NGINX Plus 37 introduces a new metric, but it is currently missing from the agent.

Bug Overview

NGINX Plus 37 introduces a new upstream latency metric, response_time_hist, but this metric is currently not collected or exported by the agent.
According to the NGINX Plus 37 release notes, this release adds enhanced upstream latency metrics using latency histograms:

Enhanced upstream latency metrics with latency histograms: the response_time_hist data for each HTTP upstream.

This metrics provides a more detailed view of upstream performance, making it easier to understand latency distributions, analyze percentiles, identify outliers, and correlate upstream behavior with other NGINX Plus metrics and insights.

Currently, the agent collector and nginxplus receiver do not include support for this new metric. Without support for response_time_hist, users will not have visibility into the new upstream latency histogram data, which limits their ability to monitor upstream performance and troubleshoot latency issues.

Expected Behavior

The agent should collect the response_time_hist metric from the NGINX Plus API and export it through the existing metrics pipeline.

Steps to Reproduce the Bug

The collector and nginxplus receiver do not currently include the new response_time_hist metric.

Environment Details

• Target deployment platform: Any platform using NGINX Plus 37 that relies on nginx-agent to collect and emit the said metric.

Additional Context

No response

Start by locating the agent collector and nginxplus receiver that read metrics from the NGINX Plus API. Trace how existing upstream metrics move through the metrics pipeline, then add coverage for response_time_hist using the NGINX Plus 37 API and verify that the histogram data is collected and exported.