Add typed error on connection failure

[abronan]

Add typed error on connection failure. This is convenient to differentiate between legitimate container operation failures and a connection failure to mark a Swarm node as Healthy or Unhealthy.

/cc @vieux @dongluochen

Signed-off-by: Alexandre Beslic abronan@docker.com

[dongluochen]

LGTM.

[vieux]

The if is different now. It's a change of behaviour, not sur we want that.

• With a connection error and no TLS -> no more "Are you trying to connect to a TLS-enabled daemon without TLS"
• With an error different than connection error and no TLS -> "Are you trying to connect to a TLS-enabled daemon without TLS"

[abronan]

Good point, this breaks the error flow for the TLS error. Let me change that.

[abronan]

@vieux PTAL

[vieux]

@abronan so you will the the new error only when you use TLS, is it ok ?

[abronan]

@vieux I think this way we don't break the current behavior (which is also disputable as we throw a TLS related message on something that might be completely unrelated, ie. remote endpoint unprotected but we throw the TLS message anyway because it is not a connection issue).

I added the test right after this one to not break existing clients and change the behavior, but ultimately we should only check for a connection issue here and not try to guess a TLS related error (I mimic fsouza/dockerclient by doing this 😄).

I might be missing something though, is there a better alternative?

[vieux]

I don't see anything better, I'm just not sure this will be helpful

[vieux]

LGTM