[#12] tracing: Add tracing package

Add tracing config, implementation and setup

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/tracing/config.go

@@ -0,0 +1,74 @@
+package tracing
+
+import "fmt"
+
+// Exporter is type of tracing target.
+type Exporter string
+
+const (
+	Stdout   Exporter = "stdout"
+	OTLPgRPC Exporter = "otlp_grpc"
+)
+
+type Config struct {
+	// Enabled is true, if tracing enabled.
+	Enabled bool
+	// Exporter is collector type.
+	Exporter Exporter
+	// Endpoint is collector endpoint for OTLP exporters.
+	Endpoint string
+
+	// Service is service name that will be used in tracing.
+	// Mandatory.
+	Service string
+	// InstanceID is identity of service instance.
+	// Optional.
+	InstanceID string
+	// Version is version of service instance.
+	// Optional.
+	Version string
+}
+
+func (c *Config) validate() error {
+	if !c.Enabled {
+		return nil
+	}
+
+	if c.Exporter != Stdout && c.Exporter != OTLPgRPC {
+		return fmt.Errorf("tracing config error: unknown exporter '%s', valid values are %v",
+			c.Exporter, []string{string(Stdout), string(OTLPgRPC)})
+	}
+
+	if len(c.Service) == 0 {
+		return fmt.Errorf("tracing config error: service name must be specified")
+	}
+
+	if c.Exporter == OTLPgRPC && len(c.Endpoint) == 0 {
+		return fmt.Errorf("tracing config error: exporter '%s' requires endpoint", c.Exporter)
+	}
+
+	return nil
+}
+
+func (c *Config) hasChange(other *Config) bool {
+	if !c.Enabled && !other.Enabled {
+		return false
+	}
+	if c.Enabled != other.Enabled {
+		return true
+	}
+
+	if c.Exporter == Stdout && other.Exporter == Stdout {
+		return !c.serviceInfoEqual(other)
+	}
+
+	return c.Exporter != other.Exporter ||
+		c.Endpoint != other.Endpoint ||
+		!c.serviceInfoEqual(other)
+}
+
+func (c *Config) serviceInfoEqual(other *Config) bool {
+	return c.Service == other.Service &&
+		c.InstanceID == other.InstanceID &&
+		c.Version == other.Version
+}