lifecycle-events.md

Lifecycle Events

Glee lets you bind incoming messages to functions. However, sometimes we need to be proactive and be the first ones to send a message, not necessarily as a reaction to another message. Use cases can be very diverse: from sending a message to announce our client is connected to sending a message every few seconds or minutes.

To subscribe to a lifecycle event, create a file under the lifecycle directory. It must have the following shape:

export default async function ({
  glee,
  serverName,
  server,
  connection,
}) {
  // Your business logic here...
}

export const lifecycleEvent = 'onConnect'

Each file in the lifecycle directory must export a default async function and the lifecycleEvent field, which is the name of the event you want to subscribe to. Optionally, your function can return an object following exactly the same syntax as described in the functions documentation.

List of events

Event	Description
onConnect	A connection with a broker has been established.
onReconnect	Glee reconnected to a broker.
onDisconnect	A connection with a broker has been closed.
onServerReady	Your Glee server is now ready to accept connections.
onServerConnectionOpen	A client has opened a connection with your Glee server.
onServerConnectionClose	A client has closed the connection with your Glee server.

All of them take a single argument which contains information about the event:

Attribute	Description
glee	A reference to the Glee app.
serverName	The name of the server where the event happened.
server	The AsyncAPI definition of the server where the event happened.
connection	The connection where the event happened.

Restricting the lifecycle event

In some cases it's useful to restrict the lifecycle event to a specific server or set of servers. To do that, add a line like the following to your lifecycle file:

export const servers = ['mosquitto']

The above example makes Glee fire the lifecycle event only if it's coming from the mosquitto server.

Additionally, you may want to restrict the lifecycle event by channel/topic. To do that, add a line like the following to your lifecycle file:

export const servers = ['user/signedup']

The above example makes Glee fire the lifecycle event only if the connection has the channel user/signedup listed as one of its channels.