fix(pubsub): enhance message validation and routing robustness

[pranavkonde]

Description

This PR improves the robustness and monitoring capabilities of PubSub message validation and routing. It addresses potential issues with message handling, adds rate limiting, and introduces comprehensive metrics for better observability.

Changes

Message Validation Improvements

• Added basic message validation checks (topic and data presence)
• Implemented message size limits (1MB max)
• Enhanced signature validation with better error reporting
• Added validation timing measurements
• Added detailed validation metrics

Message Routing Enhancements

• Implemented per-peer rate limiting (100 messages per minute)
• Added automatic cleanup of rate limiting state
• Improved error handling with detailed logging
• Added processing timing measurements

New Metrics

Added comprehensive metrics for monitoring:

• Message validation metrics
  • libp2p_pubsub_message_validation_total
  • libp2p_pubsub_message_validation_failed_signature
  • libp2p_pubsub_message_validation_failed_topic
  • libp2p_pubsub_message_validation_success
  • libp2p_pubsub_message_validation_time (histogram)
• Message processing metrics
  • libp2p_pubsub_message_processed_total
  • libp2p_pubsub_rate_limit_exceeded
  • libp2p_pubsub_message_dropped_invalid
  • libp2p_pubsub_message_delivered
  • libp2p_pubsub_message_processing_time (histogram)
  • libp2p_pubsub_message_processing_failed

[achingbrain]

Thank you for opening this PR.

Is this in response to an issue you’ve seen in a deployed application or are you just trying to make general improvements to the codebase?

[pranavkonde]

Thank you for opening this PR.

Is this in response to an issue you’ve seen in a deployed application or are you just trying to make general improvements to the codebase?

Thank you for the quick response!
This PR is based on general improvements to make the codebase more robust.