gocommon/tracing/config.go

package tracing

import (
	"fmt"
	"os"
	"strconv"
	"strings"

	"github.com/juju/errors"
	"gopkg.in/yaml.v3"

	"git.dev.m-and-m.ovh/mderasse/gocommon/convert"
	"git.dev.m-and-m.ovh/mderasse/gocommon/tracing/exporter/jaeger"
	"git.dev.m-and-m.ovh/mderasse/gocommon/tracing/exporter/zipkin"
)

// envPrefix is the prefix that will be used for any environnement variable used to configure the tracing system.
const envPrefix = "TRACING_"

// CONFIG_FILE is the default file that will be searched to apply configuration from the filesystem.
const defaultConfigFile = "conf/tracing.yaml"

// SECRET_NAME is the default name of the secret that will be searched in vault.
const defaultSecretName = "tracing"

// ConfigStruct represent the configuration of our tracing system.
type ConfigStruct struct {
	Attributes        map[string]string    `yaml:"attributes"`
	Enabled           bool                 `yaml:"enabled"`
	Exporter          ExporterName         `yaml:"exporter"`
	ServiceName       string               `yaml:"service_name"`
	ServiceVersion    string               `yaml:"service_version"`
	ServiceInstanceID string               `yaml:"service_instance_id"`
	JaegerConfig      *jaeger.ConfigStruct `yaml:"jaeger_config"`
	ZipkinConfig      *zipkin.ConfigStruct `yaml:"zipkin_config"`
}

func newDefaultConfig() *ConfigStruct {
	return &ConfigStruct{
		Enabled: false,
	}
}

func loadConfigFromVault(secret string) (*ConfigStruct, error) {
	_ = secret
	return nil, os.ErrNotExist
}

// loadConfigFromFile will read the given file and return a config struct.
func loadConfigFromFile(path string) (*ConfigStruct, error) {

	if _, err := os.Stat(path); errors.Is(err, os.ErrNotExist) {
		return nil, errors.Trace(err)
	}

	//nolint:gosec // we did compute the file path
	f, err := os.ReadFile(path)
	if err != nil {
		return nil, errors.Trace(err)
	}

	var config ConfigStruct

	if err := yaml.Unmarshal(f, &config); err != nil {
		return nil, errors.Trace(err)
	}

	return &config, nil
}

func loadConfig() (*ConfigStruct, error) {

	c, err := loadConfigFromVault(defaultSecretName)
	if err != nil && !errors.Is(err, os.ErrNotExist) {
		return nil, err
	} else if err == nil {
		return c, nil
	}

	c, err = loadConfigFromFile(defaultConfigFile)
	if err != nil && !errors.Is(err, os.ErrNotExist) {
		return nil, err
	} else if err == nil {
		return c, nil
	}

	return newDefaultConfig(), nil
}

// applyEnv will retrieve info from environment variable and overide those got by config / vault.
// validity of the value is not checked here and will be check in a IsValid method.
func (c *ConfigStruct) applyEnv() error {

	if v := os.Getenv(fmt.Sprintf("%s%s", envPrefix, "ENABLED")); v != "" {
		b, err := strconv.ParseBool(v)
		if err != nil {
			return errors.NewNotValid(err, fmt.Sprintf("Invalid %s%s environment variable. Should be a boolean", envPrefix, "ENABLED"))
		}
		c.Enabled = b
	}

	if v := os.Getenv(fmt.Sprintf("%s%s", envPrefix, "SERVICE_NAME")); v != "" {
		c.ServiceName = v
	}

	if v := os.Getenv(fmt.Sprintf("%s%s", envPrefix, "SERVICE_VERSION")); v != "" {
		c.ServiceVersion = v
	}

	if v := os.Getenv(fmt.Sprintf("%s%s", envPrefix, "SERVICE_INSTANCE_ID")); v != "" {
		c.ServiceInstanceID = v
	}

	if v := os.Getenv(fmt.Sprintf("%s%s", envPrefix, "EXPORTER")); v != "" {
		c.Exporter = ExporterName(v)
	}

	// Attributes
	if v := os.Getenv(fmt.Sprintf("%s%s", envPrefix, "ATTRIBUTES")); v != "" {
		if c.Attributes == nil {
			c.Attributes = make(map[string]string)
		}

		attributeParts := strings.Split(v, ",")
		for _, ap := range attributeParts {
			attributeKV := strings.SplitN(ap, ":", 2)
			if len(attributeKV) != 2 {
				return errors.NotValidf(fmt.Sprintf("Invalid attribute %s in environment variable. Should be a key1:value1,key2:value2 format", ap))
			}
			c.Attributes[attributeKV[0]] = attributeKV[1]
		}
	}

	return nil
}

// IsValid will check a config struct.
func (c *ConfigStruct) IsValid() error {

	if c.Enabled {
		if c.ServiceName == "" {
			return errors.NotValidf("ServiceName is empty")
		}

		if !c.Exporter.IsValid() {
			return errors.NotValidf("Invalid Exporter %s. Allowed values: %s", c.Exporter.String(), strings.Join(convert.StringerSliceToStringSlice(GetListExporterName()), ", "))
		}

		switch c.Exporter {
		case ExporterName_JAEGER:
			if c.JaegerConfig == nil {
				return errors.NotValidf("jaeger configuration is empty")
			}
			err := c.JaegerConfig.IsValid()
			if err != nil {
				return errors.Trace(err)
			}
		case ExporterName_ZIPKIN:
			if c.ZipkinConfig == nil {
				return errors.NotValidf("zipkin configuration is empty")
			}
			err := c.ZipkinConfig.IsValid()
			if err != nil {
				return errors.Trace(err)
			}
		default:
			return errors.NotValidf("Exporter not handled")
		}
	}

	return nil
}