Dynamic Routing Expansion

[kaori-seasons]

• [ ] I have searched the issues of this repository and believe that this is not a duplicate.
• [ ] I have searched the release notes of this repository and believe that this is not a duplicate.

Describe the feature

ConditionRouter only supports a few operators which cannot satisfy real usage in production. Now canary deployment is popular in micro services and Dubbo should have a native solution.

Users can specify the rules in config center such like following: when c.version==1.1 then s.version>=2.0 when c.version<1.1 then s.version<2.0 c is an embeded object which means client/consumer, s means server/provider As soon as the rules are deployed, it will be applied into the consumer side and changes the router. More complicated expressions, please refer to Apache Commons JEXL This expression language can be easily changed to Spring Expression Language(SpEL). But consider that dubbo is now and apache project, commons-jexl will be used as the default one.

[EarthChen]

This feature may be as an spi extension better.

[kaori-seasons]

This feature may be as an spi extension better.

Yes, there is a draft for this and I'm working on its current 3.2 api. After passing ci, I will submit a demo to dubbo-samples