Backport #27000 by @wxiaoguang
This PR reduces the complexity of the system setting system.
It only needs one line to introduce a new option, and the option can be
used anywhere out-of-box.
It is still high-performant (and more performant) because the config
values are cached in the config system.
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Partially fix #23050
After #22294 merged, it always has a warning log like `cannot get
context cache` when starting up. This should not affect any real life
but it's annoying. This PR will fix the problem. That means when
starting up, getting the system settings will not try from the cache but
will read from the database directly.
---------
Co-authored-by: Lauris BH <lauris@nix.lv>
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.
Unfortunately, #22295 introduced a bug that when set a cached system
setting, it will not affect.
This PR make sure to remove the cache key when updating a system
setting.
Fix #22332
Change all license headers to comply with REUSE specification.
Fix #16132
Co-authored-by: flynnnnnnnnnn <flynnnnnnnnnn@github>
Co-authored-by: John Olheiser <john.olheiser@gmail.com>
