collector: add reusable runtime wrapper

collector/runtime.go

@@ -0,0 +1,69 @@
+// Copyright 2026 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.
+
+package collector
+
+import (
+	"log/slog"
+	"sort"
+
+	"github.com/prometheus/client_golang/prometheus"
+
+	"github.com/prometheus/node_exporter/config"
+)
+
+// Runtime represents a single exporter runtime instance built from a reusable
+// Config.
+type Runtime struct {
+	collector *NodeCollector
+}
+
+func NewRuntime(cfg config.Config, logger *slog.Logger) (*Runtime, error) {
+	if err := cfg.Validate(); err != nil {
+		return nil, err
+	}
+
+	if cfg.CollectorDisableDefaults {
+		DisableDefaultCollectors()
+	}
+
+	nodeCollector, err := NewNodeCollector(logger, cfg.EnabledCollectors...)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Runtime{collector: nodeCollector}, nil
+}
+
+func (r *Runtime) Collectors() []prometheus.Collector {
+	return []prometheus.Collector{r.collector}
+}
+
+func (r *Runtime) Registry() (*prometheus.Registry, error) {
+	registry := prometheus.NewRegistry()
+	for _, c := range r.Collectors() {
+		if err := registry.Register(c); err != nil {
+			return nil, err
+		}
+	}
+	return registry, nil
+}
+
+func (r *Runtime) EnabledCollectors() []string {
+	enabled := make([]string, 0, len(r.collector.Collectors))
+	for name := range r.collector.Collectors {
+		enabled = append(enabled, name)
+	}
+	sort.Strings(enabled)
+	return enabled
+}

collector/runtime_test.go

@@ -0,0 +1,66 @@
+// Copyright 2026 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.
+
+package collector
+
+import (
+	"io"
+	"log/slog"
+	"testing"
+
+	"github.com/prometheus/node_exporter/config"
+)
+
+func TestNewRuntimeCollectors(t *testing.T) {
+	runtime, err := NewRuntime(config.NewConfigWithDefaults(), slog.New(slog.NewTextHandler(io.Discard, nil)))
+	if err != nil {
+		t.Fatalf("expected nil error, got %v", err)
+	}
+
+	if got, want := len(runtime.Collectors()), 1; got != want {
+		t.Errorf("Expected: %d, Got: %d", want, got)
+	}
+
+	if got := len(runtime.EnabledCollectors()); got == 0 {
+		t.Fatal("expected at least one enabled collector")
+	}
+}
+
+func TestNewRuntimeValidateConfig(t *testing.T) {
+	cfg := config.NewConfigWithDefaults()
+	cfg.RuntimeGoMaxProcs = 0
+
+	if _, err := NewRuntime(cfg, slog.New(slog.NewTextHandler(io.Discard, nil))); err == nil {
+		t.Fatal("expected error, got nil")
+	}
+}
+
+func TestRuntimeRegistry(t *testing.T) {
+	runtime, err := NewRuntime(config.NewConfigWithDefaults(), slog.New(slog.NewTextHandler(io.Discard, nil)))
+	if err != nil {
+		t.Fatalf("expected nil error, got %v", err)
+	}
+
+	registry, err := runtime.Registry()
+	if err != nil {
+		t.Fatalf("expected nil error, got %v", err)
+	}
+
+	metrics, err := registry.Gather()
+	if err != nil {
+		t.Fatalf("expected nil error, got %v", err)
+	}
+	if got := len(metrics); got == 0 {
+		t.Fatal("expected gathered metrics, got none")
+	}
+}

config/config.go

@@ -0,0 +1,54 @@
+// Copyright 2026 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.
+
+package config
+
+import "fmt"
+
+const (
+	DefaultWebTelemetryPath  = "/metrics"
+	DefaultWebMaxRequests    = 40
+	DefaultRuntimeGoMaxProcs = 1
+)
+
+// Config contains the user-facing configuration currently adapted by the
+// node_exporter binary into the reusable runtime and HTTP handler layers.
+type Config struct {
+	WebTelemetryPath          string
+	WebDisableExporterMetrics bool
+	WebMaxRequests            int
+	CollectorDisableDefaults  bool
+	RuntimeGoMaxProcs         int
+	EnabledCollectors         []string
+}
+
+func NewConfigWithDefaults() Config {
+	return Config{
+		WebTelemetryPath:  DefaultWebTelemetryPath,
+		WebMaxRequests:    DefaultWebMaxRequests,
+		RuntimeGoMaxProcs: DefaultRuntimeGoMaxProcs,
+	}
+}
+
+func (c Config) Validate() error {
+	if c.WebTelemetryPath == "" {
+		return fmt.Errorf("web telemetry path must not be empty")
+	}
+	if c.WebMaxRequests < 0 {
+		return fmt.Errorf("web max requests must be greater than or equal to zero")
+	}
+	if c.RuntimeGoMaxProcs <= 0 {
+		return fmt.Errorf("runtime gomaxprocs must be greater than zero")
+	}
+	return nil
+}

config/config_test.go

@@ -0,0 +1,65 @@
+// Copyright 2026 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.
+
+package config
+
+import "testing"
+
+func TestNewConfigWithDefaults(t *testing.T) {
+	cfg := NewConfigWithDefaults()
+
+	if got, want := cfg.WebTelemetryPath, DefaultWebTelemetryPath; got != want {
+		t.Errorf("Expected: %q, Got: %q", want, got)
+	}
+	if got, want := cfg.WebMaxRequests, DefaultWebMaxRequests; got != want {
+		t.Errorf("Expected: %d, Got: %d", want, got)
+	}
+	if got, want := cfg.RuntimeGoMaxProcs, DefaultRuntimeGoMaxProcs; got != want {
+		t.Errorf("Expected: %d, Got: %d", want, got)
+	}
+}
+
+func TestConfigValidate(t *testing.T) {
+	cfg := NewConfigWithDefaults()
+
+	if err := cfg.Validate(); err != nil {
+		t.Fatalf("expected nil error, got %v", err)
+	}
+}
+
+func TestConfigValidateRequiresTelemetryPath(t *testing.T) {
+	cfg := NewConfigWithDefaults()
+	cfg.WebTelemetryPath = ""
+
+	if err := cfg.Validate(); err == nil {
+		t.Fatal("expected error, got nil")
+	}
+}
+
+func TestConfigValidateRejectsNegativeMaxRequests(t *testing.T) {
+	cfg := NewConfigWithDefaults()
+	cfg.WebMaxRequests = -1
+
+	if err := cfg.Validate(); err == nil {
+		t.Fatal("expected error, got nil")
+	}
+}
+
+func TestConfigValidateRejectsNonPositiveGoMaxProcs(t *testing.T) {
+	cfg := NewConfigWithDefaults()
+	cfg.RuntimeGoMaxProcs = 0
+
+	if err := cfg.Validate(); err == nil {
+		t.Fatal("expected error, got nil")
+	}
+}