Add EHOSTUNREACH to retry conditions

[matthee]

Adds the Errno::EHOSTUNREACH to the retry conditions when trying to connect to a host endpoint. I'm not sure, under which conditions this specific errno is thrown, however I've experienced it when playing around with the async-dns wikipedia example.

Fixes #18.

Types of Changes

• Bug fix.

Contribution

• I tested my changes locally.
• I agree to the Developer's Certificate of Origin 1.1.

[jaredcwhite]

@matthee FYI, when I tried this out it said it needed to be Errno:EHOSTUNREACH (the E at the start of the const).

[matthee]

Well, this is embarrassing 😅
@jaredcwhite You are absolutely right! Fixed it - thanks for catching this bug!

I ran the tests locally and everything seemed to be fine. I discovered that the connect method is covererd by the test suite. However, there seem to be no tests for the retry logic. @ioquatix I'm not sure on how to best implement these - could you give me a hint?

[ioquatix]

You could provide a custom wrapper and write:

expect(wrapper).to receive(:connect).and_raise(Errno::EHOSTUNREACH)

https://github.com/socketry/sus/blob/08a13e433dc4f234b3dc65e0a25c770516634070/context/mocking.md?plain=1#L48-L56

Hope that helps.

[matthee]

I completely forgot about this PR - i will have a go during the upcoming holiday season.