forgejo/services
Lunny Xiao bd820aa9c5
Add context cache as a request level cache (#22294)
To avoid duplicated load of the same data in an HTTP request, we can set
a context cache to do that. i.e. Some pages may load a user from a
database with the same id in different areas on the same page. But the
code is hidden in two different deep logic. How should we share the
user? As a result of this PR, now if both entry functions accept
`context.Context` as the first parameter and we just need to refactor
`GetUserByID` to reuse the user from the context cache. Then it will not
be loaded twice on an HTTP request.

But of course, sometimes we would like to reload an object from the
database, that's why `RemoveContextData` is also exposed.

The core context cache is here. It defines a new context
```go
type cacheContext struct {
	ctx  context.Context
	data map[any]map[any]any
        lock sync.RWMutex
}

var cacheContextKey = struct{}{}

func WithCacheContext(ctx context.Context) context.Context {
	return context.WithValue(ctx, cacheContextKey, &cacheContext{
		ctx:  ctx,
		data: make(map[any]map[any]any),
	})
}
```

Then you can use the below 4 methods to read/write/del the data within
the same context.

```go
func GetContextData(ctx context.Context, tp, key any) any
func SetContextData(ctx context.Context, tp, key, value any)
func RemoveContextData(ctx context.Context, tp, key any)
func GetWithContextCache[T any](ctx context.Context, cacheGroupKey string, cacheTargetID any, f func() (T, error)) (T, error)
```

Then let's take a look at how `system.GetString` implement it.

```go
func GetSetting(ctx context.Context, key string) (string, error) {
	return cache.GetWithContextCache(ctx, contextCacheKey, key, func() (string, error) {
		return cache.GetString(genSettingCacheKey(key), func() (string, error) {
			res, err := GetSettingNoCache(ctx, key)
			if err != nil {
				return "", err
			}
			return res.SettingValue, nil
		})
	})
}
```

First, it will check if context data include the setting object with the
key. If not, it will query from the global cache which may be memory or
a Redis cache. If not, it will get the object from the database. In the
end, if the object gets from the global cache or database, it will be
set into the context cache.

An object stored in the context cache will only be destroyed after the
context disappeared.
2023-02-15 21:37:34 +08:00
..
actions Add context cache as a request level cache (#22294) 2023-02-15 21:37:34 +08:00
agit Rename almost all Ctx functions (#22071) 2022-12-10 10:46:31 +08:00
asymkey Add context cache as a request level cache (#22294) 2023-02-15 21:37:34 +08:00
attachment Add API management for issue/pull and comment attachments (#21783) 2022-12-09 14:35:56 +08:00
auth Add context cache as a request level cache (#22294) 2023-02-15 21:37:34 +08:00
automerge Improve trace logging for pulls and processes (#22633) 2023-02-03 18:11:48 -05:00
context Support org/user level projects (#22235) 2023-01-20 19:42:33 +08:00
convert Add context cache as a request level cache (#22294) 2023-02-15 21:37:34 +08:00
cron Add Cargo package registry (#21888) 2023-02-05 18:12:31 +08:00
externalaccount Implement FSFE REUSE for golang files (#21840) 2022-11-27 18:20:29 +00:00
forms Pull Requests: setting to allow edits by maintainers by default, tweak UI (#22862) 2023-02-13 14:09:52 +08:00
gitdiff Refactor git command package to improve security and maintainability (#22678) 2023-02-04 10:30:43 +08:00
issue Webhooks: for issue close/reopen action, add commit ID that caused it (#22583) 2023-01-24 23:47:53 -05:00
lfs Use context parameter in models/git (#22367) 2023-01-09 11:50:54 +08:00
mailer fix permission check for creating comment while mail (#22524) 2023-01-28 17:28:55 +08:00
markup Implement FSFE REUSE for golang files (#21840) 2022-11-27 18:20:29 +00:00
migrations Prevent duplicate labels when importing more than 99 (#22591) 2023-01-24 19:44:55 +00:00
mirror Use proxy for pull mirror (#22771) 2023-02-11 08:39:50 +08:00
org Implement FSFE REUSE for golang files (#21840) 2022-11-27 18:20:29 +00:00
packages Use import of OCI structs (#22765) 2023-02-06 10:07:09 +00:00
pull Add context cache as a request level cache (#22294) 2023-02-15 21:37:34 +08:00
release Add context cache as a request level cache (#22294) 2023-02-15 21:37:34 +08:00
repository Add context cache as a request level cache (#22294) 2023-02-15 21:37:34 +08:00
task Implement FSFE REUSE for golang files (#21840) 2022-11-27 18:20:29 +00:00
user Add context cache as a request level cache (#22294) 2023-02-15 21:37:34 +08:00
webhook Add context cache as a request level cache (#22294) 2023-02-15 21:37:34 +08:00
wiki Improve utils of slices (#22379) 2023-01-11 13:31:16 +08:00