Limit metrics point amount

[xiangtianyu]

I used -Dotel.experimental.metrics.cardinality.limit to limit metrics cardinality, but i found histogram is different with other metrics type, if i set limit 5, histogram may upload about 5 * 15 = 75 records, is there some solution to set limit to the histogram and not effect the other metrics type

[trask]

You could use a metric view to override the buckets boundaries, in order to have less buckets

[jack-berg]

Yeah from the cardinality limit is indeed applied consistently to histograms as other instruments. The cardinality limits the total number of distinct metric points for a particular instrument. However, as you point out, histograms are different from other aggregations in that they contain more fields used to describe the distribution of measurement values, including: sum, count, min, max, and 0-N buckets where each bucket represents the count of measurements recorded with its boundaries. Bucket boundaries are the main thing that people configure with histograms, and there are a variety of tools for doing so:

• As @trask points out, you can use a view
• If you control the instrumentation, you can provide advice to influence the default bucket boundaries used by the SDK
• You can override your metric reader's default aggregation selector to change the default aggregation (including bucket boundaries) for all histogram instruments

[xiangtianyu]

Actually, i do not want to change the buckets boundaries, what i need is a dedicated configuration to limit the histogram count and not effect the other metrics types

[jack-berg]

What's the use case for limiting the the histogram count? Unless I'm misunderstanding, i don't think there's a way to achieve that.

[xiangtianyu]

Since histogram will generate much more records, it will cause more pressure on the server.
When we set -Dotel.experimental.metrics.cardinality.limit, if we set limit for histogram, it's too restrictive on other type; if we set limit for other, there will be huge data, and will cause high load,

[trask]

I think you will be able to set a different cardinality limit for histograms using a metric view starting from the next release

check out

• https://github.com/open-telemetry/opentelemetry-java/tree/main/sdk-extensions/incubator#view-file-configuration
• Stabilize metric cardinality limits APIs #6794