XPike.Configuration

This library provides a standardized surface for configuration within XPike.

Out-of-box support:

• System environment variables
• Web.config / App.config
• appsettings.json
• In-memory/hardcoded key-value pair
• Microsoft Extensions / .NET Core IConfiguration
• AWS Simple Configuration Service
• Azure Application Configuration Service

Additionally, support for IConfiguration is bi-directional by default - both XPike and Microsoft libraries will have access to the combined result of providers from both systems.

Use cases:

• Provides bootstrap-time configuration in Program.cs/Startup.cs/Global.asax
• Provides configuration for most XPike functionality
• A fast, lightweight option for application-level configuration

Because XPike Configuration is available prior to creating a Dependency Injection container, XPike Configuration Providers can't require any injected dependencies.

Similar to ASP.NET Middleware, the default implementation of the XPike Configuration Service has an extensible async pipeline at its core. As with the Provider list, this can be modified at runtime, allowing for capabilities to be added after Dependency Injection is available.

Available pipeline enhancements:

• XPike Caching support
  • Uses an n-tier cache (eg: in-memory + redis) with distributed invalidation to allow nodes to keep their settings highly synchronized while reducing the burden of using a remote configuration source such as AWS or Azure.
• XPike Multi-Tenant support
  • Allows for per-tenant settings overrides to support multi-tenancy throughout XPike as well as within application-level settings.

Design Notes:

The root of the system is the Configuration Service:

. This has an async pipeline with a list of pipeline. Pipeline components are executed starting with the most-recently-added component and ending with an internal implementation.
Providers are wrapped by the Configuration Service which scans them in reverse order, returning the first value it finds. While Providers can be used directly, the Configuration Service should be your go-to (and it is compatible with .NET Core IConfiguration).

Though the Configuration Service does not rely on DI, it is intended to be registered with the container along with any Providers. This is because XPike Settings (which adds capabilities such as caching and refresh - similar to .NET Core IOptions) relys on the Configuration Service as its default Settings Provider.

XPike Configuration can also be extended/enhanced by adding to its async pipeline. Currently, there are pipeline components to add XPike Caching and XPike Multi-Tenant support.

While XPike Configuration offers POCO deserialization, it is recommended to use the XPike.Settings Package to retrieve application settings. XPike Settings uses XPike Configuration as one of its sources, but you can also add additional providers which can have injected dependencies.

Setup

ASP.NET Core

.NET Framework

Exported Services

• IConfigurationService
  => ConfigurationService
  This is the primary interface that should be injected into business logic libraries. Allows the use of multiple IConfigurationProvider implementations, with a tiered/failover approach.

• IEnvironmentConfigurationProvider
  => EnvironmentConfigurationProvider
  Acquires settings from environment variables using System.Environment.

  Note: This is added to the collection of providers by default when using this library's Dependency Package. To remove it, call IDependencyCollection.ResetCollection<IConfigurationProvider>() and then register your desired providers.

• IMemoryConfigurationProvider
  => MemoryConfigurationProvider
  Acquires settings from a pre-defined IDictionary<string, string>.

• INullConfigurationProvider
  => NullConfigurationProvider
  For testing purposes. Returns null, or any specified default value (when applicable).

Interfaces

IConfigurationProvider

NOTE: Implementations of this interface must be registered using Collection Registration via IDependencyContainer.AddSingleton<TService>().

• string GetValue(string key)
  Throws an InvalidConfigurationException if the specified key is not found.

• string GetValueOrDefault(string key, string defaultValue = null)
  Returns the specified default value if the key is not found.

• T GetValue<T>(string key)
  For intrinsic data types such as int and bool, uses System.Convert to cast the value.
  For other data types, uses JsonConvert to deserialize from a JSON string. This may vary by Provider, however.
  Throws an InvalidConfigurationException if the specified key is not found.

• **T GetValue<T>(string key, T defaultValue = default)
  Same as above, but returns the specified default value if the key is not found.

IConfigurationLoader

Some Providers may choose to implement this interface, which enables bulk-loading of configuration.

• IDictionary<string, string> Load()
  Returns the complete set of key-value pairs that a Provider can access.

This is intended for compatibility with ASP.NET Core, so that Microsoft.Extensions.Configuration can use XPike Configuration as its source for IOptions<>.

xPike offers a similar ISettings<> which will work with any and all Configuration Providers, though all of the implementations xPike provides by default are .NET Core compatible.

IConfigurationService

This is the composite service that should be used to retrieve configuration.

This interface implements both IConfigurationProvider and IConfigurationLoader, proxying to the underlying Providers and selecting the value from the highest-priority provider.

Note that calls to its IConfigurationLoader.Load() method will only return values from Providers that also implement IConfigurationLoader.

Base Classes

ConfigurationProviderBase

An abstract base class which adds support for deserialization and error handling, reducing the surface area that each Provider needs to implement.

At a minimum, the GetValueOrDefault(string key, string defaultValue = null) must be overridden to implement a new Provider.

Exceptions

InvalidConfigurationException

Thrown when a setting can not be found. An informational message will be applied. It may also wrap an underlying Exception when present.

• string Key { get; }
  Specifies the Configuration Key which was not able to be found.

Dependencies

• XPike.IoC

Building and Testing

Building from source and running unit tests requires a Windows machine with:

• .Net Core 3.0 SDK
• .Net Framework 4.6.1 Developer Pack

Issues

Issues are tracked on GitHub. Anyone is welcome to file a bug, an enhancement request, or ask a general question. We ask that bug reports include:

1. A detailed description of the problem
2. Steps to reproduce
3. Expected results
4. Actual results
5. Version of the package xPike
6. Version of the .Net runtime

Contributing

See our contributing guidelines in our documentation for information on how to contribute to xPike.

License

xPike is licensed under the MIT License.