NNG Pub/Sub Bridging

NanoMQ supports data bridging with NNG (Next Generation Scalability Protocols) pub0/sub0 protocols, leveraging its underlying NanoNNG engine. This is particularly useful in edge computing scenarios where you need to interface standard MQTT with high-throughput NNG-based internal message buses.

NNG bridging is divided into two directions: NNG Pub Bridge (forwarding MQTT messages to NNG) and NNG Sub Bridge (receiving NNG messages and publishing them as MQTT).

NNG Pub Bridge (bridges.nng.pub)

The NNG Pub Bridge is responsible for forwarding MQTT messages from local topics to a remote NNG pub0 socket.

• Data Flow: MQTT PUBLISH → NNG pub0 message.
• Workflow: MQTT Client publishes to local_topic → Bridge subscribes and extracts the payload → Payload is prefixed with remote_topic + nng_delimiter (default /) → Sent to NNG pub socket.

Configuration Example

bridges.nng.pub.t1 {
    # Enable or disable this bridge.
    #
    # Value: true | false
    # Default: false
    enable = true

    # NNG pub socket URL.
    # The address of the NNG pub0 protocol server to publish to.
    #
    # Value: String
    # Example: tcp://127.0.0.1:9900
    #          ipc:///tmp/nng_pub.ipc
    #          inproc://nng_pub_inproc (Use for Inter-process communication)
    pub_url = "tcp://localhost:9900"

    # The ClientId of this NNG bridge publisher.
    # Default random string.
    #
    # Value: String
    clientid = "nng_proxy"

    # Topics that need to be forwarded to NNG.
    # This defines mappings between local MQTT topics and remote NNG topics.
    #
    # Value: Array of objects
    forwards = [
        {
            # Local MQTT topic filter to subscribe to.
            # Messages matching this filter are forwarded.
            # Supports MQTT wildcards (# and +).
            #
            # Value: String
            local_topic = "nng/#"

            # Remote NNG topic to publish to.
            # NNG message format:
            # "remote_topic + nng_delimiter + payload"
            # If remote_topic is empty, it is treated as local_topic.
            #
            # Value: String
            remote_topic = "remote/nng"

            # Delimiter between remote_topic and payload in NNG message.
            # Default delimiter is "/".
            # Example with ":" -> "remote_topic:payload".
            #
            # Value: String
            nng_delimiter = ":"

            # QoS level for MQTT messages from local_topic.
            # Value: 0 | 1 | 2
            qos = 1
        },
        {
            local_topic = "ekuiper/"
            # Example of fallback behavior:
            # when remote_topic is empty, remote_topic = local_topic.
            remote_topic = ""
            nng_delimiter = "/"
        }
    ]
}

Parameters

• bridges.nng.pub.<name>: Defines an NNG Pub bridge instance, where <name> is a unique identifier (e.g., t1).
• enable: Whether to enable this bridge. Value: true | false. Default: false.
• pub_url: The address on which NanoMQ listens with its NNG pub0 socket. External NNG sub clients connect to this address to receive messages. Supports various transports such as tcp://127.0.0.1:9900, ipc:///tmp/nng_pub.ipc or inproc://inproc_thr.
• clientid: Identifier for this bridge publisher within the local NanoMQ broker.
• forwards: Array of mapping rules between local MQTT topics and remote NNG topics.
  • local_topic: The local MQTT topic filter to subscribe to. Supports wildcards (# and +).
  • remote_topic: The topic prefix prepended to the payload when sending to the NNG side. The constructed NNG message format is: "remote_topic + nng_delimiter + payload". If remote_topic is omitted or set to an empty string, it is treated as local_topic.
  • nng_delimiter: Delimiter inserted between remote_topic and payload when building NNG messages. Default: /. Example: : produces remote_topic:payload.
  • qos: QoS level used for the internal subscription to local_topic. Value: 0 | 1 | 2.

---

NNG Sub Bridge (bridges.nng.sub)

The NNG Sub Bridge subscribes to topics on a remote NNG sub0 socket and forwards received messages as MQTT publications to a local topic.

• Data Flow: NNG sub0 message → MQTT PUBLISH.
• Workflow: NNG pub socket sends message with prefix → Bridge matches remote_topic + nng_delimiter (default /) → Forwards remainder of message as MQTT payload to local_topic.

Configuration Example

bridges.nng.sub.t2 {
    # Enable or disable this bridge.
    #
    # Value: true | false
    # Default: false
    enable = true

    # NNG sub socket URL.
    # The address of the NNG sub0 protocol server to subscribe to.
    #
    # Value: String
    # Example: tcp://127.0.0.1:9901
    #          ipc:///tmp/nng_sub.ipc
    #          inproc://nng_sub_inproc (Use for Inter-process communication)
    sub_url = "tcp://localhost:9901"

    # The ClientId of this NNG bridge subscriber.
    # Default random string.
    #
    # Value: String
    clientid = "nng_proxy_2"

    # Subscription topics from remote NNG server.
    # This defines mappings between remote NNG topics and local MQTT topics.
    #
    # Value: Array of objects
    subscription = [
        {
            # Remote NNG topic to subscribe to.
            # Topic extraction rules:
            # 1) If nng_delimiter is not set or is "/":
            #    extracted topic is matched against configured remote_topic,
            #    and the matched suffix (the part after matched prefix)
            #    becomes payload.
            #    Example: remote_topic="nng/pub", nng_delimiter="/",
            #    msg="nng/pub/123/hello" -> extracted topic="nng/pub",
            #    payload="123/hello".
            # 2) If nng_delimiter is set to non-"/" (e.g. ":"):
            #    extracted topic extends from remote_topic prefix to delimiter,
            #    and the part after delimiter becomes payload.
            #    Example: remote_topic="nng/pub", nng_delimiter=":",
            #    msg="nng/pub/123/1234:payload" ->
            #    extracted topic="nng/pub/123/1234", payload="payload".
            #
            # Value: String
            remote_topic = "nng"

            # Delimiter between remote_topic and payload in incoming NNG message.
            # Default delimiter is "/".
            #
            # Value: String
            nng_delimiter = "/"

            # Local MQTT topic to publish to.
            # If local_topic is empty, local_topic is treated as remote_topic.
            #
            # Value: String
            local_topic = "local/nng"

            # QoS level for MQTT messages published to local_topic.
            # Value: 0 | 1 | 2
            qos = 1
        },
        {
            remote_topic = "ekuiper"
            nng_delimiter = ":"
            local_topic = "local/ekuiper"
        }
    ]
}

Parameters

• bridges.nng.sub.<name>: Defines an NNG Sub bridge instance, where <name> is a unique identifier (e.g., t2).
• enable: Whether to enable this bridge. Value: true | false. Default: false.
• sub_url: The address on which NanoMQ listens with its NNG sub0 socket. External NNG pub clients connect to this address to push messages. Supports TCP and IPC transports, e.g., tcp://localhost:9901, ipc:///tmp/nng_sub.ipc or inproc://inproc_thr.
• clientid: Identifier for this bridge subscriber within the local NanoMQ broker.
• subscription: Array of mapping rules between remote NNG topics and local MQTT topics.
  • remote_topic: The NNG topic prefix to subscribe to. Topic extraction rules:
    • If nng_delimiter is not set or is /: extracted topic is matched against configured remote_topic, and the matched suffix (the part after matched prefix) becomes payload. Example: remote_topic="nng/pub", nng_delimiter="/", message "nng/pub/123/hello" → extracted topic="nng/pub", payload="123/hello".
    • If nng_delimiter is set to non-/ (e.g. ":"): extracted topic extends from remote_topic prefix to delimiter, and the part after delimiter becomes payload. Example: remote_topic="nng/pub", nng_delimiter=":", message "nng/pub/123/1234:payload" → extracted topic="nng/pub/123/1234", payload="payload".
  • nng_delimiter: Delimiter used when matching remote_topic and splitting payload from incoming NNG messages. Default: /.
  • local_topic: The local MQTT topic to which the forwarded message will be published. If local_topic is omitted or set to an empty string, it is treated as remote_topic.
  • qos: QoS level used when publishing the message to the local broker. Value: 0 | 1 | 2.