Add per-database _config API endpointAdd per db config api 5685

[harshitydv1]

This PR implements a new /{db}/_config API endpoint that provides a unified, extensible interface for database-specific configuration settings, as requested in issue #5685.

Overview

The implementation follows the pattern of the server-level /_config API and consolidates existing per-database configuration endpoints (_revs_limit, _purged_infos_limit, _auto_purge) into a cohesive structure while maintaining full backward compatibility.

Changes Made

Modified Files

1. src/chttpd/src/chttpd_httpd_handlers.erl (1 line added)

   • Registered handler for _config endpoint

2. src/chttpd/src/chttpd_db.erl (~220 lines added)

   • Added export for handle_db_config_req/2
   • Implemented main handler function with routing for GET, PUT, DELETE operations
   • Added comprehensive helper functions for configuration management

API Endpoints

GET /{db}/_config

Returns all configuration sections and their values.

Example Response:

{
  "revs": {"limit": 1000},
  "purges": {"limit": 1000},
  "auto_purge": {"deleted_document_ttl": null},
  "compaction": {"generations": 0}
}

GET /{db}/_config/{section}

Returns all keys in a specific section.

Example: GET /mydb/_config/revs

{"limit": 1000}

GET /{db}/_config/{section}/{key}

Returns a specific configuration value.

Example: GET /mydb/_config/revs/limit → 1000

PUT /{db}/_config/{section}/{key}

Updates a configuration value and returns the old value.

Example: PUT /mydb/_config/revs/limit with body 2000 → returns 1000

DELETE /{db}/_config/{section}/{key}

Resets a configuration value to its default and returns the old value.

Supported Configuration Sections

1. revs Section

• Key: limit (integer, default: 1000)
• Description: Maximum number of document revisions to track
• Replaces: /{db}/_revs_limit (still supported for backward compatibility)

2. purges Section

• Key: limit (positive integer, default: 1000)
• Description: Maximum number of purge requests to store
• Replaces: /{db}/_purged_infos_limit (still supported for backward compatibility)

3. auto_purge Section

• Key: deleted_document_ttl (string, default: null)
• Description: Time-to-live for deleted documents before auto-purge (e.g., "30d", "7d")
• Replaces: /{db}/_auto_purge (still supported for backward compatibility)

4. compaction Section

• Key: generations (integer, default: 0)
• Description: Generational compaction setting (reserved for future use)
• Status: Not yet implemented (returns error on PUT/DELETE)

Backward Compatibility

✅ All existing endpoints continue to work:

• /{db}/_revs_limit
• /{db}/_purged_infos_limit
• /{db}/_auto_purge

The new _config API internally uses the same fabric layer functions, ensuring consistency.

Implementation Details

• Follows existing CouchDB patterns and conventions
• Comprehensive input validation for all config keys
• Proper HTTP status codes and error messages
• Extensible design for adding new configuration options

Fixes #5685<!-- Thank you for your contribution!

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Overview

Testing recommendations

Related Issues or Pull Requests

Checklist

• Code is written and works correctly
• Changes are covered by tests
• Any new configurable parameters are documented in rel/overlay/etc/default.ini
• Documentation changes were made in the src/docs folder
• Documentation changes were backported (separated PR) to affected branches