@ -15,7 +15,7 @@ They may be enabled by default in future versions.
`--enable-feature=exemplar-storage`
`--enable-feature=exemplar-storage`
[OpenMetrics](https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#exemplars) introduces the ability for scrape targets to add exemplars to certain metrics. Exemplars are references to data outside of the MetricSet. A common use case are IDs of program traces.
[OpenMetrics](https://github.com/prometheus/OpenMetrics/blob/v1.0.0/specification/OpenMetrics.md#exemplars) introduces the ability for scrape targets to add exemplars to certain metrics. Exemplars are references to data outside of the MetricSet. A common use case are IDs of program traces.
Exemplar storage is implemented as a fixed size circular buffer that stores exemplars in memory for all series. Enabling this feature will enable the storage of exemplars scraped by Prometheus. The config file block [storage](configuration/configuration.md#configuration-file)/[exemplars](configuration/configuration.md#exemplars) can be used to control the size of circular buffer by # of exemplars. An exemplar with just a `trace_id=<jaeger-trace-id>` uses roughly 100 bytes of memory via the in-memory exemplar storage. If the exemplar storage is enabled, we will also append the exemplars to WAL for local persistence (for WAL duration).
Exemplar storage is implemented as a fixed size circular buffer that stores exemplars in memory for all series. Enabling this feature will enable the storage of exemplars scraped by Prometheus. The config file block [storage](configuration/configuration.md#configuration-file)/[exemplars](configuration/configuration.md#exemplars) can be used to control the size of circular buffer by # of exemplars. An exemplar with just a `trace_id=<jaeger-trace-id>` uses roughly 100 bytes of memory via the in-memory exemplar storage. If the exemplar storage is enabled, we will also append the exemplars to WAL for local persistence (for WAL duration).
// Conversion taken from common/expfmt.writeOpenMetricsFloat.
// Conversion taken from common/expfmt.writeOpenMetricsFloat.
// We don't check the ct timestamp as explicit ts was not implemented in expfmt.Encoder,
// We don't check the ct timestamp as explicit ts was not implemented in expfmt.Encoder,
// but exists in OM https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#:~:text=An%20example%20with%20a%20Metric%20with%20no%20labels%2C%20and%20a%20MetricPoint%20with%20a%20timestamp%20and%20a%20created
// but exists in OM https://github.com/prometheus/OpenMetrics/blob/v1.0.0/specification/OpenMetrics.md#:~:text=An%20example%20with%20a%20Metric%20with%20no%20labels%2C%20and%20a%20MetricPoint%20with%20a%20timestamp%20and%20a%20created
// We can implement this, but we want to potentially get rid of OM 1.0 CT lines
// We can implement this, but we want to potentially get rid of OM 1.0 CT lines
// OTLP metrics use the c/s notation as specified at https://ucum.org/ucum.html
// OTLP metrics use the c/s notation as specified at https://ucum.org/ucum.html
// (See also https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/semantic_conventions/README.md#instrument-units)
// (See also https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/semantic_conventions/README.md#instrument-units)
// Prometheus best practices for units: https://prometheus.io/docs/practices/naming/#base-units
// Prometheus best practices for units: https://prometheus.io/docs/practices/naming/#base-units
// OpenMetrics specification for units: https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#units-and-base-units
// OpenMetrics specification for units: https://github.com/prometheus/OpenMetrics/blob/v1.0.0/specification/OpenMetrics.md#units-and-base-units