Custom Adapters

Sails makes it fairly easy to write your own database adapter. Custom adapters can be built directly in your app (api/adapters/) or published as NPM packages. Check out Intro to Custom Adapters, the Adapter Interface Reference, and sails-adapter-boilerplate for more information about creating your own adapter.

What goes in a custom adapter?

In Sails, database adapters expose interfaces, which imply a contract to implement certain functionality. This allows us to guarantee conventional usage patterns across multiple models, developers, apps, and even companies, making app code more maintainable, efficient, and reliable. Adapters are primarily useful for integrating with databases, but they can also be used to support any open API or internal/proprietary web service that is purely RESTful.

Not everything fits perfectly into a RESTful/CRUD mold. Sometimes the service you're integrating with has more of an RPC-style interface, with one-off methods. For example, consider an API request to send an email, or to read a remote sensor on a piece of connected hardware. For that, you'll want to write or extend a machinepack. Learn more about machinepacks here.

What kind of things can I do in an adapter?

Adapters are mainly focused on providing model-contextualized CRUD methods. CRUD stands for create, read, update, and delete. In Sails/Waterline, we call these methods create(), find(), update(), and destroy().

For example, a MySQLAdapter implements a create() method which, internally, calls out to a MySQL database using the specified table name and connection informtion and runs an INSERT ... SQL query.

In practice, your adapter can really do anything it likes-- any method you write will be exposed on the raw datastore objects and any models which use them.

Building a custom adapter

Check out the Sails docs, or see config/datastores.js in a new Sails project for information on setting up this adapter in a Sails app.

Running the tests

Configure the interfaces you plan to support (and targeted version of Sails/Waterline) in the adapter's package.json file:

{
  //...
  "sails": {
      "adapter": {
        "sailsVersion": "~0.10.0",
        "implements": [
          "semantic",
          "queryable"
        ]
      }
  }
}

In your adapter's directory, run:

$ npm test

Publish your adapter

You're welcome to write proprietary adapters and use them any way you wish-- these instructions are for releasing an open-source adapter.

1. Create a new public repo and add it as a remote (`git remote add origin [email protected]:yourusername/sails-youradaptername.git)
2. Make sure you attribute yourself as the author and set the license in the package.json to "MIT".
3. Run the tests one last time.
4. Do a pull request to sails-docs adding your adapter's repo.
5. We'll update the documentation with information about your new adapter
6. Let the people of world adore you with lavish praises.
7. Run npm version patch
8. Run git push && git push --tags
9. Run npm publish

Why would I need a custom adapter?

When building a Sails app, the sending or receiving of any asynchronous communication with another piece of hardware can technically be normalized into an adapter. (viz. API integrations)

From Wikipedia: http://en.wikipedia.org/wiki/Create,_read,_update_and_delete

Although a relational database provides a common persistence layer in software applications, numerous other persistence layers exist. CRUD functionality can be implemented with an object database, an XML database, flat text files, custom file formats, tape, or card, for example.

In other words, Waterline is not necessarily just an ORM for your database. It is a purpose-agnostic, open standard and toolset for integrating with all kinds of RESTful services, datasources, and devices, whether it's LDAP, Neo4J, or a lamp.

But remember: only use Waterline adapters for communicating with databases and APIs that support a "create", "read", "update", and "destroy" interface. Not everything fits into that mold, and there are better, more generic ways to address those other use cases.

Why should I build a custom adapter?

To recap, writing your API integrations as adapters is easier, takes less time, and absorbs a considerable amount of risk, since you get the advantage of a standardized set of conventions, a documented API, and a built-in community of other developers who have gone through the same process. Best of all, you (and your team) can reuse the adapter in other projects, speeding up development and saving time and money.

Finally, if you choose to release your adapter as open-source, you provide a tremendous boon to our little framework and our budding Sails.js ecosystem. Even if it's not via Sails, I encourage you to give back to the OSS community, even if you've never forked a repo before-- don't be intimidated, it's not that bad!

The more high-quality adapters the Sails community collectively releases as open-source, the less repetitive work we all have to do when we integrate with various databases and services. Our vision is to make building server-side apps more fun and less repetitive for everyone, and that happens one community adapter (or machinepack/driver/generator/view engine/etc.) at a time.

What is an adapter interface?

The functionality of database adapters is as varied as the services they connect. That said, there is a standard library of methods, and a support matrix you should be aware of. Adapters may implement some, all, or none of the interfaces below, but rest assured that if an adapter implements one method in an interface, it should implement all of them. This is not always the case due to limitations and/or incomplete implementations, but at the very least, a descriptive error message should be used to keep developers informed of what's supported and what's not.

For more information, check out the Sails docs, and specifically the adapter interface reference.

Are there examples I can look at?

If you're looking for some inspiration, a good place to start is with the core adapters. Take a look at MySQL, PostgreSQL, MongoDB, Redis, local disk, or local memory.

Where do I get help?

An active community of Sails and Waterline users exists on GitHub, Stack Overflow, Google groups, IRC, Gitter, and more. See the Support page for a list of recommendations.

If you have an unanswered question that isn't covered here, and that you feel would add value for the community, please feel free to send a PR adding it to this section of the docs.