Minutely probes

Minutely probes are a mechanism to periodically send custom metrics to AppSignal. In minutely intervals from when the probe was first created, a user-defined function can be called in which you can capture metrics to send them to AppSignal. Minutely probe functions are ran asynchronously.

Starting with version 2.3.0, you can enable or disable minutely probes entirely with the enableMinutelyProbes config option.

Creating probes

If you need to track custom metrics from your app, you can add your own probe(s). To register a probe, you must call the probes.register() method with two arguments: a probe name, and an anonymous function to be called once every minute.

const meter = appsignal.metrics();
const probes = meter.probes();
 
// the callback is fired once every minute from when
// `register` is called
probes.register("database", () => {
  meter.setGauge("database_size", 10);
});

To ensure all minutely probes are ran in a timely manner, it is important to avoid blocking the event loop for long periods inside a minutely probe callback.

Overriding default probes

By default, @appsignal/nodejs configures a minutely probe which keeps track of Node.js V8 heap statistics. To disable this probe, use probes.unregister():

const probes = appsignal.metrics().probes();
 
probes.unregister("v8_stats");

Before version 2.3.0, probes.unregister() is not available. In versions before 2.3.0, you can use the enableMinutelyProbes config option to disable the default probe.