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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 <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)
)
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