Is your feature request related to a problem? Please describe.
Apollo use eureka as registry now, it need eureka's configuration like url when deployment as cluster mode.

Why?
Sometime config service or admin service will startup failed due to the configuration themself, and the eureka's configuration maybe a little hard to config when run on multiple idc(a network connected region).

Describe the solution you'd like
register:
when config service and admin service's instance startup, they register to self's database table, and send heartbeat on runtime.

discovery:
origin data select from database table, and cache them by jvm memory.

Use metadata(mutiple key values) or a label in local .properties file to support only discover same idc's instance.

Additional context
benefit:
Auto scale config service and admin service without config registry's url, because they use same database, their url will save in a same table for service discovery.

cost:

• need to maintain a new database table.
• a clearup policy to clean this database table.
• health check