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5e871e81a8
* otel to 1.24 * prometheus exporter to 0.46 * bunotel to 1.1.17 Also: * Use schemaless URL for metrics * Add software version to tracing schema
113 lines
3.7 KiB
Markdown
113 lines
3.7 KiB
Markdown
# Experimental Features
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The metric SDK contains features that have not yet stabilized in the OpenTelemetry specification.
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These features are added to the OpenTelemetry Go metric SDK prior to stabilization in the specification so that users can start experimenting with them and provide feedback.
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These feature may change in backwards incompatible ways as feedback is applied.
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See the [Compatibility and Stability](#compatibility-and-stability) section for more information.
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## Features
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- [Cardinality Limit](#cardinality-limit)
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- [Exemplars](#exemplars)
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### Cardinality Limit
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The cardinality limit is the hard limit on the number of metric streams that can be collected for a single instrument.
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This experimental feature can be enabled by setting the `OTEL_GO_X_CARDINALITY_LIMIT` environment value.
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The value must be an integer value.
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All other values are ignored.
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If the value set is less than or equal to `0`, no limit will be applied.
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#### Examples
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Set the cardinality limit to 2000.
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```console
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export OTEL_GO_X_CARDINALITY_LIMIT=2000
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```
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Set an infinite cardinality limit (functionally equivalent to disabling the feature).
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```console
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export OTEL_GO_X_CARDINALITY_LIMIT=-1
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```
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Disable the cardinality limit.
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```console
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unset OTEL_GO_X_CARDINALITY_LIMIT
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```
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### Exemplars
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A sample of measurements made may be exported directly as a set of exemplars.
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This experimental feature can be enabled by setting the `OTEL_GO_X_EXEMPLAR` environment variable.
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The value of must be the case-insensitive string of `"true"` to enable the feature.
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All other values are ignored.
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Exemplar filters are a supported.
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The exemplar filter applies to all measurements made.
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They filter these measurements, only allowing certain measurements to be passed to the underlying exemplar reservoir.
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To change the exemplar filter from the default `"trace_based"` filter set the `OTEL_METRICS_EXEMPLAR_FILTER` environment variable.
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The value must be the case-sensitive string defined by the [OpenTelemetry specification].
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- `"always_on"`: allows all measurements
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- `"always_off"`: denies all measurements
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- `"trace_based"`: allows only sampled measurements
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All values other than these will result in the default, `"trace_based"`, exemplar filter being used.
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[OpenTelemetry specification]: https://github.com/open-telemetry/opentelemetry-specification/blob/a6ca2fd484c9e76fe1d8e1c79c99f08f4745b5ee/specification/configuration/sdk-environment-variables.md#exemplar
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#### Examples
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Enable exemplars to be exported.
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```console
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export OTEL_GO_X_EXEMPLAR=true
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```
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Disable exemplars from being exported.
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```console
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unset OTEL_GO_X_EXEMPLAR
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```
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Set the exemplar filter to allow all measurements.
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```console
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export OTEL_METRICS_EXEMPLAR_FILTER=always_on
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```
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Set the exemplar filter to deny all measurements.
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```console
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export OTEL_METRICS_EXEMPLAR_FILTER=always_off
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```
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Set the exemplar filter to only allow sampled measurements.
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```console
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export OTEL_METRICS_EXEMPLAR_FILTER=trace_based
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```
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Revert to the default exemplar filter (`"trace_based"`)
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```console
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unset OTEL_METRICS_EXEMPLAR_FILTER
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```
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## Compatibility and Stability
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Experimental features do not fall within the scope of the OpenTelemetry Go versioning and stability [policy](../../../../VERSIONING.md).
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These features may be removed or modified in successive version releases, including patch versions.
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When an experimental feature is promoted to a stable feature, a migration path will be included in the changelog entry of the release.
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There is no guarantee that any environment variable feature flags that enabled the experimental feature will be supported by the stable version.
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If they are supported, they may be accompanied with a deprecation notice stating a timeline for the removal of that support.
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