In process metrics

[pescuma]

Is it possible to store the metrics in memory and use them inside the process itself? I'd like to use this to show some metrics while running some processor heavy tasks in a cli (and at the same time send those to Prometheus if the user wants).

[tobz]

Recording metrics in-memory

It's possible to use something like DebuggingRecorder to achieve that. You would create the recorder, use DebuggingRecorder::snapshotter to get a Snapshotter, which is a handle to take a snapshot of metrics, and then install the recorder.

One thing to note is that DebuggingRecorder takes a lock when describing and registering new metrics, so if you're using the macros in a dynamic way -- such as increment_counter!("my_metric", &some_var_with_dynamic_labels) -- you'd be "registering" the counter every time that call was made, which would go through the locking path.

This lock is also accessed to take a snapshot of the recorder, so the insert performance, as well as the potential contention when taking snapshots, may be noticeable at high metrics emission rates if you're emitting many "dynamic" metrics.

Also sending metrics to Prometheus

You could utilize layers to achieve this, specifically the Fanout layer, which lets you fanout metrics to one or more recorders.

You would create the DebuggingRecorder and PrometheusRecorder recorders and add them both to FanoutBuilder. You'd then build the Fanout layer, which could be via metrics::set_boxed_recorder(Box::new(your_fanout)).

[pescuma]

Thanks, I'll try.