Add option to run vtcombo and vttest local cluster with real topo server

[zhongr3n]

Signed-off-by: Zhong Ren zhong@zhongren.me

Description

Add option to run vtcombo and vttest local cluster with real topo server

• We want to share the topo server across multiple components for local functional tests. Because vtcombo starts its own process, there's no easy way to share the in-memory topo server across different components
• This change allow vtcombo to use an actual topo server endpoint
• Tested with local consul server

consul agent -dev

go run ~/stripe/vitess/go/cmd/vttestserver/main.go -remote_topo_implementation=consul -remote_topo_global_server_address=localhost:8500 -remote_topo_global_root=root

Related Issue(s)

N/A

Checklist

• Should this PR be backported?
• Tests were added or are not required
• Documentation was added or is not required

Deployment Notes

N/A

[mattlord]

Thank you for doing this! I can definitely see how this will be useful. I could put it to good use myself for some consul specific testing :-)

I had a few nits, but all very minor things. Do you think it's worth adding a unit test to be sure this doesn't break down the road?

[deepthi]

Looks good overall.
I might be reading this wrong, but I don't see any actual tests exercising the new options. We need at least one.

[zhongr3n]

Thanks for reviewing folks. Added a unit test using consul external topo, and addressed other feedback.

[5antelope]

if we use consul agent -dev i think we could do consul leave for a graceful shutdown and don't need to call os.Remove

[zhongr3n]

tried consul leave and it adds 10 seconds for grace shutdown. keeping process.kill

[zhongr3n]

looking into test failure

[5antelope]

LGTM

[deepthi]

Thank you for the contribution!