NanoMQ Broker

The system configuration provides settings to control the number of task queue threads, the maximum number of concurrent tasks, and cache settings in NanoMQ broker.

Task Queue

Example Configuration

system {
    num_taskq_thread = 0  # Use a specified number of task queue threads
    max_taskq_thread = 0  # Use a specified maximum number of task queue threads
    parallel = 0          # Handle a specified maximum number of outstanding requests
}

Configuration Item

• num_taskq_thread: Specifies the number of task queue threads to use.
  • Acceptable range: uint32, Recommend 1 - Core * 2. If the value is set to 0, the system automatically determines the number of threads.
• max_taskq_thread: Specifies the maximum number of task queue threads to use.
  • Acceptable range: uint32, Recommend 1 - Core * 2. If the value is set to 0, the system automatically determines the maximum number of threads.
• parallel: Specifies the maximum number of outstanding requests that the system can handle at once.
  • Acceptable range: uint32, Recommend Core * 4. No upper limit, however, too much parallel context actually hurt performance. If the value is set to 0, the system automatically determines the number of parallel tasks.

Cache

NanoMQ uses SQLite to cache MQTT data bridge.

Example Configuration

sqlite {
    disk_cache_size = 102400  # Max number of messages for caching
    mounted_file_path="/tmp/" # Mounted file path 
    flush_mem_threshold = 100 # The threshold number of flushing messages to flash
    resend_interval = 5000    # Resend interval (ms)
}

Configuration Items

• disk_cache_size: Specifies the maximum number of messages that can be cached in the SQLite database.
  • Value range: 1 - infinity. If the value is set to 0, then cache for messages is ineffecitve.
  • default: 102400.
• mounted_file_path: Specifies the file path where SQLite database file is mounted.
  • default: nanomq running path
• flush_mem_threshold: Specifies the threshold for flushing messages to the SQLite database. When the number of messages reaches the threshold, they will be flushed to the SQLite database.
  • Value range: 1 - infinity
  • default: 100.
• resend_interval: (Currently not implemented) Specifies the interval, in milliseconds, for resending the messages after a failure is recovered. This is unrelated to the trigger for the resend operation. Note: Only work for the NanoMQ broker to resend cached messages to local client, not for bridging connections.
  • default: 5000.

Preset Sessions

With preset sessions, You can publish messages to a void client, that is not connected yet. QoS messages will be cached just like session keeping However, the new coming client still need to subscribe to the target topics by itself.

Example Configuration

preset.session.1 {
	clientid = "example"
	topic = [
		{
			qos = 2
			remote_topic = "msg1/#"
		},
		{
			qos = 1
			remote_topic = "msg2/#"
		}
	]
}
preset.session.2 {
    ......
}

Each section is a preset session of a non-connected client, specifying the subscribed topics, QoS, and client ID. Once the (real) client is connected, the preset session will be taken over, all the following works are governed by MQTT persist session then.

Configuration Items

• clientid：the client ID of preset session.
  • must to have, UTF-8 String.
• remote_topic：Subscribed topic of preset session client.
  • As same as normal topics, QoS messages went into these topics will be cached.
• qos：Corresponding QOS of subscription
  • must be 1 or 2.