动态配置规则 (ConfigurationRule) 是 Dubbo 设计的在无需重启应用的情况下，动态调整 RPC 调用行为的一种能力，也称为动态覆盖规则，因为它是通过在运行态覆盖 Dubbo 实例或者 Dubbo 实例中 URL 地址的各种参数值，实现改变 RPC 调用行为的能力。
使用动态配置规则，有以下几条关键信息值得注意：
以下一个应用级别的配置示例，配置生效后，shop-detail 应用下提供的所有服务都将启用 accesslog，对 shop-detail 部署的所有实例生效。
configVersion: v3.0
scope: application
key: shop-detail
configs:
- side: provider
parameters:
accesslog: 'true'
以下是一个服务级别的配置示例，key: org.apache.dubbo.samples.UserService 和 side: consumer 说明这条配置对所有正在消费 UserService 的 Dubbo 实例生效，在调用失败后都执行 4 次重试。match 条件进一步限制了消费端的范围，限定为只对应用名为 shop-frontend 的这个消费端应用生效。
configVersion: v3.0
scope: service
key: org.apache.dubbo.samples.UserService
configs:
- match:
application:
oneof:
- exact: shop-frontend
side: consumer
parameters:
retries: '4'
配置规则主体，定义要设置的目标服务或应用、具体的规则配置。具体配置规则 (configs) 可以设置多条。
| Field | Type | Description | Required |
|---|---|---|---|
| configVersion | string | The version of the configuration rule definition, currently available version is v3.0 | Yes |
| scope | string | Supports service and application scope configurations. | Yes |
| key | string | The identifier of the target service or application that this rule is about to apply to. - If scope:serviceis set, then keyshould be specified as the Dubbo service key that this rule targets to control.- If scope:application is set, then keyshould be specified as the name of the application that this rule targets to control. | Yes |
| enabled | bool | Whether enable this rule or not, set enabled:false to disable this rule. | Yes |
| configs | Config[] | The match condition and configuration of this rule. | Yes |
具体的规则配置定义，包含生效端 (consumer 或 provider) 和过滤条件。
| Field | Type | Description | Required |
|---|---|---|---|
| side | string | Especially useful when scope:serviceis set.- side: providermeans this Config will only take effect on the provider instances of the service key.- side:consumermeans this Config will only take effect on the consumer instances of the service key | Yes |
| parameters | map<string, string> | The keys and values this rule aims to change. | Yes |
| match | MatchCondition | A set of criterion to be met in order for the rule/config to be applied to the Dubbo instance. | No |
| enabled | bool | Whether enable this Config or not, will use the value in ConfigurationRule if not set | No |
过滤条件，用来设置规则对哪个服务 (service)、应用 (application)、实例 (address)，或者包含哪些参数 (param) 的实例生效。
| Field | Type | Description | Required |
|---|---|---|---|
| address | StringMatch | The instance address matching condition for this config rule to take effect. - xact: “value” for exact string match - prefix: “value” for prefix-based match - regex: “value” for RE2 style regex-based match (https://github.com/google/re2/wiki/Syntax)). | No |
| service | StringMatch (oneof) | The service matching condition for this config rule to take effect. Effective when scope: application is set.- exact: “value” for exact string match - prefix: “value” for prefix-based match - regex: “value” for RE2 style regex-based match (https://github.com/google/re2/wiki/Syntax)). | No |
| application | StringMatch (oneof) | The application matching condition for this config rule to take effect. Effective when scope: service is set.- exact: “value” for exact string match - prefix: “value” for prefix-based match - regex: “value” for RE2 style regex-based match (https://github.com/google/re2/wiki/Syntax)). | No |
| param | ParamCondition[] | The Dubbo url keys and values matching condition for this config rule to take effect. | No |
定义实例参数 (param) 过滤条件，对应到 Dubbo URL 地址参数。
| Field | Type | Description | Required |
|---|---|---|---|
| key | string | The name of the key in the Dubbo url address. | Yes |
| value | StringMatch (oneof) | The matching condition for the value in the Dubbo url address. | Yes |
| Field | Type | Description | Required |
|---|---|---|---|
| exact | string (oneof) | exact string match | No |
| prefix | string (oneof) | prefix-based match | No |
| regex | string (oneof) | RE2 style regex-based match (https://github.com/google/re2/wiki/Syntax)). | No |