Pulsar Functions can publish arbitrary metrics to the metrics interface which can then be queried. This doc contains instructions for publishing metrics using the Java and Python Pulsar Functions SDKs.

Metrics and stats not available through language-native interfaces

If a Pulsar Function uses the language-native interface for Java or Python, that function will not be able to publish metrics and stats to Pulsar.

Accessing metrics

For a guide to accessing metrics created by Pulsar Functions, see the guide to Monitoring in Pulsar.

Java SDK

If you’re creating a Pulsar Function using the Java SDK, the Context object has a recordMetric method that you can use to register both a name for the metric and a value. Here’s the signature for that method:

void recordMetric(String metricName, double value);

Here’s an example function:

import org.apache.pulsar.functions.api.Context;
import org.apache.pulsar.functions.api.Function;
public class MetricRecordingFunction implements Function<String, Void> {
    @Override
    public void apply(String input, Context context) {
        context.recordMetric("number-of-characters", input.length());
        return null;
    }
}

This function counts the length of each incoming message (of type String) and then registers that under the number-of-characters metric.

Python SDK

Documentation for the Python SDK is coming soon.