Prevote connection timeout

[kishorenc]

While prevote RPC uses a timeout of election_timeout_ms here, the connection timeout of the channel itself is not set, so Channel is using the default of 200 ms.

This leads to the following errors on a cross region set-up where latency between nodes can be high:

W20200916 15:18:12.090553 31353 node.cpp:1464] node default_group:10.14.67.152:8107:443 request PreVote from 10.18.62.245:8107:443 error: [E110]Fail to connect Socket{id=257698038587 addr=10.18.62.245:8107:8107} (0x0x7f487f59fc80): Connection timed out

The same is an issue in other places where RPC is used as well, including in replicator.cpp where the channel connection timeout is commented out.

Is there a rational for not setting the connection time out along with request timeout?

[PFZheng]

This leads to the following errors on a cross region set-up where latency between nodes can be high:

The reason why the connect timeout is not set is that, we think the default value in brpc is fine.
If you need to set the connect timeout value, you can push a patch. I think it's ok to add such options.