Add "pgp-happy-eyeballs" in Travis to help cut down on gpg-related issues

[tianon]

Refs docker-library/php#666

[rbreslow]

I feel nervous about the amount of messing around pgp-happy-eyeballs does with Docker internals.

In our experience across all the Docker official images, the ipv4 pool isn't any more reliable on the whole than the ha pool (and in fact is made up of a number of the same servers). I think you probably just happened to hit a different server via ipv4 than you did via ha.

This hasn't been my experience so far. We haven't had a single failure in our builds. Why would the IPv4 pool contain the same IPv6 servers from the ha pool?

[yosifkit]

messing around pgp-happy-eyeballs does with Docker internals

That's just adding a DNS server so that things in a docker build use that to look up pgp servers and get the caching proxy instead of the real server.

Why would the IPv4 pool contain the same IPv6 servers from the ha pool?

Because any of the IPv6 servers are also IPv4 servers: https://sks-keyservers.net/status/. I don't see any indication that they are IPv6 only. And ha, currently, contains one server that supports IPv6 and one that does not.

We haven't had a single failure in our builds.

Lucky you 😄 We see it all too often. Like this one which is not the IPv6 Cannot assign requested address error (quoted below for when the travis build log goes away).

+ gpg --keyserver ha.pool.sks-keyservers.net --recv-keys B97B0AFCAA1A47F044F244A07FCC7D46ACCC4CF8
gpg: keybox '/tmp/tmp.FxfD4RbclK/pubring.kbx' created
gpg: keyserver receive failed: No data

[rbreslow]

Thank you for adding more clarity @yosifkit!