fix: Handle empty datapoints in otel exporter

[jaydeluca]

From @dhoard on slack, There was an error in the jmx-exporter project smoke tests:

time=2026-02-16T15:49:03.466Z level=ERROR source=write_handler.go:652 msg="Error appending remote write" component=web err="empty data points. jvm_memory_pool_allocated_bytes is dropped"
2026-02-16 15:49:03.482 | OkHttp http://prometheus:9090/... | WARNING | e1723a08afd7bca35570fd31a7656f59.io.prometheus.metrics.shaded.io_opentelemetry_2_25_0_alpha.exporter.internal.http.HttpExporter | Failed to export metrics. Server responded with HTTP status code 500. Error message: Unable to parse response body, HTTP status message: Internal Server Error

Looking at the documentation for jvm_memory_pool_allocated_bytes... "Only updated after GC, not continuously." Most likely GC hasn't happened, yet the OTel exporter is trying to write the data.

I updated the method to return null when the data points are empty, which is then handled via the addUnlessNull method.

After applying this change locally, I ran the quick test a few times and the error was no longer present.

[Copilot]

Pull request overview

This PR fixes an issue where the OpenTelemetry exporter was attempting to export metrics with empty data points, causing server errors. The fix addresses a scenario where metrics like jvm_memory_pool_allocated_bytes are registered with label names but have no data points until after garbage collection occurs.

Changes:

• Added empty data point checks to all MetricDataFactory.create() methods to return null when no data points exist
• Made the test extension field static to properly share the OpenTelemetryExtension across tests
• Added comprehensive test case to verify metrics without data points are not exported

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
MetricDataFactory.java	Added @Nullable annotations and empty data point checks to all create methods (Counter, Gauge, Summary, Info, StateSet, Unknown)
ExportTest.java	Made OpenTelemetryExtension static and added test for metrics without data points

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[zeitlinger]

great!