External Configuration Store Pattern

[satishnaidu]

Description:
The External Configuration Store design pattern involves storing configuration settings outside of the application, which allows for the modification of these settings without the need to redeploy the application. This pattern is particularly useful for cloud-based applications where environments can change dynamically, and configurations need to be updated frequently.

Main elements of External Configuration Store pattern:

1. Configuration Source: A centralized external source where configurations are stored. This can be a database, a cloud-based service, or a configuration server.
2. Configuration Retrieval: Mechanism to fetch the configuration from the external store. This can be done at application startup and periodically at runtime to ensure the latest configuration is always applied.
3. Configuration Management: Tools and interfaces to manage, update, and monitor the configurations in the external store.
4. Fallback Mechanism: In case the external configuration source is unavailable, the application should have a fallback mechanism, such as default settings or cached configurations.

References:

• External Configuration Store - Microsoft Docs
• 12 Factor App - Store config in the environment
• GitHub Contribution Guidelines

Acceptance Criteria:

1. Implement a mechanism to retrieve configurations from an external store (e.g., AWS SSM, Consul, etc.) and apply them to the application at startup and during runtime.
2. Create a configuration management interface to allow for easy updates and monitoring of configuration settings.
3. Ensure a fallback mechanism is in place to handle scenarios where the external configuration store is unreachable. This should include default settings or cached configurations.

[npathai]

Just for reference https://msdn.microsoft.com/en-us/library/dn589803.aspx
@satishnaidu Thank you for showing interest in contributing. Yes you may go ahead. We welcome contributions 👍 . But I think we need to discuss how are we going to implement cloud design patterns. Put forward your thoughts @iluwatar @satishnaidu
I don't have any experience related to cloud technologies.

[npathai]

@satishnaidu We have how to contribute guidelines in README.md

[satishnaidu]

Thanks @npathai , I have gone through the all the microsoft cloud design patterns, Some of the paterns like "Cache Aside pattern" , "Runtime Reconfiguration Pattern ", "External Configuration Store pattern" etc are really very usefull for all the applications apart from cloud.

I will create some sample interfaces and related impl classes for "External Configuration Store " pattern and share the details with you for further inputs from all.

[iluwatar]

@satishnaidu are you working on this pattern? I'm about to revert under construction label since there is no progress.

[iluwatar]

This issue is free for taking again.

[satishnaidu]

@iluwatar , Sorry for responding lately, I have these changes in my local...but before checking the code I just want to someone review it.
Because, It's not just plain java classes, It is using yaml file, jersey jars also to implement these pattern.
Please let me know how to proceed on this.

[iluwatar]

Are the changes in your fork? I can take a look if you point me in the right spot.

[iluwatar]

This issue is free for taking again.

[iluwatar]

https://docs.microsoft.com/en-us/azure/architecture/patterns/external-configuration-store

[iluwatar]

Updated task description