docker.local hostname in /etc/hosts not resolving on OSX for docker machine (causing rspec tests to fail)

I had a bug today where my rspec tests ran fine, down to the last expectation, but then I still got a “database connection timeout error”.

This is running rails locally, connecting to a postgres instance inside of docker, using docker machine.

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  • Docker machine instructions guided me to create an entry in my /etc/hosts file: docker.local 

    This worked fine for the test itself, but then something (probably some cleanup step after the test suite – possibly from DatabaseCleaner?) still raised an error about timing out connecting to the database.

    After a lot of investigation, debugging, even deleting and recreating the docker machine default container, I finally narrowed it down to if I replace docker.local with the actual IP address in the database config – it passes.

    So bottom line – some cleanup process didn’t have access to the /etc/hosts defined docker.local hostname.

    This is on OSX El Capitan.

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