why use ip for nameserver

[lishitiancn]

We can see that there are 1 name service Pods running on 1 nodes and their IP addresses. Modify the nameServers field in the rocketmq_v1alpha1_broker_cr.yaml file using the IP addresses.

[liuruiyiyang]

Because the brokers need to know the IP addresses of the node where the namesrv(NameServer) services are deployed on, so that the brokers could communicate with the namesrv services clusters.

However, this configuration step is for the first time when initialize the broker cluster. When up-scale the namesrv cluster, the new IP list of the namesrv cluster is automatically maintained and told to the broker cluster.

[Kaijun]

Because the brokers need to know the IP addresses of the node where the namesrv(NameServer) services are deployed on, so that the brokers could communicate with the namesrv services clusters.

However, this configuration step is for the first time when initialize the broker cluster. When up-scale the namesrv cluster, the new IP list of the namesrv cluster is automatically maintained and told to the broker cluster.

why not using kubernetes service dns instead of static IP?

[Kaijun]

I have to create nameserver in the first place, and extract the ip which nameserver is using, then finally i could fill it into broker cr.

the order of deploying makes it not possible to deploy a complete rocketmq service the way by using a simple stack. it's also kind of against the philosophy of kubernetes which emphasizes state oriented.

@liuruiyiyang @vongosling

[duhenglucky]

@Kaijun use the DNS will be a better choice, so would you like to submit a PR to polish it?

[hzliangbin]

@duhenglucky According to the blog of AliMiddleware, the nameserver cluster is decentralization. And each broker will connect to all nameservers to refresh broker's info. It's OK when NameServer' size is 1. kubernetes service will always lead to one backend pod.

But when there are 2 or more nameservers, the kubernetes service will forward to only one of the backend pods based on some loadbanlance strategy.

A not that perfect solution :
Use headless service. The brokers use Podname.Servicename.Namespacename instead IP to register to namerservers. However the impact on performance should be considered.

[vongosling]

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