Add skip_network_error_at_init option to forward output. fix #731

[repeatedly]

This option is available when heartbeat_type is tcp for now.

[repeatedly]

Do we need to support udp heartbeat?

[harmw]

I would say this feature should be protocol-agnostic, thus yes UDP should be supported, though you could just merge it now with a disclaimer of some sorts and only support TCP 😄

To my understanding, the heartbeat is used to ping/check a backend or forwarder, whereas this PR is about mere DNS resolving.

[mgcrea]

👍 this is really needed!

[tagomoris]

I think UDP should be supported too.
Any progress?

[repeatedly]

We can support UDP but it makes code complicated, e.g. lazy initialization for socket and Heartbeater.
It needs re-writing socket handling of out_forward.
So I want to delay UDP support after other important changes are merged.

[tagomoris]

I will come back to this issue after implementing forward plugins with socket/server plugin helpers and v0.14 APIs.

[tagomoris]

I created #1399 based on v0.14 code base.