Improve Grafana query cache flexibility

[rishabhkailey]

Proposed changes

• Introduce query labels:
  • Enable attaching key-value pairs (labels) to queries using a comment in the query's first line (e.g., # dashboard=daily-metrics; data-source=timescaledb;).
  • Use labels to target specific queries for individualized caching behavior.
• Adopt YAML configuration:
  • Replace global environment variables with a YAML configuration file for advanced settings.
  • Specify default caching behavior for all queries.
  • Define customized caching configurations for queries matching specified labels.

Key benefits:

• Granular control: Tailor caching settings to specific query requirements, optimizing performance and resource usage.
• Improved flexibility : Easily adjust caching behavior without code changes, promoting adaptability to diverse scenarios.
• Enhanced maintainability: YAML configuration simplifies management and understanding of caching rules.

Requirements:

• Support first-line comments for query labels: Implement parsing logic to extract labels from comments.
• Implement YAML configuration parsing: Read and apply caching settings from the YAML configuration file.
• Apply query labels for caching: Use labels to match queries with their corresponding configurations.

Example YAML configuration:

# Default configuration for queries without label match:
default:
  enabled: true
  acceptableTimeDeltaSeconds: 600
  acceptableTimeRangeDeltaSeconds: 60
  acceptableMaxDataPointsDelta: 200

# Query-specific configuration using labels:
queryConfigs:
- querySelector:
    dashboard: daily-metrics
    data-source: timescaledb
  cacheConfig:
    enabled: true
    acceptableTimeDeltaSeconds: 2400
    acceptableTimeRangeDeltaSeconds: 600
    acceptableMaxDataPointsDelta: 300

Example query with label comment:

-- dashboard=daily-metrics; data-source=timescaledb;
SELECT ...