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ZeroMQ Trigger

Starts a workflow when a ZeroMQ message is received

ZeroMQ Trigger

AI-generated

Overview

This node acts as a trigger that starts an n8n workflow when a message is received on a ZeroMQ socket. It supports three types of ZeroMQ sockets: Reply (REP), Subscribe (SUB), and Pull. The node can either bind to a socket address (acting as a server) or connect to an existing server socket.

Common scenarios include:

  • Listening for messages published on a specific topic in a pub-sub pattern (SUB).
  • Receiving requests and sending automatic replies in a request-reply pattern (REP).
  • Pulling messages from a pipeline of tasks or workers (PULL).

Practical examples:

  • Subscribing to sensor data updates published on a certain topic.
  • Acting as a service that receives commands and sends acknowledgments automatically.
  • Pulling jobs from a distributed queue for processing.

Properties

Name Meaning
Socket Type Type of ZeroMQ socket to use. Options: Reply (REP), Subscribe (SUB), Pull
Action Whether to bind (act as server and listen) or connect (connect to a server)
Socket Address The ZeroMQ socket address, e.g., tcp://127.0.0.1:5555
Topic (Only for SUB) The topic to subscribe to. Leave empty to receive all topics
Response (for REP) (Only for REP) Automatic response message sent upon receiving a message

Output

The node outputs JSON objects with the following structure:

  • For SUB sockets:

    {
  "topic": "<topic string>",
  "message": "<message string>"
}

    Where topic is the subscribed topic and message is the content of the message received.

  • For REP sockets:

    {
  "message": "<message string>"
}

    The message received from the requester. The node also sends back an automatic response configured by the user.

  • For PULL sockets:

    {
  "message": "<message string>"
}

    The pulled message from the connected socket.

No binary data output is produced by this node.

Dependencies

  • Requires the zeromq Node.js package to interact with ZeroMQ sockets.
  • Needs a running ZeroMQ server or publisher to connect or bind to.
  • No special environment variables are required beyond standard network connectivity.

Troubleshooting

  • Invalid socket type error: Occurs if an unsupported socket type is selected. Ensure the socket type is one of REP, SUB, or PULL.
  • Connection errors: If binding or connecting to the specified socket address fails, verify the address format and that the target server is reachable.
  • No messages received: For SUB sockets, ensure the topic matches what publishers send; leaving it empty subscribes to all topics.
  • Unexpected behavior with REP sockets: The node automatically sends a fixed response after receiving a message. Customize the response property as needed.
  • Resource cleanup: The node closes the socket properly on workflow stop, but if errors occur, check network stability and socket lifecycle.

Links and References

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