Initial example of generating Prometheus SDK metrics from Otel semconv with the weaver tool.

Makefile

@@ -20,14 +20,18 @@ $(BUF):
 MDOX = mdox
 $(MDOX):
 	@go install github.com/bwplotka/mdox@latest
+
+# Hacky, replace the binary path for yourself for now.
+# One could use docker as well. TODO: Fix this.
+WEAVER = ../otel-weaver/target/debug/weaver
+
 # ------
 
 .PHONY: help
 help: ## Display this help and any documented user-facing targets. Other undocumented targets may be present in the Makefile.
 help:
 	@awk 'BEGIN {FS = ": ##"; printf "Usage:\n  make <target>\n\nTargets:\n"} /^[a-zA-Z0-9_\.\-\/%]+: ##/ { printf "  %-45s %s\n", $$1, $$2 }' $(MAKEFILE_LIST)
 
-
 .PHONY: docker
 docker:
 	@export DOCKER_IMAGE=$(DOCKER_IMAGE) DOCKER_TAG=$(DOCKER_TAG) && bash scripts/build-docker.sh $(DOCKER_PUSH)
@@ -49,3 +53,13 @@ format: $(GOFUMPT) $(GOIMPORTS) $(MDOX)
 	@echo ">> format documentation"
 	@$(MDOX) fmt --soft-wraps ./*.md
 
+SEMCONV_VERSION ?= v0.1.0
+.PHONY: gen # Generate artefacts e.g. metric definitions from my-org semconv.
+gen:
+	@echo ">> weaver generate"
+	@$(WEAVER) registry generate \
+		--registry=./my-org/semconv/$(SEMCONV_VERSION) \
+		--templates=./client_golang/semconv \
+		go \
+		./go/my-app/semconv/$(SEMCONV_VERSION)
+

client_golang/semconv/registry/go/metric.go.j2

@@ -0,0 +1,87 @@
+{%- set my_file_name = ctx.metric_name | lower | snake_case ~ ".go" -%}
+{{- template.set_file_name(my_file_name) -}}
+{% set construct_name = ctx.id.split('.')[-1] %}
+{%- set instrToVecTypes = {
+ 	'counter': "CounterVec",
+  'gauge': "GaugeVec",
+}-%}
+{%- set instrToOptTypes = {
+ 	'counter': "CounterOpts",
+	'gauge': "GaugeOpts",
+}-%}
+{%- set labelTypeToTypes = {
+	'string': "string",
+ 	'int': "int",
+	'double': "float64",
+}-%}
+{% macro const_label_type(label) -%}
+{{ construct_name | pascal_case ~ label.tag | pascal_case }}
+{%- endmacro %}
+// Copyright 2025 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Code generated from semantic convention specification. DO NOT EDIT.
+
+package semconv // TODO(bwplotka): Use id prefix or something more unique?
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+{%- for label in ctx.attributes -%}
+	{%- if label.type.members is defined %}
+
+type {{ const_label_type(label) }} string
+
+const (
+	{%- for value in label.type.members %}
+		{{ value.id | pascal_case }}{{ const_label_type(label) }} {{ const_label_type(label) }} = "{{ value.value }}"
+	{%- endfor %}
+)
+	{%- endif %}
+{%- endfor %}
+
+func MustNew{{ construct_name | pascal_case }}{{ ctx.instrument | pascal_case }}Vec(reg prometheus.Registerer) *prometheus.{{ instrToVecTypes[ctx.instrument] }} {
+	return promauto.With(reg).New{{ instrToVecTypes[ctx.instrument] }}(prometheus.{{ instrToOptTypes[ctx.instrument] }}{
+		Name: "{{ ctx.metric_name }}",
+		{% if ctx.note is defined -%}
+		Help: "{{ ctx.note }}",
+		{% else -%}
+		Help: "{{ ctx.brief }}",
+		{%- endif %}
+		// Unit: "{{ ctx.unit }}" // TODO(bwplotka): Add Unit as one of the supported options.
+	}, []string{
+{%- for label in ctx.attributes %}
+		"{{label.tag}}",
+{%- endfor %}
+	})
+}
+
+/*
+TODO(bwplotka): Add more type safety e.g. for CustomElementsCounterVec:
+
+type CustomElementsCounterVec struct {
+	prometheus.CounterVec
+}
+
+func (v *CustomElementsCounterVec) WithLabelValues(integer int, category CustomElementsCategory, fraction float64) prometheus.Counter {
+	// This is not ideal as we do, potentially expensive stringifying on the hot path.
+  // Fix might require internals to completely differ in the client_golang for the efficient solution.
+	return v.CounterVec.WithLabelValues(fmt.Sprintf("%v", integer), string(category), fmt.Sprintf("%v", fraction))
+}
+*/
+
+
+
+

client_golang/semconv/registry/go/weaver.yaml

@@ -0,0 +1,17 @@
+templates:
+- template: metric.go.j2
+  filter: >
+    .groups
+    | map(select(.type == "metric"))
+    | sort_by(.metric_name)
+  application_mode: each
+
+comment_formats:
+  go:
+    format: markdown
+    prefix: "// "
+    indent_first_level_list_items: true
+    shortcut_reference_link: true
+    trim: true
+    remove_trailing_dots: true
+default_comment_format: go

go/my-app/main.go

@@ -3,11 +3,13 @@ package main
 import (
 	"context"
 	"flag"
+	"log"
 	"log/slog"
 	"net/http"
 	"os"
 	"syscall"
 
+	semconv "github.com/bwplotka/metric-rename-demo/go/my-app/my-app/semconv/v0.1.0"
 	"github.com/nelkinda/health-go"
 	"github.com/oklog/run"
 	"github.com/prometheus/client_golang/prometheus"
@@ -18,6 +20,7 @@ import (
 
 func main() {
 	addrFlag := flag.String("listen-address", ":9011", "Address to listen on. Available HTTP paths: /metrics")
+	metricDefinition := flag.String("metric-source", "manual", "Metric definition source to use ['manual', 'generated@v0.1.0'")
 	flag.Parse()
 
 	reg := prometheus.NewRegistry()
@@ -26,12 +29,16 @@ func main() {
 		collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}),
 	)
 
-	customStableMetric := promauto.With(reg).NewCounterVec(prometheus.CounterOpts{
-		Name: "my_app_custom_counter_total",
-		Help: "Custom counter metric for my app counts important things. It serves as an example " +
-				"of a very important metric that everyone is using.",
-	}, []string{"integer", "category", "fraction"})
-	customStableMetric.WithLabelValues("101", "AType", "1.22314").Inc()
+	switch *metricDefinition {
+	case "manual":
+		m := mustNewCustomStableMetric(reg)
+		m.WithLabelValues("101", "a", "1.22314").Inc()
+	case "generated@v0.1.0":
+		m := semconv.MustNewCustomElementsCounterVec(reg)
+		m.WithLabelValues("101", string(semconv.ACustomElementsCategory), "1.22314").Inc() // TODO(bwplotka): Make it more type safe.
+	default:
+		log.Fatalf("unknown -metric-source source, got %v", *metricDefinition)
+	}
 
 	var g run.Group
 	{

go/my-app/manual.go

@@ -0,0 +1,14 @@
+package main
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+func mustNewCustomStableMetric(reg prometheus.Registerer) *prometheus.CounterVec {
+	return promauto.With(reg).NewCounterVec(prometheus.CounterOpts{
+		Name: "my_app_custom_elements_total",
+		Help: "Custom counter metric for my app counting important elements. It serves as an example " +
+				"of a very important metric that everyone is using.",
+	}, []string{"integer", "category", "fraction"})
+}

my-org/semconv/v0.1.0/my-app.yaml

@@ -0,0 +1,45 @@
+# Schema: https://github.com/open-telemetry/weaver/blob/main/schemas/semconv.schema.json
+groups:
+- id: metric.my-org.custom_elements
+  type: metric
+  metric_name: my_app_custom_elements_total
+  brief: "Custom counter metric for my app counting important elements. It serves as an example of a very important metric that everyone is using."
+  instrument: counter
+  # Unit schema: https://github.com/open-telemetry/semantic-conventions/blob/main/docs/general/metrics.md#instrument-units
+  # It comes from https://unitsofmeasure.org/ucum standard.
+  unit: "{elements}"
+  attributes:
+  - id: metric.my-org.custom_elements.integer
+    tag: "integer"
+    type: int
+    brief: |
+      This is an important label that specifies the integer for this count.
+  - id: metric.my-org.custom_elements.category
+    tag: "category"
+    type:
+      members:
+      - id: a
+        value: "a"
+        stability: stable
+      - id: b
+        value: "b"
+        stability: stable
+      - id: other
+        value: "other"
+        stability: stable
+    brief: |
+      This is an important label that specifies the category for this count.
+  - id: metric.my-org.custom_elements.fraction
+    tag: "fraction"
+    type: double
+    brief: |
+      This is an important label that specifies the fraction for this count.
+  stability: stable
+- id: metric.my-org.some_elements
+  type: metric
+  metric_name: my_app_some_elements_total
+  deprecated: "Deprecated, not needed anymore"
+  brief: "old metric"
+  instrument: counter
+  unit: "{unknown}"
+  stability: experimental