google-nomulus/docs/configuration.md

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 registry_tool commands without having to deploy a new version.

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" documentation for more details on environments as used in the domain registry.

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. The main files of note that come pre-configured along with the domain registry 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

There are two different mechanisms by which global configuration is managed: RegistryConfig (the old way) and ConfigModule (the new way). Ideally there would just be one, but the required code cleanup that hasn't been completed yet. If you are adding new options, prefer adding them to ConfigModule.

RegistryConfig is an interface, of which you write an implementing class containing the configuration values. RegistryConfigLoader is the class that provides the instance of RegistryConfig, and defaults to returning ProductionRegistryConfigExample. In order to create a configuration specific to your registry, we recommend copying the ProductionRegistryConfigExample class to a new class that will not be shared publicly, setting the com.google.domain.registry.config system property in appengine-web.xml to the fully qualified class name of that new class so that RegistryConfigLoader will load it instead, and then editing said new class to add your specific configuration options.

The RegistryConfig class has documentation on all of the methods that should be sufficient to explain what each option is, and ProductionRegistryConfigExample provides an example value for each one. Some example configuration options in this interface include the App Engine project ID, the number of days to retain commit logs, the names of various Cloud Storage bucket names, and URLs for some required services both external and internal.

ConfigModule is a Dagger module that provides injectable configuration options (some of which come from RegistryConfig above, but most of which do not). This is preferred over RegistryConfig for new configuration options because being able to inject configuration options is a nicer pattern that makes for cleaner code. 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.

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 update_tld command in registry_tool is used to set all of these options. See the "Registry tool" documentation 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.