package tracing import ( "fmt" "net/http" "go.uber.org/zap" "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" ) 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() 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 ] // } 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) )