feat: support degradation config for Kitex client

README.md

@@ -283,6 +283,27 @@ The echo method uses the following configuration (0.3, 100) and other methods us
 }
 ```
 
+##### Degradation: Category=degradation
+
+[JSON Schema](https://github.com/cloudwego/kitex/blob/develop/pkg/circuitbreak/item_circuit_breaker.go#L30)
+
+| Variable   | Introduction                       |
+|------------|------------------------------------|
+| enable     | Whether to enable degradation      |
+| percentage | The percentage of dropped requests | 
+
+Example：
+
+> configPath: /KitexConfig/ClientName/ServiceName/degradation
+
+```json
+{
+  "enable": true,
+  "percentage": 30
+}
+```
+Note: Degradation is not enabled by default.
+
 ### More Info
 
 Refer to [example](https://github.com/kitex-contrib/config-zookeeper/tree/main/example) for more usage.

README_CN.md

@@ -283,7 +283,26 @@ echo 方法使用下面的配置（0.3, 100），其他方法使用全局默认
 }
 ```
 
+##### 降级: Category=degradation
 
+[JSON Schema](https://github.com/cloudwego/kitex/blob/develop/pkg/circuitbreak/item_circuit_breaker.go#L30)
+
+| 参数         | 说明       |
+|------------|----------|
+| enable     | 是否开启降级策略 |
+| percentage | 丢弃请求的比例  | 
+
+例子：
+
+> configPath: /KitexConfig/ClientName/ServiceName/degradation
+
+```json
+{
+  "enable": true,
+  "percentage": 30
+}
+```
+注：默认不开启降级（enable为false）
 
 ### 更多信息
 

client/degradation.go

@@ -0,0 +1,57 @@
+package client
+
+import (
+	"context"
+
+	"github.com/cloudwego/kitex/client"
+	"github.com/cloudwego/kitex/pkg/klog"
+	"github.com/kitex-contrib/config-zookeeper/pkg/degradation"
+	"github.com/kitex-contrib/config-zookeeper/utils"
+	"github.com/kitex-contrib/config-zookeeper/zookeeper"
+)
+
+func WithDegradation(dest, src string, zookeeperClient zookeeper.Client, opts utils.Options) []client.Option {
+    param, err := zookeeperClient.ClientConfigParam(&zookeeper.ConfigParamConfig{
+       Category:          degradationConfigName,
+       ServerServiceName: dest,
+       ClientServiceName: src,
+    })
+    if err != nil {
+       panic(err)
+    }
+
+	for _, f := range opts.ZookeeperCustomFunctions {
+		f(&param)
+	}
+
+	uid := zookeeper.GetUniqueID()
+	path := param.Prefix + "/" + param.Path
+	container := initDegradation(path, uid, dest, zookeeperClient)
+	return []client.Option{
+		client.WithACLRules(container.GetAclRule()),
+		client.WithCloseCallbacks(func() error {
+			// cancel the configuration listener when client is closed.
+			zookeeperClient.DeregisterConfig(path, uid)
+			return nil
+		}),
+	}
+}
+
+func initDegradation(path string, uniqueID int64, dest string, zookeeperClient zookeeper.Client) *degradation.Container {
+	container := degradation.NewContainer()
+	onChangeCallback := func(restoreDefault bool, data string, parser zookeeper.ConfigParser) {
+		config := &degradation.Config{}
+		if !restoreDefault {
+			err := parser.Decode(data, config)
+			if err != nil {
+				klog.Warnf("[zookeeper] %s server etcd degradation config: unmarshal data %s failed: %s, skip...", path, data, err)
+				return
+			}
+		}
+		container.NotifyPolicyChange(config)
+	}
+
+	zookeeperClient.RegisterConfigCallback(context.Background(), path, uniqueID, onChangeCallback)
+
+	return container
+}

client/suite.go

@@ -24,6 +24,7 @@ const (
 	retryConfigName          = "retry"
 	rpcTimeoutConfigName     = "rpc_timeout"
 	circuitBreakerConfigName = "circuit_break"
+	degradationConfigName    = "degradation"
 )
 
 // ZookeeperClientSuite zookeeper client config suite, configure retry timeout limit and circuitbreak dynamically from zookeeper.
@@ -53,5 +54,6 @@ func (s *ZookeeperClientSuite) Options() []client.Option {
 	opts = append(opts, WithRetryPolicy(s.service, s.client, s.zookeeperClient, s.opts)...)
 	opts = append(opts, WithRPCTimeout(s.service, s.client, s.zookeeperClient, s.opts)...)
 	opts = append(opts, WithCircuitBreaker(s.service, s.client, s.zookeeperClient, s.opts)...)
+	opts = append(opts, WithDegradation(s.service, s.client, s.zookeeperClient, s.opts)...)
 	return opts
 }

pkg/degradation/item_degradation.go

@@ -0,0 +1,84 @@
+// Copyright 2024 CloudWeGo Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package degradation
+
+import (
+	"context"
+	"errors"
+	"sync/atomic"
+
+	"github.com/bytedance/gopkg/lang/fastrand"
+	"github.com/cloudwego/configmanager/iface"
+	"github.com/cloudwego/kitex/pkg/acl"
+)
+
+var errRejected = errors.New("rejected by client degradation config")
+
+var defaultConfig = &Config{
+	Enable:     false,
+	Percentage: 0,
+}
+
+type Config struct {
+	Enable     bool `json:"enable"`
+	Percentage int  `json:"percentage"`
+}
+
+// DeepCopy returns a copy of the current Config
+func (c *Config) DeepCopy() iface.ConfigValueItem {
+	if c == nil {
+       return nil
+    }
+	result := &Config{
+		Enable:     c.Enable,
+		Percentage: c.Percentage,
+	}
+	return result
+}
+
+// EqualsTo returns true if the current Config equals to the other Config
+func (c *Config) EqualsTo(other iface.ConfigValueItem) bool {
+	o := other.(*Config)
+	return c.Enable == o.Enable && c.Percentage == o.Percentage
+}
+
+// Container is a wrapper for Config
+type Container struct {
+	config atomic.Value
+}
+
+func NewContainer() *Container {
+	c := &Container{}
+	c.config.Store(defaultConfig)
+	return c
+}
+
+// NotifyPolicyChange to receive policy when it changes
+func (c *Container) NotifyPolicyChange(cfg *Config) {
+	c.config.Store(cfg)
+}
+
+func (c *Container) GetAclRule() acl.RejectFunc {
+	return func(ctx context.Context, request interface{}) (reason error) {
+		cfg := c.config.Load().(*Config)
+		if !cfg.Enable {
+			return nil
+		}
+		if fastrand.Intn(100) < cfg.Percentage {
+			return errRejected
+		}
+		return nil
+	}
+}

pkg/degradation/item_degradation_test.go

@@ -0,0 +1,40 @@
+// Copyright 2024 CloudWeGo Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package degradation
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/cloudwego/kitex/pkg/acl"
+	"github.com/cloudwego/thriftgo/pkg/test"
+)
+
+var errFake = errors.New("fake error")
+
+func invoke(ctx context.Context, request, response interface{}) error {
+	return errFake
+}
+
+func TestNewContainer(t *testing.T) {
+	container := NewContainer()
+	aclMiddleware := acl.NewACLMiddleware([]acl.RejectFunc{container.GetAclRule()})
+	test.Assert(t, errors.Is(aclMiddleware(invoke)(context.Background(), nil, nil), errFake))
+	container.NotifyPolicyChange(&Config{Enable: false, Percentage: 100})
+	test.Assert(t, errors.Is(aclMiddleware(invoke)(context.Background(), nil, nil), errFake))
+	container.NotifyPolicyChange(&Config{Enable: true, Percentage: 100})
+	test.Assert(t, errors.Is(aclMiddleware(invoke)(context.Background(), nil, nil), errRejected))
+}

server/suite.go

@@ -43,7 +43,7 @@ func NewSuite(service string, cli zookeeper.Client, opts ...utils.Option) *Zooke
 	return su
 }
 
-// Options return a list client.Option
+// Options return a list server.Option
 func (s *ZookeeperServerSuite) Options() []server.Option {
 	opts := make([]server.Option, 0, 2)
 	opts = append(opts, WithLimiter(s.service, s.zookeeperClient, s.opts))