How to fix "This aggregator does not support recording long values" when using a gauge with callback?

[gabrielgiussi]

I'm getting the following error but I don't know where should I configure a different kind of aggregator.

WARNING: An exception occurred invoking callback for Instrument some-instrument.
java.lang.UnsupportedOperationException: This aggregator does not support recording long values.
	at io.opentelemetry.sdk.metrics.internal.aggregator.AggregatorHandle.doRecordLong(AggregatorHandle.java:126)
	at io.opentelemetry.sdk.metrics.internal.aggregator.AggregatorHandle.recordLong(AggregatorHandle.java:117)
	at io.opentelemetry.sdk.metrics.internal.aggregator.AggregatorHandle.recordLong(AggregatorHandle.java:106)
	at io.opentelemetry.sdk.metrics.internal.aggregator.Aggregator.accumulateLongMeasurement(Aggregator.java:60)
	at io.opentelemetry.sdk.metrics.internal.state.AsynchronousMetricStorage.recordLong(AsynchronousMetricStorage.java:94)
	at io.opentelemetry.sdk.metrics.internal.state.SdkObservableMeasurement.record(SdkObservableMeasurement.java:96)
	at io.opentelemetry.sdk.metrics.internal.state.SdkObservableMeasurement.record(SdkObservableMeasurement.java:80)

I've added the following dependencies to a clojure deps project.

io.opentelemetry/opentelemetry-api {:mvn/version "1.19.0"}
io.opentelemetry/opentelemetry-sdk {:mvn/version "1.19.0"}
io.opentelemetry/opentelemetry-exporter-otlp {:mvn/version "1.19.0"}
io.opentelemetry/opentelemetry-exporter-logging {:mvn/version "1.19.0"}
io.grpc/grpc-stub {:mvn/version "1.49.1"}

And the code to trigger this exception is the following

(ns otel
  (:require [clojure.string :as str])
  (:import (io.opentelemetry.api GlobalOpenTelemetry)
           (io.opentelemetry.api.metrics Meter ObservableDoubleMeasurement)
           (io.opentelemetry.sdk.metrics SdkMeterProvider)
           (io.opentelemetry.sdk.metrics.export PeriodicMetricReader MetricExporter)
           (io.opentelemetry.exporter.otlp.metrics OtlpGrpcMetricExporter)
           (io.opentelemetry.sdk OpenTelemetrySdk)
           (io.opentelemetry.sdk.common CompletableResultCode)
           (io.opentelemetry.sdk.metrics.data AggregationTemporality)
           (io.opentelemetry.exporter.logging LoggingMetricExporter)))

(defn getCpuUsage [] 42)

(let [sdk-provider (-> (SdkMeterProvider/builder)
                       (.registerMetricReader (.build (PeriodicMetricReader/builder (LoggingMetricExporter/create))))
                       (.build))]
  (-> (OpenTelemetrySdk/builder)
      (.setMeterProvider sdk-provider)
      (.buildAndRegisterGlobal)))

(def ^Meter meter (-> (GlobalOpenTelemetry/get)
                      (.meterBuilder "poc")
                      (.setInstrumentationVersion "1.0.0")
                      (.build)))

(-> (.gaugeBuilder meter "some-instrument")
    (.buildWithCallback (reify java.util.function.Consumer
                          (accept [_ measurement]
                            (println "observing measurement")
                            (.record measurement (getCpuUsage))))))

[gabrielgiussi]

It was just a matter of returning a double in getCpuUsage instead of a long 🤦 , I can't delete this discussion though.

[jkwatson]

It might help someone in the future, so glad you figured it out. Also, great to see some clojure!