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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. As minutely probes are instances of EventEmitters, they are asynchronous.

No minutely probes are configured by @appsignal/nodejs by default.

Creating probes

If you need to track custom metrics from your app, you can add your own probe(s). Using a probe will be familiar to you if you have used an EventEmitter before; the probes.register() method takes two arguments: a probe name and an anonymous function to be called once every minute.

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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);
});

As with most, if not all, usages of an EventEmitter, it is crucial not to block the event loop for long periods inside a minutely probe callback.

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