PubNub MCP Server

# How to Manage Concurrent Connections with PubNub PubNub is designed to support a massive number of concurrent connections, making it suitable for applications with large user bases. ## PubNub's Capacity * **Millions of Connections:** PubNub can support millions of concurrent connections (devices/users). Many customers have millions of users connecting and exchanging messages, leading to billions or even trillions of transactions. * **No Hard Limits (Generally):** PubNub does not impose hard limits on the number of concurrent users connected to the platform overall. * For PubNub Chat, while there's no limit on total concurrent users, it's recommended to limit online users in a *single chat room or space* to around 10,000 for optimal performance. For larger groups, consider sharding users into multiple spaces. * **Horizontal Scalability:** PubNub's infrastructure is built to scale horizontally, automatically handling spikes in traffic and ensuring consistent performance even during surges. ## When to Contact PubNub * If your application anticipates having **more than 1000 concurrent connections (devices/users) regularly**, it's recommended to contact PubNub. * **Benefits:** * Discuss a Pro plan for potential volume discounts. * Request a best practice architecture review with a PubNub expert to optimize your application for scale. * **Contact:** [PubNub Support](mailto:support@pubnub.com) or your dedicated account manager. ## Technical Aspects of Connections * **Connection Definition:** A "connection" in PubNub refers to an active client (e.g., a mobile app, browser, or IoT device) that is subscribed to one or more channels. * **Efficient Protocols:** PubNub utilizes efficient protocols like WebSockets and HTTP/2, enabling lightweight, persistent connections that reduce overhead and optimize bandwidth. This is crucial for supporting high concurrency. * **Long-Lived Keep-Alive Connections:** PubNub SDKs typically establish long-lived connections (e.g., one hour keep-alive, with pings every 5 minutes) to maintain connectivity efficiently, which is particularly important for mobile battery life. * **TCP Sockets:** Each PubNub client instance generally creates a small number of TCP socket connections (e.g., often two: one for subscribes and another for non-subscribe operations like publish, history, etc.). * **Global Edge Network:** PubNub's 15+ globally distributed data centers (Points of Presence - PoPs) ensure that users connect to the nearest server, minimizing latency and distributing connection load. ## Browser Connection Limits and Custom Origins * **Browser Limits:** Browsers impose their own limits on the number of concurrent connections a single tab can make to a specific hostname (e.g., Chrome typically allows 6 connections per hostname). * **Custom Origin:** If your application makes many types of requests to PubNub from the same client (beyond just a single subscribe loop), or if you have multiple PubNub instances in one page, you might approach these browser limits. A custom origin (e.g., `yoursubdomain.pubnubapi.com`) can help by allowing PubNub to route traffic per customer more effectively. While not a direct solution for browser per-hostname limits, it's part of a robust scaling strategy. * Refer to "Custom origin - what is it and how to use it" in `pubnub_troubleshooting.md` for more details on requesting one. ## Best Practices for High Concurrency * **Efficient Channel Subscriptions:** * Use **Multiplexing** to subscribe to multiple channels (up to ~30) over a single connection. * For larger numbers of channels, use **Channel Groups** (up to 2,000 channels per group, 10 groups per client). * Employ **Wildcard Subscriptions** for hierarchical channel structures. * **Optimize Message Payloads:** Keep messages small to reduce bandwidth and processing load per connection. * **Connection Management in SDKs:** Rely on the PubNub SDKs to manage connection establishment, keep-alives, and reconnections. Implement listeners for connection status events to handle them gracefully in your application. * **Presence Management:** For applications needing to know who is online, use PubNub's Presence feature efficiently. Be mindful of the number of presence events generated in very large channels. * **Authentication and Authorization:** Secure your connections and channels using PubNub Access Manager, especially at scale.