Specs

connection(status :: :up | :down) :: any()

Called when the MQTT connection changes status

This can be used to inform other parts of the system about the state of the connection; possible values are :up and :down, where up means that the MQTT client has a connection to the broker; down means that the connection has been dropped.

Specs

handle_error(reason) :: any()
when reason:
       {:publish_error, {topic(), payload(), opts}, error_reason :: term()}
       | {:publish_error, jackalope_work_order :: term(), :ttl_expired},
     opts: Keyword.t()

Handle errors produced by Jackalope that should be reacted to

During the connection life-cycle various errors can occur, and while Jackrabbit and Tortoise311 will try to correct the situation, some errors require user intervention. The optional handle_error/1 callback can help inform the surrounding system of errors.

@impl Jackalope.Handler
def handle_error({:publish_error, work_order, :ttl_expired}) do
  Logger.error("Work order expired: #{inspect(work_order)}")
end

def handle_error(_otherwise) do
  _ignore = nil
end

If this callback is implemented one should make sure to make a catch-all to prevent unhandled errors from crashing the handler.

Specs

handle_message(topic_levels(), payload()) :: any()

Called when receiving a message matching one of the subscriptions

The callback will receive two arguments; the MQTT topic in list form, where each of the topic levels are an item. This allows us to pattern match on topic filters with wildcards.

Specs

last_will() :: last_will() | nil

Produces the last will message for the current connection, or nil if the last will in the connection options is to be used Example: [topic: hub_serial_number/message", payload: %{code: "going_down", msg: "Last will message"}, qos: 1]

Specs

subscription(status :: :up | :down, topic_filter()) :: any()

Called when a topic filter subscription state changes

This can be used to inform other parts of the system that we should (or shouldn't) expect messages received on the given topic_filter.

The status values are :up and :down, where up means that the broker has accepted a subscription request to the specific topic_filter, and down means that the broker has accepted an unsubscribe request.