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Prometheus Normalization

OpenTelemetry's metric semantic convention is not compatible with Prometheus' own metrics naming convention. This module provides centralized functions to convert OpenTelemetry metrics to Prometheus-compliant metrics. These functions are used by the following components for Prometheus:

Metric name

Full normalization

Warning

This feature can be enabled with feature gate pkg.translator.prometheus.NormalizeName. It is disabled by default (alpha stage).

$ otelcol --config=config.yaml --feature-gates=pkg.translator.prometheus.NormalizeName

List of transformations to convert OpenTelemetry metrics to Prometheus metrics

Case Transformation Example
Unsupported characters and extraneous underscores Replace unsupported characters with underscores (_). Drop redundant, leading and trailing underscores. (lambda).function.executions(#) → lambda_function_executions
Standard unit Convert the unit from Unified Code for Units of Measure to Prometheus standard and append system.filesystem.usage with unit By → system_filesystem_usage_bytes
Non-standard unit (unit is surrounded with {}) Drop the unit system.network.dropped with unit {packets} → system_network_dropped
Non-standard unit (unit is not surrounded with {}) Append the unit, if not already present, after sanitization (all non-alphanumeric chars are dropped) system.network.dropped with unit packets → system_network_dropped_packets
Percentages (unit is 1) Append _ratio (for gauges only) system.memory.utilization with unit 1 → system_memory_utilization_ratio
Percentages (unit is %) Replace % with percent _percent storage.filesystem.utilization with unit % → storage_filesystem_utilization_percent
Rates (unit contains /) Replace / with per astro.light.speed with unit m/s → astro_light_speed_meters_per_second
Dollars (unit is $) Replace $ with dollars crypto.dogecoin.value with unit $ → crypto_dogecoin_value_dollars
Counter Append _total system.processes.created → system_processes_created_total

List of standard OpenTelemetry units that will be translated to Prometheus standard base units:

OpenTelemetry Unit Corresponding Prometheus Unit
Time
d days
h hours
min minutes
s seconds
ms milliseconds
us microseconds
ns nanoseconds
Bytes
By bytes
KiBy kibibytes
MiBy mebibytes
GiBy gibibytes
TiBy tibibytes
KBy kilobytes
MBy megabytes
GBy gigabytes
TBy terabytes
B bytes
KB kilobytes
MB megabytes
GB gigabytes
TB terabytes
SI Units
m meters
V volts
A amperes
J joules
W watts
g grams
Misc.
Cel celsius
Hz hertz
% percent
$ dollars

Note Prometheus also recommends using base units (no kilobytes, or milliseconds, for example) but these functions will not attempt to convert non-base units to base units.

List of transformations performed to convert Prometheus metrics to OpenTelemetry metrics

Case Transformation Example
UNIT defined in OpenMetrics format Drop the unit suffix and set it in the OpenTelemetry metric unit field system_network_dropped_packets → system_network_dropped with packets unit
Counter Drop _total suffix system_processes_created_total→ system_processes_created

Simple normalization

If feature pkg.translator.prometheus.NormalizeName is not enabled, a simple sanitization of the OpenTelemetry metric name is performed to ensure it follows Prometheus naming conventions:

  • Drop unsupported characters and replace with underscores (_)
  • Remove redundant, leading and trailing underscores
  • Ensure metric name doesn't start with a digit by prefixing with an underscore

No processing of the unit is performed, and _total is not appended for Counters.

Labels

OpenTelemetry Attributes are converted to Prometheus labels and normalized to follow the Prometheus labels naming rules.

The following transformations are performed on OpenTelemetry Attributes to produce Prometheus labels:

  • Drop unsupported characters and replace with underscores (_)
  • Prefix label with key_ if it doesn't start with a letter, except if it's already prefixed with double-underscore (__)

By default, labels that start with a simple underscore (_) are prefixed with key, which is strictly unnecessary to follow Prometheus labels naming rules. This behavior can be disabled with the feature pkg.translator.prometheus.PermissiveLabelSanitization, which must be activated with the feature gate option of the collector:

$ otelcol --config=config.yaml --feature-gates=pkg.translator.prometheus.PermissiveLabelSanitization

Examples:

OpenTelemetry Attribute Prometheus Label
name name
host.name host_name
host_name host_name
name (of the host) name__of_the_host_
2 cents key_2_cents
__name __name
_name key_name
_name _name (if PermissiveLabelSanitization is enabled)