# Configuration

There are multiple different kinds of configuration that go into getting a
working registry system up and running. Broadly speaking, configuration works in
two ways -- globally, for the entire sytem, and per-TLD. Global configuration is
managed by editing code and deploying a new version, whereas per-TLD
configuration is data that lives in Datastore in `Registry` entities, and is
updated by running `nomulus` commands without having to deploy a new version.

## Initial configuration

Here's a checklist of things that need to be configured upon initial
installation of the project:

*   Create Google Cloud Storage buckets (see the [App Engine architecture
    guide](./app-engine-architecture.md)).
*   Modify `ConfigModule.java` and set project-specific settings such as product
    name (see below).
*   Copy and edit `ProductionRegistryConfigExample.java` with your
    project-specific settings (see below).

## Environments

Before getting into the details of configuration, it's important to note that a
lot of configuration is environment-dependent. It is common to see `switch`
statements that operate on the current `RegistryEnvironment`, and return
different values for different environments. This is especially pronounced in
the `UNITTEST` and `LOCAL` environments, which don't run on App Engine at all.
As an example, some timeouts may be long in production and short in unit tests.

See the [App Engine architecture](./app-engine-architecture.md) documentation
for more details on environments as used by Nomulus.

## App Engine configuration

App Engine configuration isn't covered in depth in this document as it is
thoroughly documented in the [App Engine configuration docs][app-engine-config].
The main files of note that come pre-configured in Nomulus are:

*   `cron.xml` -- Configuration of cronjobs
*   `web.xml` -- Configuration of URL paths on the webserver
*   `appengine-web.xml` -- Overall App Engine settings including number and type
    of instances
*   `datastore-indexes.xml` -- Configuration of entity indexes in Datastore
*   `queue.xml` -- Configuration of App Engine task queues
*   `application.xml` -- Configuration of the application name and its services

Cron, web, and queue are covered in more detail in the "App Engine architecture"
doc, and the rest are covered in the general App Engine documentation.

If you are not writing new code to implement custom features, is unlikely that
you will need to make any modifications beyond simple changes to
`application.xml` and `appengine-web.xml`. If you are writing new features, it's
likely you'll need to add cronjobs, URL paths, Datastore indexes, and task
queues, and thus edit those associated XML files.

## Global configuration

Global configuration is managed through **`ConfigModule`**, which is a Dagger
module that provides injectable configuration options. Some configuration
options that can be changed in this class include timeout lengths and buffer
sizes for various tasks, email addresses and URLs to use for various services,
more Cloud Storage bucket names, and WHOIS disclaimer text. Currently, in order
to configure custom configuration, you need to copy `ConfigModule`, make changes
to it, and include your new version instead of the default one in all Dagger
components. In the near future, configuration via YAML files will be supported,
after which point changes to `ConfigModule` will not be required at all.

## Sensitive global configuration

Some configuration values, such as PGP private keys, are so sensitive that they
should not be written in code as per the configuration methods above, as that
would pose too high a risk of them accidentally being leaked, e.g. in a source
control mishap. We use a secret store to persist these values in a secure
manner, and abstract access to them using the `Keyring` interface.

The `Keyring` interface contains methods for all sensitive configuration values,
which are primarily credentials used to access various ICANN and ICANN-
affiliated services (such as RDE). These values are only needed for real
production registries and PDT environments. If you are just playing around with
the platform at first, it is OK to put off defining these values until
necessary. To that end, a `DummyKeyringModule` is included that simply provides
an `InMemoryKeyring` populated with dummy values for all secret keys. This
allows the codebase to compile and run, but of course any actions that attempt
to connect to external services will fail because none of the keys are real.

To configure a production registry system, you will need to write a replacement
module for `DummyKeyringModule` that loads the credentials in a secure way, and
provides them using either an instance of `InMemoryKeyring` or your own custom
implementation of `Keyring`. You then need to replace all usages of
`DummyKeyringModule` with your own module in all of the per-service components
in which it is referenced. The functions in `PgpHelper` will likely prove useful
for loading keys stored in PGP format into the PGP key classes that you'll need
to provide from `Keyring`, and you can see examples of them in action in
`DummyKeyringModule`.

## Per-TLD configuration

`Registry` entities, which are persisted to Datastore, are used for per-TLD
configuration. They contain any kind of configuration that is specific to a TLD,
such as the create/renew price of a domain name, the pricing engine
implementation, the DNS writer implementation, whether escrow exports are
enabled, the default currency, the reserved label lists, and more. The `nomulus
update_tld` command is used to set all of these options. See the [admin tool
documentation](./admin-tool.md) for more information, as well as the
command-line help for the `update_tld` command. Unlike global configuration
above, per-TLD configuration options are stored as data in the running system,
and thus do not require code pushes to update.

[app-engine-config]: https://cloud.google.com/appengine/docs/java/configuration-files