LLMChat Multi-Worker: Add Documentation and Integration Tests (PR #1236 Follow-up)

[crivetimihai]

Summary

PR #1236 adds Redis-based session consistency for LLMChat multi-worker deployments. While the implementation is well-architected and solves a real problem, there are several follow-up tasks to ensure production readiness.

PR #1236 Overview

• Changes: 786 additions / 295 deletions
• Key Components:
  • New ChatHistoryManager class for centralized history management
  • Redis-based distributed session storage with fallback to in-memory
  • Worker coordination with distributed locking
  • TTL-based session ownership (SESSION_TTL=300s, LOCK_TTL=30s)
• Status: All 36 CI checks passing

Required Documentation Updates

1. Redis Setup Requirements

Add documentation covering:

• Redis installation and configuration for multi-worker deployments
• Environment variables for Redis connection (REDIS_URL, CACHE_TYPE)
• Session management environment variables:
  • LLMCHAT_SESSION_TTL (default: 300 seconds)
  • LLMCHAT_LOCK_TTL (default: 30 seconds)
  • LLMCHAT_LOCK_TIMEOUT (default: 10 seconds)
  • LLMCHAT_MAX_HISTORY_MESSAGES (default: 50)

2. Architecture Documentation

Document the new multi-worker architecture:

• How worker coordination works
• Session ownership and TTL behavior
• Distributed locking mechanism
• Automatic session recreation from stored config
• Fallback behavior when Redis is unavailable

Recommended Integration Tests

1. Multi-Worker Coordination Tests

• Session handoff between workers
• Distributed lock acquisition and release
• Race condition scenarios with concurrent requests
• Session TTL expiration and renewal
• Lock timeout handling

2. Redis Failure Scenarios

• Graceful degradation when Redis is unavailable
• Fallback to in-memory storage
• Redis connection loss during active session
• Redis recovery and session restoration

3. Chat History Persistence Tests

• History preservation across worker restarts
• Message ordering with concurrent appends
• History size limits and trimming behavior
• Clear history operations across workers

Monitoring Recommendations

Add observability for:

• Session recreation frequency (potential indicator of TTL tuning needs)
• Lock contention metrics
• Redis connection health
• Worker session distribution

Configuration Improvements

Consider moving hardcoded tunables to config.py:

# Currently in llmchat_router.py:
SESSION_TTL = int(os.getenv("LLMCHAT_SESSION_TTL", "300"))
LOCK_TTL = int(os.getenv("LLMCHAT_LOCK_TTL", "30"))
LOCK_TIMEOUT = int(os.getenv("LLMCHAT_LOCK_TIMEOUT", "10"))
MAX_HISTORY_MESSAGES = int(os.getenv("LLMCHAT_MAX_HISTORY_MESSAGES", "50"))

# Should be in config.py with proper Pydantic validation:
llmchat_session_ttl: PositiveInt = Field(default=300)
llmchat_lock_ttl: PositiveInt = Field(default=30)
llmchat_lock_timeout: PositiveInt = Field(default=10)
llmchat_max_history_messages: PositiveInt = Field(default=50)

Related Files

• mcpgateway/services/mcp_client_chat_service.py - ChatHistoryManager class (lines 1193-1454)
• mcpgateway/routers/llmchat_router.py - Worker coordination logic (lines 407-669)
• mcpgateway/config.py - Potential location for configuration additions

References

• PR LLMChat add session consistency using redis #1236: LLMChat add session consistency using redis #1236