config: add reusable exporter config package

config/config.go

@@ -0,0 +1,54 @@
+// Copyright 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 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")
+	}
+}