not pass over the network, and, as a result, finish in a more consistent and fast speed.
• Many of the restrictions that apply to external addons (like row limits, connection limits, feature enablement, and the ability to create more database) do not apply.
• The data is ephemeral, meaning it is not persisted, backed up, or available outside of the dyno in any way.

The primary drawback to this type of database is it’s ephemerality; as such, this type of database would not be appropriate for production use. However, because test runs are ephemeral themselves, the advantages of greater flexibility and speed make it a great improvement for your CI workflow.

Usage

Before you can use In-Dyno databases, you need to specify a buildpack in your app.json that reflects the language you’re testing. For example:

"buildpacks": [
  { "url": "heroku/ruby" }
]

You can use In-Dyno databases for your Heroku CI test runs by using an in-dyno plan. You may specify this in your app.json. For example:

{
  "environments": {
    "test": {
      "addons": ["heroku-postgresql:in-dyno", "heroku-redis:in-dyno"]
    }
  }
}

When a test run begins, you can use the database as normal via DATABASE_URL or REDIS_URL as appropriate. These urls will point to your locally installed database.

Restrictions

• In-Dyno databases only work in Heroku CI. They will not be provisioned for any other type of app (such as Review Apps or Heroku Button Apps).
• Currently, in-dyno plans are only supported for the heroku-redis and heroku-postgresql addons.