Adding upstream version 2.52.6.

Signed-off-by: Daniel Baumann <daniel@debian.org>

middleware/idempotency/idempotency.go

@@ -0,0 +1,153 @@
+package idempotency
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/gofiber/fiber/v2"
+	"github.com/gofiber/fiber/v2/log"
+	"github.com/gofiber/fiber/v2/utils"
+)
+
+// Inspired by https://datatracker.ietf.org/doc/html/draft-ietf-httpapi-idempotency-key-header-02
+// and https://github.com/penguin-statistics/backend-next/blob/f2f7d5ba54fc8a58f168d153baa17b2ad4a14e45/internal/pkg/middlewares/idempotency.go
+
+type localsKeys string
+
+const (
+	localsKeyIsFromCache   localsKeys = "idempotency_isfromcache"
+	localsKeyWasPutToCache localsKeys = "idempotency_wasputtocache"
+)
+
+func IsFromCache(c *fiber.Ctx) bool {
+	return c.Locals(localsKeyIsFromCache) != nil
+}
+
+func WasPutToCache(c *fiber.Ctx) bool {
+	return c.Locals(localsKeyWasPutToCache) != nil
+}
+
+func New(config ...Config) fiber.Handler {
+	// Set default config
+	cfg := configDefault(config...)
+
+	keepResponseHeadersMap := make(map[string]struct{}, len(cfg.KeepResponseHeaders))
+	for _, h := range cfg.KeepResponseHeaders {
+		keepResponseHeadersMap[strings.ToLower(h)] = struct{}{}
+	}
+
+	maybeWriteCachedResponse := func(c *fiber.Ctx, key string) (bool, error) {
+		if val, err := cfg.Storage.Get(key); err != nil {
+			return false, fmt.Errorf("failed to read response: %w", err)
+		} else if val != nil {
+			var res response
+			if _, err := res.UnmarshalMsg(val); err != nil {
+				return false, fmt.Errorf("failed to unmarshal response: %w", err)
+			}
+
+			_ = c.Status(res.StatusCode)
+
+			for header, vals := range res.Headers {
+				for _, val := range vals {
+					c.Context().Response.Header.Add(header, val)
+				}
+			}
+
+			if len(res.Body) != 0 {
+				if err := c.Send(res.Body); err != nil {
+					return true, err
+				}
+			}
+
+			_ = c.Locals(localsKeyIsFromCache, true)
+
+			return true, nil
+		}
+
+		return false, nil
+	}
+
+	return func(c *fiber.Ctx) error {
+		// Don't execute middleware if Next returns true
+		if cfg.Next != nil && cfg.Next(c) {
+			return c.Next()
+		}
+
+		// Don't execute middleware if the idempotency key is empty
+		key := utils.CopyString(c.Get(cfg.KeyHeader))
+		if key == "" {
+			return c.Next()
+		}
+
+		// Validate key
+		if err := cfg.KeyHeaderValidate(key); err != nil {
+			return err
+		}
+
+		// First-pass: if the idempotency key is in the storage, get and return the response
+		if ok, err := maybeWriteCachedResponse(c, key); err != nil {
+			return fmt.Errorf("failed to write cached response at fastpath: %w", err)
+		} else if ok {
+			return nil
+		}
+
+		if err := cfg.Lock.Lock(key); err != nil {
+			return fmt.Errorf("failed to lock: %w", err)
+		}
+		defer func() {
+			if err := cfg.Lock.Unlock(key); err != nil {
+				log.Errorf("[IDEMPOTENCY] failed to unlock key %q: %v", key, err)
+			}
+		}()
+
+		// Lock acquired. If the idempotency key now is in the storage, get and return the response
+		if ok, err := maybeWriteCachedResponse(c, key); err != nil {
+			return fmt.Errorf("failed to write cached response while locked: %w", err)
+		} else if ok {
+			return nil
+		}
+
+		// Execute the request handler
+		if err := c.Next(); err != nil {
+			// If the request handler returned an error, return it and skip idempotency
+			return err
+		}
+
+		// Construct response
+		res := &response{
+			StatusCode: c.Response().StatusCode(),
+
+			Body: utils.CopyBytes(c.Response().Body()),
+		}
+		{
+			headers := c.GetRespHeaders()
+			if cfg.KeepResponseHeaders == nil {
+				// Keep all
+				res.Headers = headers
+			} else {
+				// Filter
+				res.Headers = make(map[string][]string)
+				for h := range headers {
+					if _, ok := keepResponseHeadersMap[utils.ToLower(h)]; ok {
+						res.Headers[h] = headers[h]
+					}
+				}
+			}
+		}
+
+		// Marshal response
+		bs, err := res.MarshalMsg(nil)
+		if err != nil {
+			return fmt.Errorf("failed to marshal response: %w", err)
+		}
+
+		// Store response
+		if err := cfg.Storage.Set(key, bs, cfg.Lifetime); err != nil {
+			return fmt.Errorf("failed to save response: %w", err)
+		}
+
+		_ = c.Locals(localsKeyWasPutToCache, true)
+
+		return nil
+	}
+}