Allow for re-installation of a custom configuration

[seppyk]

This is an improvement request.

Currently, one can create a custom configuration and install it via the ConfigurationManager:

ConfigurationManager.install(abstractConfiguration);

One cannot re-install a configuration due to the check in DynamicPropertyFactory

if (ConfigurationManager.isConfigurationInstalled() && config != ConfigurationManager.instance) {
  throw new IllegalStateException("ConfigurationManager is already initialized with configuration " + ConfigurationManager.getConfigInstance());
}

It would be useful to be able to re-define the installed configuration dynamically. This also causes some conflicts in a Spring test environment as the application context can reload during testing with a different configuration that can never be re-installed.

[howardyuan]

@seppyk re-install a configuration should be feasible. Current code base already has sort of supported installing a new customer config. Right now, it just allows for one time installation as you pointed out. But mechanism of installing a new configuration is already there. I'll probably keep the current "install" behavior the same and introduce a re-install interface to explicitly telling Archaius to expect new custom configuration.

[gorzell]

@howardyuan it may be to big a change for this issue, but I think we should look at moving away from a model that requires a single configuration per JVM. Instead I think the ConfigManager should operate on named configuration hierarchy, with perhaps a default name for the base configuration.

This would also help us start to pull apart the DynamicProperty APIs and utilities from common-configuration. Which I think will help with a few other issues that people are having.

[chandrapersonal]

Any updates on this. re-install a configuration should be feasible. i am useing ETCD as source in archaius to dynamically update the properties in spring. but my etcd server connection is timeing out for 5 min. So i have to re-install configuration source. Is there any other way to configure ETCD more than one time.

[howardyuan]

@chandrapersonal Can you clarify your problem? Are you saying that your etcd source is no longer available and you want to use a different source? If so, I think you should be able to create a new polling source instead of re-install the configuration manager as the #113 issue was referring to.