feat: added configuration center function (#3035)

Co-authored-by: aiden.ma <Aiden.ma@yijinin.com>

core/configcenter/configurator.go

@@ -0,0 +1,205 @@
+package configurator
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+	"strings"
+	"sync"
+	"sync/atomic"
+
+	"github.com/zeromicro/go-zero/core/configcenter/subscriber"
+	"github.com/zeromicro/go-zero/core/logx"
+	"github.com/zeromicro/go-zero/core/mapping"
+	"github.com/zeromicro/go-zero/core/threading"
+)
+
+var (
+	errorEmptyConfig         = errors.New("empty config value")
+	errorMissUnmarshalerType = errors.New("miss unmarshaler type")
+)
+
+// Configurator is the interface for configuration center.
+type Configurator[T any] interface {
+	// GetConfig returns the subscription value.
+	GetConfig() (T, error)
+	// AddListener adds a listener to the subscriber.
+	AddListener(listener func())
+}
+
+type (
+	// Config is the configuration for Configurator.
+	Config struct {
+		// Type is the value type, yaml, json or toml.
+		Type string `json:",default=yaml,options=[yaml,json,toml]"`
+		// Log indicates whether to log the configuration.
+		Log bool `json:",default=ture"`
+	}
+
+	configCenter[T any] struct {
+		conf        Config
+		unmarshaler LoaderFn
+
+		subscriber subscriber.Subscriber
+
+		listeners []func()
+		lock      sync.Mutex
+		snapshot  atomic.Value
+	}
+
+	value[T any] struct {
+		data        string
+		marshalData T
+		err         error
+	}
+)
+
+// Configurator is the interface for configuration center.
+var _ Configurator[any] = (*configCenter[any])(nil)
+
+// MustNewConfigCenter returns a Configurator, exits on errors.
+func MustNewConfigCenter[T any](c Config, subscriber subscriber.Subscriber) Configurator[T] {
+	cc, err := NewConfigCenter[T](c, subscriber)
+	logx.Must(err)
+
+	return cc
+}
+
+// NewConfigCenter returns a Configurator.
+func NewConfigCenter[T any](c Config, subscriber subscriber.Subscriber) (Configurator[T], error) {
+	unmarshaler, ok := Unmarshaler(strings.ToLower(c.Type))
+	if !ok {
+		return nil, fmt.Errorf("unknown format: %s", c.Type)
+	}
+
+	cc := &configCenter[T]{
+		conf:        c,
+		unmarshaler: unmarshaler,
+		subscriber:  subscriber,
+		listeners:   nil,
+		lock:        sync.Mutex{},
+		snapshot:    atomic.Value{},
+	}
+
+	if err := cc.loadConfig(); err != nil {
+		return nil, err
+	}
+
+	if err := cc.subscriber.AddListener(cc.onChange); err != nil {
+		return nil, err
+	}
+
+	if _, err := cc.GetConfig(); err != nil {
+		return nil, err
+	}
+
+	return cc, nil
+}
+
+// AddListener adds listener to s.
+func (c *configCenter[T]) AddListener(listener func()) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.listeners = append(c.listeners, listener)
+}
+
+// GetConfig return structured config.
+func (c *configCenter[T]) GetConfig() (T, error) {
+	var r T
+	v := c.value()
+	if v == nil || len(v.data) < 1 {
+		return r, errorEmptyConfig
+	}
+
+	return v.marshalData, v.err
+}
+
+// Value returns the subscription value.
+func (c *configCenter[T]) Value() string {
+	v := c.value()
+	if v == nil {
+		return ""
+	}
+	return v.data
+}
+
+func (c *configCenter[T]) loadConfig() error {
+	v, err := c.subscriber.Value()
+	if err != nil {
+		if c.conf.Log {
+			logx.Errorf("ConfigCenter loads changed configuration, error: %v", err)
+		}
+		return err
+	}
+
+	if c.conf.Log {
+		logx.Infof("ConfigCenter loads changed configuration, content [%s]", v)
+	}
+
+	c.snapshot.Store(c.genValue(v))
+	return nil
+}
+
+func (c *configCenter[T]) onChange() {
+	_ = c.loadConfig()
+
+	c.lock.Lock()
+	listeners := make([]func(), len(c.listeners))
+	copy(listeners, c.listeners)
+	c.lock.Unlock()
+
+	for _, l := range listeners {
+		threading.GoSafe(l)
+	}
+}
+
+func (c *configCenter[T]) value() *value[T] {
+	content := c.snapshot.Load()
+	if content == nil {
+		return nil
+	}
+	return content.(*value[T])
+}
+
+func (c *configCenter[T]) genValue(data string) *value[T] {
+	v := &value[T]{
+		data: data,
+	}
+	if len(data) <= 0 {
+		return v
+	}
+
+	t := reflect.TypeOf(v.marshalData)
+	// if the type is nil, it means that the user has not set the type of the configuration.
+	if t == nil {
+		v.err = errorMissUnmarshalerType
+		return v
+	}
+
+	t = mapping.Deref(t)
+
+	switch t.Kind() {
+	case reflect.Struct, reflect.Array, reflect.Slice:
+		err := c.unmarshaler([]byte(data), &v.marshalData)
+		if err != nil {
+			v.err = err
+			if c.conf.Log {
+				logx.Errorf("ConfigCenter unmarshal configuration failed, err: %+v, content [%s]", err.Error(), data)
+			}
+		}
+	case reflect.String:
+		if str, ok := any(data).(T); ok {
+			v.marshalData = str
+		} else {
+			v.err = errorMissUnmarshalerType
+		}
+	default:
+		if c.conf.Log {
+			logx.Errorf("ConfigCenter unmarshal configuration missing unmarshaler for type: %s, content [%s]",
+				t.Kind(), data)
+		}
+		v.err = errorMissUnmarshalerType
+	}
+
+	return v
+}