add HashGenerator on requestid middleware

Former-commit-id: 8f59a46a3fecc538d6d3e624fc36f2c314c20bb6

middleware/requestid/requestid.go

@@ -1,6 +1,10 @@
 package requestid
 
 import (
+	"crypto/sha1"
+	"encoding/hex"
+	"net/http/httputil"
+
 	"github.com/kataras/iris/v12/context"
 
 	"github.com/google/uuid"
@@ -10,7 +14,7 @@ func init() {
 	context.SetHandlerName("iris/middleware/requestid.*", "iris.request.id")
 }
 
-const xRequestIDHeaderValue = "X-Request-Id"
+const xRequestIDHeaderKey = "X-Request-Id"
 
 // Generator defines the function which should extract or generate
 // a Request ID. See `DefaultGenerator` and `New` package-level functions.
@@ -23,8 +27,12 @@ type Generator func(ctx *context.Context) string
 //
 // See `Get` package-level function too.
 var DefaultGenerator Generator = func(ctx *context.Context) string {
-	id := ctx.GetHeader(xRequestIDHeaderValue)
+	id := ctx.ResponseWriter().Header().Get(xRequestIDHeaderKey)
+	if id != "" {
+		return id
+	}
 
+	id = ctx.GetHeader(xRequestIDHeaderKey)
 	if id == "" {
 		uid, err := uuid.NewRandom()
 		if err != nil {
@@ -33,12 +41,21 @@ var DefaultGenerator Generator = func(ctx *context.Context) string {
 		}
 
 		id = uid.String()
-		ctx.Header(xRequestIDHeaderValue, id)
 	}
 
+	ctx.Header(xRequestIDHeaderKey, id)
 	return id
 }
 
+// HashGenerator uses the request's hash to generate a fixed-length Request ID.
+// Note that one or many requests may contain the same ID, so it's not unique.
+func HashGenerator(includeBody bool) Generator {
+	return func(ctx *context.Context) string {
+		ctx.Header(xRequestIDHeaderKey, Hash(ctx, includeBody))
+		return DefaultGenerator(ctx)
+	}
+}
+
 // New returns a new request id middleware.
 // It optionally accepts an ID Generator.
 // The Generator can stop the handlers chain with an error or
@@ -81,3 +98,15 @@ func Get(ctx *context.Context) string {
 
 	return ""
 }
+
+// Hash returns the sha1 hash of the request.
+// It does not capture error, instead it returns an empty string.
+func Hash(ctx *context.Context, includeBody bool) string {
+	h := sha1.New()
+	b, err := httputil.DumpRequest(ctx.Request(), includeBody)
+	if err != nil {
+		return ""
+	}
+	h.Write(b)
+	return hex.EncodeToString(h.Sum(nil))
+}