Backend: Adding OTLP Configuration

pkg/backends/otlp/client.go

@@ -3,7 +3,11 @@ package otlp
 import (
 	"context"
 
+	"github.com/sirupsen/logrus"
+	"github.com/spf13/viper"
+
 	"github.com/atlassian/gostatsd"
+	"github.com/atlassian/gostatsd/pkg/transport"
 )
 
 const (
@@ -13,12 +17,19 @@ const (
 // Client contains additional meta data in order
 // to export values as OTLP metrics.
 // The zero value is not safe to use.
-type Client struct {
-	resources []string
-}
+type Client struct{}
 
 var _ gostatsd.Backend = (*Client)(nil)
 
+func NewClientFromViper(v *viper.Viper, logger logrus.FieldLogger, pool *transport.TransportPool) (gostatsd.Backend, error) {
+	_, err := NewConfig(v)
+	if err != nil {
+		return nil, err
+	}
+
+	return Client{}, nil
+}
+
 func (Client) Name() string { return namedBackend }
 
 func (Client) SendEvent(ctx context.Context, e *gostatsd.Event) error {

pkg/backends/otlp/config.go

@@ -0,0 +1,89 @@
+package otlp
+
+import (
+	"errors"
+	"runtime"
+
+	"github.com/spf13/viper"
+	"go.uber.org/multierr"
+)
+
+const (
+	ConversionAsGauge     = "AsGauge"
+	ConversionAsHistogram = "AsHistogram"
+)
+
+type Config struct {
+	// Endpoint (Required) is the FQDN with path for the metrics ingestion endpoint
+	Endpoint string `mapstructure:"endpoint"`
+	// MaxRequests (Optional, default: cpu.count * 2) is the upper limit on the number of inflight requests
+	MaxRequests int `mapstructure:"max_requests"`
+	// ResourceKeys (Optional) is used to extract values from provided tags
+	// to apply to all values within a resource instead within each attribute.
+	// Strongly encouraged to allow down stream consumers to
+	// process based on values defined at the top level resource.
+	ResourceKeys []string `mapstructure:"resource_keys"`
+	// TimerConversion (Optional, Default: AsGauge) determines if a timers are emitted as one of the following:
+	// - AsGauges emits each calcauted value (min, max, sum, count, upper, upper_99, etc...) as a guage value
+	// - AsHistograms each timer is set as an empty bucket histogram with only Min, Max, Sum, and Count set
+	TimerConversion string `mapstructure:"timer_conversion"`
+	// HistogramConversion (Optional, Default: AsGauge) determines how a GoStatsD histogram should be converted into OTLP.
+	// The allowed values for this are:
+	// - AsGauges: sends each bucket count (including +inf) as a guage value and the bucket boundry as a tag
+	// - AsHistogram: sends each histogram as a single Histogram value with bucket and statistics calculated.
+	HistogramConversion string `mapstructure:"histogram_conversion"`
+	// Transport (Optional, Default: "default") is used to reference to configured transport
+	// to be used for this backend
+	Transport string `mapstructure:"transport"`
+	// UserAgent (Optional, default: "gostatsd") allows you to set the
+	// user agent header when making requests.
+	UserAgent string `mapstructure:"user_agent"`
+}
+
+func newDefaultConfig() Config {
+	return Config{
+		Transport:           "default",
+		MaxRequests:         runtime.NumCPU() * 2,
+		TimerConversion:     "AsGauge",
+		HistogramConversion: "AsGauge",
+		UserAgent:           "gostatsd",
+	}
+}
+
+func NewConfig(v *viper.Viper) (*Config, error) {
+	cfg := newDefaultConfig()
+	if err := v.Unmarshal(&cfg); err != nil {
+		return nil, err
+	}
+	if err := cfg.Validate(); err != nil {
+		return nil, err
+	}
+	return &cfg, nil
+}
+
+func (c Config) Validate() (errs error) {
+	if c.Endpoint == "" {
+		errs = multierr.Append(errs, errors.New("no endpoint defined"))
+	}
+	if c.MaxRequests <= 0 {
+		errs = multierr.Append(errs, errors.New("max request must be a positive value"))
+	}
+	if c.Transport == "" {
+		errs = multierr.Append(errs, errors.New("no transport defined"))
+	}
+
+	conversion := map[string]struct{}{
+		ConversionAsGauge:     {},
+		ConversionAsHistogram: {},
+	}
+
+	if _, ok := conversion[c.TimerConversion]; !ok {
+		errs = multierr.Append(errs, errors.New(`time conversion must be one of ["AsGauge", "AsHistogram"]`))
+	}
+
+	if _, ok := conversion[c.HistogramConversion]; !ok {
+		errs = multierr.Append(errs, errors.New(`histogram conversion must be one of ["AsGauge", "AsHistogram"]`))
+	}
+
+	return errs
+}

pkg/backends/otlp/config_test.go

@@ -0,0 +1,70 @@
+package otlp
+
+import (
+	"testing"
+
+	"github.com/spf13/viper"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewConfig(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range []struct {
+		name   string
+		v      *viper.Viper
+		expect *Config
+		errVal string
+	}{
+		{
+			name:   "empty configuration",
+			v:      viper.New(),
+			expect: nil,
+			errVal: "no endpoint defined",
+		},
+		{
+			name: "min configuration defined",
+			v: func() *viper.Viper {
+				v := viper.New()
+				v.SetDefault("endpoint", "http://local")
+				v.SetDefault("max_requests", 1)
+				return v
+			}(),
+			expect: &Config{
+				Endpoint:            "http://local",
+				MaxRequests:         1,
+				TimerConversion:     "AsGauge",
+				HistogramConversion: "AsGauge",
+				Transport:           "default",
+				UserAgent:           "gostatsd",
+			},
+			errVal: "",
+		},
+		{
+			name: "invalid options",
+			v: func() *viper.Viper {
+				v := viper.New()
+				v.SetDefault("max_requests", 0)
+				v.SetDefault("transport", "")
+				v.SetDefault("timer_conversion", "values")
+				v.SetDefault("histogram_conversion", "values")
+				return v
+			}(),
+			expect: nil,
+			errVal: "no endpoint defined; max request must be a positive value; no transport defined; time conversion must be one of [\"AsGauge\", \"AsHistogram\"]; histogram conversion must be one of [\"AsGauge\", \"AsHistogram\"]",
+		},
+	} {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			cfg, err := NewConfig(tc.v)
+			assert.Equal(t, tc.expect, cfg, "Must match the expected configuration")
+			if tc.errVal != "" {
+				assert.EqualError(t, err, tc.errVal, "Must match the expected error")
+			} else {
+				assert.NoError(t, err, "Must not error")
+			}
+		})
+	}
+}