add a new simple, builtin requestid middleware (makes use of the Context.SetID/GetID methods too)

Former-commit-id: d46bce7c1964adada01934aa95daf389c141defc

middleware/requestid/requestid.go

@@ -0,0 +1,82 @@
+package requestid
+
+import (
+	"github.com/kataras/iris/v12/context"
+
+	"github.com/google/uuid"
+)
+
+func init() {
+	context.SetHandlerName("iris/middleware/requestid.*", "iris.request.id")
+}
+
+const xRequestIDHeaderValue = "X-Request-ID"
+
+// Generator defines the function which should extract or generate
+// a Request ID. See `DefaultGenerator` and `New` package-level functions.
+type Generator func(ctx context.Context) string
+
+// DefaultGenerator is the default `Generator` that is used
+// when nil is passed on `New` package-level function.
+// It extracts the ID from the "X-Request-ID" request header value
+// or, if missing, it generates a new UUID(v4) and sets the header and context value.
+//
+// See `Get` package-level function too.
+var DefaultGenerator Generator = func(ctx context.Context) string {
+	id := ctx.GetHeader(xRequestIDHeaderValue)
+
+	if id == "" {
+		uid, err := uuid.NewRandom()
+		if err != nil {
+			ctx.StopWithStatus(500)
+			return ""
+		}
+
+		id = uid.String()
+		ctx.Header(xRequestIDHeaderValue, id)
+	}
+
+	return id
+}
+
+// New returns a new request id middleware.
+// It accepts an ID Generator.
+// The Generator can stop the handlers chain with an error or
+// return a valid ID (string).
+// If it's nil then the `DefaultGenerator` will be used instead.
+func New(gen Generator) context.Handler {
+	if gen == nil {
+		gen = DefaultGenerator
+	}
+
+	return func(ctx context.Context) {
+		if Get(ctx) != "" {
+			ctx.Next()
+			return
+		}
+
+		id := gen(ctx)
+		if ctx.IsStopped() {
+			// ctx.Next checks that
+			// but we don't want to call SetID if generator failed.
+			return
+		}
+
+		ctx.SetID(id)
+		ctx.Next()
+	}
+}
+
+// Get returns the Request ID or empty string.
+//
+// A shortcut of `context.GetID().(string)`.
+func Get(ctx context.Context) string {
+	v := ctx.GetID()
+	if v != nil {
+		if id, ok := v.(string); ok {
+			return id
+		}
+	}
+
+	return ""
+}