first-commit

modules/cache/context.go

@@ -0,0 +1,43 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package cache
+
+import (
+	"context"
+	"time"
+)
+
+type cacheContextKeyType struct{}
+
+var cacheContextKey = cacheContextKeyType{}
+
+// contextCacheLifetime is the max lifetime of context cache.
+// Since context cache is used to cache data in a request level context, 5 minutes is enough.
+// If a context cache is used more than 5 minutes, it's probably abused.
+const contextCacheLifetime = 5 * time.Minute
+
+func WithCacheContext(ctx context.Context) context.Context {
+	if c := GetContextCache(ctx); c != nil {
+		return ctx
+	}
+	return context.WithValue(ctx, cacheContextKey, NewEphemeralCache(contextCacheLifetime))
+}
+
+func GetContextCache(ctx context.Context) *EphemeralCache {
+	c, _ := ctx.Value(cacheContextKey).(*EphemeralCache)
+	return c
+}
+
+// GetWithContextCache returns the cache value of the given key in the given context.
+// FIXME: in some cases, the "context cache" should not be used, because it has uncontrollable behaviors
+// For example, these calls:
+// * GetWithContextCache(TargetID) -> OtherCodeCreateModel(TargetID) -> GetWithContextCache(TargetID)
+// Will cause the second call is not able to get the correct created target.
+// UNLESS it is certain that the target won't be changed during the request, DO NOT use it.
+func GetWithContextCache[T, K any](ctx context.Context, groupKey string, targetKey K, f func(context.Context, K) (T, error)) (T, error) {
+	if c := GetContextCache(ctx); c != nil {
+		return GetWithEphemeralCache(ctx, c, groupKey, targetKey, f)
+	}
+	return f(ctx, targetKey)
+}