global: split Akvorado into 3 services

cmd/config.go

@@ -0,0 +1,107 @@
+package cmd
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/mitchellh/mapstructure"
+	"gopkg.in/yaml.v2"
+
+	"akvorado/inlet/flow"
+)
+
+// ConfigRelatedOptions are command-line options related to handling a
+// configuration file.
+type ConfigRelatedOptions struct {
+	Path string
+	Dump bool
+}
+
+// Parse parses the configuration file (if present) and the
+// environment variables into the provided configuration.
+func (c ConfigRelatedOptions) Parse(out io.Writer, component string, config interface{}) error {
+	var rawConfig map[string]interface{}
+	if cfgFile := c.Path; cfgFile != "" {
+		input, err := ioutil.ReadFile(cfgFile)
+		if err != nil {
+			return fmt.Errorf("unable to read configuration file: %w", err)
+		}
+		if err := yaml.Unmarshal(input, &rawConfig); err != nil {
+			return fmt.Errorf("unable to parse configuration file: %w", err)
+		}
+	}
+
+	// Parse provided configuration
+	decoder, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{
+		Result:           &config,
+		ErrorUnused:      true,
+		Metadata:         nil,
+		WeaklyTypedInput: true,
+		MatchName: func(mapKey, fieldName string) bool {
+			key := strings.ToLower(strings.ReplaceAll(mapKey, "-", ""))
+			field := strings.ToLower(fieldName)
+			return key == field
+		},
+		DecodeHook: mapstructure.ComposeDecodeHookFunc(
+			flow.ConfigurationUnmarshalerHook(),
+			mapstructure.TextUnmarshallerHookFunc(),
+			mapstructure.StringToTimeDurationHookFunc(),
+			mapstructure.StringToSliceHookFunc(","),
+		),
+	})
+	if err != nil {
+		return fmt.Errorf("unable to create configuration decoder: %w", err)
+	}
+	if err := decoder.Decode(rawConfig); err != nil {
+		return fmt.Errorf("unable to parse configuration: %w", err)
+	}
+
+	// Override with environment variables
+	for _, keyval := range os.Environ() {
+		kv := strings.SplitN(keyval, "=", 2)
+		if len(kv) != 2 {
+			continue
+		}
+		kk := strings.Split(kv[0], "_")
+		if len(kk) < 3 || kk[0] != "AKVORADO" || kk[1] != strings.ToUpper(component) {
+			continue
+		}
+		// From AKVORADO_CMP_SQUID_PURPLE_QUIRK=47, we
+		// build a map "squid -> purple -> quirk ->
+		// 47". From AKVORADO_CMP_SQUID_3_PURPLE=47, we
+		// build "squid[3] -> purple -> 47"
+		var rawConfig interface{}
+		rawConfig = kv[1]
+		for i := len(kk) - 1; i > 1; i-- {
+			if index, err := strconv.Atoi(kk[i]); err == nil {
+				newRawConfig := make([]interface{}, index+1)
+				newRawConfig[index] = rawConfig
+				rawConfig = newRawConfig
+			} else {
+				rawConfig = map[string]interface{}{
+					kk[i]: rawConfig,
+				}
+			}
+		}
+		if err := decoder.Decode(rawConfig); err != nil {
+			return fmt.Errorf("unable to parse override %q: %w", kv[0], err)
+		}
+	}
+
+	// Dump configuration if requested
+	if c.Dump {
+		output, err := yaml.Marshal(config)
+		if err != nil {
+			return fmt.Errorf("unable to dump configuration: %w", err)
+		}
+		out.Write([]byte("---\n"))
+		out.Write(output)
+		out.Write([]byte("\n"))
+	}
+
+	return nil
+}