DDP ClientInstall

Overview

This node establishes a connection to a DDP (Distributed Data Protocol) server via WebSocket. It allows subscribing to specific data streams ("subscriptions") and monitoring collections for real-time changes. When data in the subscribed collections changes, the node emits updated JSON data.

Common scenarios include integrating with Meteor.js backends or other services using DDP for real-time data synchronization. For example, it can be used to listen to live updates of user data, chat messages, or any reactive data source exposed by a DDP server.

Properties

Output

The node outputs JSON arrays where each item corresponds to a monitored collection. Each output item has the structure:

{
  "name": "collectionName",
  "data": [ /* array of documents from the collection */ ]
}

This output reflects the current state of the collection whenever it changes.

The node does not output binary data.

Dependencies

• Requires access to a DDP server supporting WebSocket connections.
• Uses the simpleddp library for DDP protocol handling.
• Uses the ws library as the WebSocket client implementation.
• No internal n8n credentials are required, but the URL must point to a valid DDP WebSocket endpoint.

Troubleshooting

• Connection timeout error: If the node cannot establish a connection within 5 minutes, it throws a timeout error. Ensure the URL is correct and the DDP server is reachable.
• Connection lost error: If the WebSocket connection drops unexpectedly, an error is emitted. Check network stability and server availability.
• Subscription issues: If subscriptions do not receive data, verify that the subscription names are correct and that the server supports them.
• Collection monitoring: If no data is emitted for collections, ensure the collection names exist on the server and that the server sends reactive updates.

Links and References

• DDP Protocol Specification
• simpleddp GitHub Repository
• WebSocket API Documentation