Dubbo: support consul as registry center, config center and metadata center

[xiakun1201]

ZK cluster is too heavy，i strongly recommend consul after trying it，i think dubbo should support consul.

[chickenlj]

@MrXiaKun We recommend use english, so everyone can get involved.
We can discuss here

[chickenlj]

What do you exactly mean by too heavy?
As far as i know, these two solutions both based on strong consistency protocol. Consul made a specifically abstraction for Service Discovery(which means we can do less work when using consul as Service Registry), but do these changes makes any performance difference?

[kirbylynx]

I guess consul has higher availability performance than zookeeper.
And, as a java-based application, zookeeper uses much more memory on each server if deployed as cluster. Consul need less memory to run. I guess this is what @MrXiaKun means by too heavy.

[takeseem]

我认为他的意思是用zk来开发太难了。

• zk实际本身对资源的消耗是非常少的，无论是客户端还是服务器

I gues zookeeper too heavy, he meant to use zookeeper to develop too hard.

• zk actual consumption of resources is very small, whether it is client or server

[mthhk]

这个is为什么关闭了呢？
对于一些有consul，但是无zk的场景，想用dubbo就有些难受。

[byronzoz]

建议把consul支持起来

[xiangkaiy]

Does dubbo support consul now?

[ettingshausen]

Does dubbo support consul now?

@xiangkaiy
https://github.com/apache/dubbo-samples/tree/master/java/dubbo-samples-consul