Event notifications

• Also referred to as "Event stream subscriptions"
• Asynchronous events
• Allow a plugin to subscribe to event topics such that CLN will send the plugin a push notification whenever events corresponding to such topics occur.
• For events where it doesn’t matter how many plugins are listening to the event or in what order the event is processed.
• Topics include:
  • channel_opened
  • connect
  • sendpay_success
  • block_added

For the full list of topics, see the official docs.

Exercise: Add an event stream subscription to your plugin

Add this code to your main.rs file (hint: insert this before .dynamic()):

.subscribe("connect", connect_handler)

This registers the plugin to listen for connect events and respond with a handler, named connect_handler.

Now add the connect_handler event notification handler function (this should go after your rpc handler, function, at the bottom of the file):

async fn connect_handler(_p: Plugin<()>, v: serde_json::Value) -> Result<(), Error> {
    log::info!("Got a connect notification: {}", v);
    Ok(())
}

Now let's test! Go to the shell and rebuild:

cargo build

Now restart your plugin:

l1-cli plugin stop rust-plugin && 
l1-cli plugin start $(pwd)/target/debug/rust-plugin

Grab Node 1’s pubkey and listening address:

l1-cli getinfo

Now paste the connection info for Node 1 into this connect command from Node 2:

l2-cli connect <Node 1’s pubkey>@<hostname>:<port>

Now check Node 1's logs to make sure your callback ran.

• Add an event stream subscription
• Test that it works as expected