echo-otel-metrics

this is an opentelemetry metrics middleware for echo http framework.

it addd a custom opentelemetry metrics middleware otelmetric to echo framework, and setup a prometheus exporter endpoint at /metrics.

this otelmetric middleware can work as a replacement for

https://github.com/labstack/echo-contrib/tree/master/echoprometheus

or the legacy https://github.com/labstack/echo-contrib/tree/master/prometheus

as of this module get v0.3.0 (otel metric v1.16.0), the metrics component is stable now, so this middleware is stable too.

but the metrics name diffs.

counter

requests_total

histogram

ref https://opentelemetry.io/docs/specs/semconv/http/http-metrics/

request_duration_seconds{_bucket, _sum, _count}

request_size_bytes{_bucket, _sum, _count}

response_size_bytes{_bucket, _sum, _count}

echo's middleware result:

request_duration_seconds_bucket{code="200",host="example.com",method="GET",url="/",le="0.005"}

but this one result:

request_duration_milliseconds_bucket{code="200",method="GET",otel_scope_name="echo",otel_scope_version="",url="/",le="5"}

and otel metric exporter also add an target_info gauge looks like:

target_info{service_name="otelmetric-demo",telemetry_sdk_language="go",telemetry_sdk_name="opentelemetry",telemetry_sdk_version="1.16.0"} 1

---

The echoprometheus middleware registers the following metrics by default:

• Counter requests_total
• Histogram request_duration_seconds
• Histogram response_size_bytes
• Histogram request_size_bytes

histogram will have _bucket, _sum, _count suffix.

warning

status https://opentelemetry.io/docs/instrumentation/go/

the Metrics component for OpenTelemetry Go is Stable now!

see https://github.com/open-telemetry/opentelemetry-go/releases/tag/v1.16.0

prometheus related

Unit 1

https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/compatibility/prometheus_and_openmetrics.md#metric-metadata-1

The Unit of an OTLP metric point SHOULD be converted to the equivalent unit in Prometheus when possible. This includes:

• Special case: Converting "1" to "ratio".

open-telemetry/opentelemetry-collector-contrib#10554 Metrics about offset should use an empty unit. Unit 1 must be used only for fractions and ratios.

https://github.com/open-telemetry/opentelemetry-specification/blob/ce360a26894271fa9a2b0c846a78d97d277e4183/specification/metrics/semantic_conventions/README.md#instrument-units

Instrument Units

Units should follow the Unified Code for Units of Measure.

• Instruments for utilization metrics (that measure the fraction out of a total) are dimensionless and SHOULD use the default unit 1 (the unity).
• All non-units that use curly braces to annotate a quantity need to match the grammatical number of the quantity it represent. For example if measuring the number of individual requests to a process the unit would be {request}, not {requests}.
• Instruments that measure an integer count of something SHOULD only use annotations with curly braces to give additional meaning without the leading default unit (1). For example, use {packet}, {error}, {fault}, etc.
• Instrument units other than 1 and those that use annotations SHOULD be specified using the UCUM case sensitive ("c/s") variant. For example, "Cel" for the unit with full name "degree Celsius".
• Instruments SHOULD use non-prefixed units (i.e. By instead of MiBy) unless there is good technical reason to not do so.
• When instruments are measuring durations, seconds (i.e. s) SHOULD be used.

https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/8f394d4ffea8d5f06a9019245746ff253be106fd/pkg/translator/prometheus/normalize_name.go#L155-L162

Metric name normalization

https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/8f394d4ffea8d5f06a9019245746ff253be106fd/pkg/translator/prometheus/README.md#full-normalization

https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/pkg/translator/prometheus/README.md#full-normalization

docs

the implementation ref to https://github.com/labstack/echo-contrib/blob/master/prometheus/prometheus.go

https://uptrace.dev/opentelemetry/go-metrics.html

https://uptrace.dev/opentelemetry/prometheus-metrics.html#sending-go-metrics-to-prometheus

https://opentelemetry.io/docs/reference/specification/metrics/sdk/

https://echo.labstack.com/cookbook/hello-world/

semconv

https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/semantic_conventions/README.md#document-conventions https://github.com/open-telemetry/opentelemetry-go/blob/main/semconv/v1.12.0/resource.go

http server

https://opentelemetry.io/docs/specs/semconv/attributes-registry/server/

https://opentelemetry.io/docs/specs/semconv/http/http-metrics/