Session Management

This document explains how Omnia manages conversation sessions for AI agents.

What is a Session?

A session represents a single conversation between a client and an agent. It maintains:

• Conversation history - All messages exchanged
• Agent state - Internal state maintained by the agent
• Metadata - Custom data attached to the session

Sessions enable multi-turn conversations where the agent remembers previous context.

Session Lifecycle

Creation

A new session is created when:

1. A client connects without providing a session ID
2. A client provides a session ID that doesn’t exist or has expired

The server assigns a unique session ID and returns it in the connected message.

Active

While active, a session:

• Stores new messages as they’re exchanged
• Maintains the agent’s internal state
• Tracks the last activity timestamp

Expiration

Sessions expire after a period of inactivity defined by session.ttl. When expired:

• The session data is deleted
• Attempting to resume creates a new session
• The conversation history is lost

Session Stores

In-Memory Store

The simplest option, suitable for development:

session:
  type: memory
  ttl: 1h

Characteristics:

• Fast access
• No external dependencies
• Lost on pod restart
• Not suitable for multiple replicas

Redis Store

Production-ready distributed storage:

session:
  type: redis
  ttl: 24h
  storeRef:
    name: redis-credentials
    key: url

Characteristics:

• Persistent across restarts
• Works with multiple replicas
• Supports large session counts
• Requires Redis infrastructure

Session Resumption

Clients can resume sessions by including the session ID:

{
  "type": "message",
  "session_id": "sess-abc123",
  "content": "What did we discuss earlier?"
}

Resumption Flow

1. Client sends message with session ID
2. Server looks up session in store
3. If found and not expired:
   • Load conversation history
   • Process new message with context
4. If not found:
   • Create new session
   • Process message without history

Cross-Replica Resumption

With Redis sessions, clients can resume on any replica:

Client ──▶ Load Balancer ──▶ Any Agent Pod ──▶ Redis

Session Data Structure

Each session stores:

type Session struct {
    ID        string
    AgentName string
    Messages  []Message
    State     map[string]interface{}
    Metadata  map[string]interface{}
    CreatedAt time.Time
    UpdatedAt time.Time
}

Messages

The conversation history:

type Message struct {
    Role      string  // "user", "assistant", "tool"
    Content   string
    Timestamp time.Time
}

State

Agent-specific state that persists across messages. Useful for:

• Tracking conversation progress
• Storing extracted entities
• Managing multi-step workflows

Metadata

Client-provided metadata:

{
  "type": "message",
  "content": "...",
  "metadata": {
    "user_id": "user-123",
    "source": "mobile-app"
  }
}

TTL Considerations

Choosing a TTL

TTL and Memory

Longer TTLs require more storage:

• Each message adds to session size
• Tool calls include full arguments/results
• Consider message pruning for long sessions

TTL Refresh

TTL is refreshed on every activity:

1. Client sends message
2. Server updates UpdatedAt timestamp
3. TTL countdown restarts

Scaling Considerations

Single Replica

With one replica, in-memory sessions work fine. But:

• Sessions are lost on pod restart
• No horizontal scaling

Multiple Replicas

With multiple replicas, you must use Redis:

1. Install Redis in your cluster
2. Configure session.type: redis
3. All replicas share session state

Session Affinity Alternative

If you can’t use Redis, configure service affinity:

apiVersion: v1
kind: Service
spec:
  sessionAffinity: ClientIP

This routes the same client to the same pod, but:

• Sessions still lost on pod restart
• Uneven load distribution
• Not recommended for production

Best Practices

1. Use Redis for production - Always use Redis with multiple replicas
2. Set appropriate TTLs - Balance memory usage with user experience
3. Handle expiration gracefully - Clients should expect session loss
4. Don’t store sensitive data - Sessions may be logged or cached
5. Monitor session counts - Alert on unusual growth