github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheus

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:

• prometheusreceiver
• prometheusexporter
• prometheusremotewriteexporter

Metric name

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
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
SI Units
m	meters
V	volts
A	amperes
J	joules
W	watts
g	grams
Misc.
Cel	celsius
Hz	hertz
%	percent

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

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 (__). This is to provide compatibility with OpenMetrics 1.0.

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)