Deploy

Production Deploy Mode

CRITICAL: This mode is for production servers serving multiple concurrent users. Widgets are stateless. State lives externally. Scale horizontally.

What Deploy Mode IS

You're creating widgets for a production SSE server with:

• Multiple concurrent users/sessions
• Stateless widget creation
• Horizontal scaling support
• Persistent widget URLs

Architecture

                         ┌─────────────────┐
                         │  Load Balancer  │
                         └────────┬────────┘
                                  │
         ┌────────────────────────┼────────────────────────┐
         │                        │                        │
         ▼                        ▼                        ▼
┌─────────────────┐      ┌─────────────────┐      ┌─────────────────┐
│  PyWry Server   │      │  PyWry Server   │      │  PyWry Server   │
│    (SSE #1)     │      │    (SSE #2)     │      │    (SSE #3)     │
└─────────────────┘      └─────────────────┘      └─────────────────┘
         │                        │                        │
         └────────────────────────┼────────────────────────┘
                                  │
                                  ▼
                      ┌───────────────────────┐
                      │   Shared State Store  │
                      │   (Redis / Database)  │
                      └───────────────────────┘

Key Principles

Widgets Are Stateless

• Widget instances don't persist server state
• Store state externally (Redis, database, etc.)
• Any server can handle any widget update

Session Management

• Each user gets a unique widget_id
• Map widget_id to user session externally
• Implement timeouts and cleanup

Horizontal Scaling

• Servers behind load balancer
• SSE connections are per-server (sticky sessions may help)
• Widget operations are idempotent

Best Practices

1. Widget IDs - Use Meaningful IDs

# Include user/session info in widget_id
widget_id = f"user_{user_id}_dashboard"

# Or use session-scoped IDs
widget_id = f"session_{session_id}_chart"

# This makes debugging and monitoring easier

2. State - Store Externally

# BAD: State in widget
widget_state = {"threshold": 0.5}  # Lost on server restart

# GOOD: State in external store
redis.set(f"widget:{widget_id}:state", json.dumps({"threshold": 0.5}))

# On event:
state = json.loads(redis.get(f"widget:{widget_id}:state"))

3. Cleanup - Destroy Widgets

# Implement session timeouts
def cleanup_expired_sessions():
    for widget_id in list_widgets():
        if is_expired(widget_id):
            destroy_widget(widget_id)
            redis.delete(f"widget:{widget_id}:*")

# Call on disconnect
events = get_events(widget_id, clear=True)
for e in events:
    if e["event_type"] == "pywry:disconnect":
        destroy_widget(widget_id)

4. Theme - User Choice

# Don't force dark/light - let users choose
# Store preference in user settings
user_prefs = get_user_preferences(user_id)
update_theme(widget_id, theme=user_prefs.get("theme", "system"))

Recommended Components

Multi-User Considerations

No Cross-Talk

# Events are per-widget
# User A's events don't appear in User B's widget
events_a = get_events(widget_id_a, clear=True)  # Only user A's events
events_b = get_events(widget_id_b, clear=True)  # Only user B's events

Session Monitoring

# Monitor active sessions
active_widgets = list_widgets()
print(f"Active sessions: {len(active_widgets)}")

# Check specific widget
if widget_id in active_widgets:
    # Widget still active
    pass

Broadcast Updates

# Send updates to multiple widgets
for widget_id in get_widgets_by_room("market-updates"):
    send_event(widget_id, event_type="price:update", data=new_prices)

Scaling Patterns

Sticky Sessions (Simple)

# nginx.conf
upstream pywry_servers {
    ip_hash;  # Same client → same server
    server pywry1:8001;
    server pywry2:8001;
    server pywry3:8001;
}

Redis Pub/Sub (Advanced)

# Publish updates to all servers
redis.publish("widget:updates", json.dumps({
    "widget_id": widget_id,
    "event_type": "data:refresh",
    "data": new_data
}))

# Servers subscribe and forward
def handle_redis_message(message):
    data = json.loads(message)
    send_event(data["widget_id"], data["event_type"], data["data"])

Code Example

import asyncio
import json
from pywry import PyWry
from pywry.toolbar import Div, Button, Toolbar
from redis import Redis

app = PyWry()
redis = Redis()

def create_user_dashboard(user_id: str, session_id: str):
    """Create a dashboard widget for a user session."""
    widget_id = f"user_{user_id}_{session_id}"

    # Load user state from Redis
    state = json.loads(redis.get(f"state:{widget_id}") or "{}")

    content = Div(
        content=f"""
            <div id="dashboard">
                <h1>Welcome, User {user_id}</h1>
                <div id="data-area">Loading...</div>
            </div>
        """,
        component_id="main",
    )

    widget = app.show(
        html=content.build_html(),
        height=600,
        toolbars=[
            Toolbar(
                position="top",
                items=[
                    Button(label="Refresh", event="refresh", variant="primary"),
                    Button(label="Export", event="export"),
                    Button(label="Logout", event="logout", variant="danger"),
                ]
            )
        ]
    )

    # Track session
    redis.setex(f"session:{widget_id}", 3600, user_id)  # 1 hour TTL

    return widget

async def handle_session(widget_id: str):
    """Handle events for a user session."""
    while True:
        events = get_events(widget_id, clear=True)

        for e in events:
            if e["event_type"] == "pywry:disconnect":
                # Cleanup
                destroy_widget(widget_id)
                redis.delete(f"session:{widget_id}")
                redis.delete(f"state:{widget_id}")
                return

            elif e["event_type"] == "refresh":
                data = fetch_user_data(widget_id)
                set_content(widget_id, component_id="data-area", html=render_data(data))

            elif e["event_type"] == "logout":
                destroy_widget(widget_id)
                return

        await asyncio.sleep(0.1)

Production Checklist

• Widget IDs include user/session info
• State stored in external store (Redis/DB)
• Session timeouts implemented
• destroy_widget called on disconnect
• Error handling for all operations
• Logging for debugging
• Metrics for monitoring (active sessions, events/sec)
• Load balancer configured
• Health check endpoint available