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ConfigService Notes

ED: this page can probably be deleted. Everything worth saving has been moved to ConfigService.

Introduction

A configuration service may be the solution if you need more flexibility than the more traditional file based approaches. Such a service makes it possible to

  • use different transport protocols and formats.
  • share properties between applications. (for example ensure that two applications use the same url for a JMS-server.)
  • apply rules and other business logic before selecting which properties to return.
  • let the user setup a monolithic configuration and let the service extract the relevant configuration for a specific application and return a transformed version of the monolithic configuration.
  • set up a GUI for changing the properties.
  • switch implementation without changing the clients, as long as the interface is kept stable. See for example Evolving Service Endpoint for more information.
  • add cache support
    • merge is a possible issue, but can be handled in the service

The list of possibilities above is not meant as a complete list in any way. The idea was just to indicate that introducing a configuration service gives you a lot more flexibility.

A wide range of technology can be used to implement such a service. For example JMX RPC:

Design

Integration with applications

We have identified three options for integration with applications

  • Wire it up with Spring (spring modules + commons-configuration seems the easiest implementation)
  • Fetch programmatically
  • Use a bootstrap class to fetch the configuration before starting the application using System.exec on the original main class.
The configuration functionality

TODO: link to multi-dimensional configuration system (formerly known as staged-spring).

Versioning

We can achieve traceability and versioning by indexing the configuration. Using Lucene as backend should achieve this goal and will additionally give us advanced search functionality for "free".

Client to change configuration

Constretto multi-dimensional configuration system (formerly known as staged-spring).

The visualizer was neat. :)