1 files changed, 121 insertions, 0 deletions
diff --git a/modules/caddyhttp/tracing/module.go b/modules/caddyhttp/tracing/module.go
new file mode 100644
index 0000000..7cce669
--- /dev/null
+++ b/modules/caddyhttp/tracing/module.go
@@ -0,0 +1,121 @@
+package tracing
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/caddyserver/caddy/v2"
+	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
+	"github.com/caddyserver/caddy/v2/caddyconfig/httpcaddyfile"
+	"github.com/caddyserver/caddy/v2/modules/caddyhttp"
+	"go.uber.org/zap"
+)
+
+func init() {
+	caddy.RegisterModule(Tracing{})
+	httpcaddyfile.RegisterHandlerDirective("tracing", parseCaddyfile)
+}
+
+// Tracing implements an HTTP handler that adds support for distributed tracing,
+// using OpenTelemetry. This module is responsible for the injection and
+// propagation of the trace context. Configure this module via environment
+// variables (see https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/sdk-environment-variables.md).
+// Some values can be overwritten in the configuration file.
+type Tracing struct {
+	// SpanName is a span name. It should follow the naming guidelines here:
+	// https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/api.md#span
+	SpanName string `json:"span"`
+
+	// otel implements opentelemetry related logic.
+	otel openTelemetryWrapper
+
+	logger *zap.Logger
+}
+
+// CaddyModule returns the Caddy module information.
+func (Tracing) CaddyModule() caddy.ModuleInfo {
+	return caddy.ModuleInfo{
+		ID:  "http.handlers.tracing",
+		New: func() caddy.Module { return new(Tracing) },
+	}
+}
+
+// Provision implements caddy.Provisioner.
+func (ot *Tracing) Provision(ctx caddy.Context) error {
+	ot.logger = ctx.Logger(ot)
+
+	var err error
+	ot.otel, err = newOpenTelemetryWrapper(ctx, ot.SpanName)
+
+	return err
+}
+
+// Cleanup implements caddy.CleanerUpper and closes any idle connections. It
+// calls Shutdown method for a trace provider https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/sdk.md#shutdown.
+func (ot *Tracing) Cleanup() error {
+	if err := ot.otel.cleanup(ot.logger); err != nil {
+		return fmt.Errorf("tracerProvider shutdown: %w", err)
+	}
+	return nil
+}
+
+// ServeHTTP implements caddyhttp.MiddlewareHandler.
+func (ot *Tracing) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
+	return ot.otel.ServeHTTP(w, r, next)
+}
+
+// UnmarshalCaddyfile sets up the module from Caddyfile tokens. Syntax:
+//
+//     tracing {
+//         [span <span_name>]
+//     }
+//
+func (ot *Tracing) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
+	setParameter := func(d *caddyfile.Dispenser, val *string) error {
+		if d.NextArg() {
+			*val = d.Val()
+		} else {
+			return d.ArgErr()
+		}
+		if d.NextArg() {
+			return d.ArgErr()
+		}
+		return nil
+	}
+
+	// paramsMap is a mapping between "string" parameter from the Caddyfile and its destination within the module
+	paramsMap := map[string]*string{
+		"span": &ot.SpanName,
+	}
+
+	for d.Next() {
+		args := d.RemainingArgs()
+		if len(args) > 0 {
+			return d.ArgErr()
+		}
+
+		for d.NextBlock(0) {
+			if dst, ok := paramsMap[d.Val()]; ok {
+				if err := setParameter(d, dst); err != nil {
+					return err
+				}
+			} else {
+				return d.ArgErr()
+			}
+		}
+	}
+	return nil
+}
+
+func parseCaddyfile(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, error) {
+	var m Tracing
+	err := m.UnmarshalCaddyfile(h.Dispenser)
+	return &m, err
+}
+
+// Interface guards
+var (
+	_ caddy.Provisioner           = (*Tracing)(nil)
+	_ caddyhttp.MiddlewareHandler = (*Tracing)(nil)
+	_ caddyfile.Unmarshaler       = (*Tracing)(nil)
+)