Docker Machine v0.5.1 breaks compatibility with v0.5.0 drivers

[janeczku]

This particularly affects use of drivers not distributed with the machine binary.

For simplicity this is demonstrated with the virtualbox driver.

Steps to reproduce

1. $ git clone https://github.com/docker/machine.git
2. $ cd machine && git checkout v0.5.0
3. $ go build -a -o /usr/local/bin/docker-machine-driver-virtualbox cmd/machine-driver-virtualbox.go
4. $ git checkout v0.5.1
5. $ go build -a -o /usr/local/bin/docker-machine cmd/machine.go
6. $ docker-machine create -d virtualbox

Expected result

Machine continuous to work

Actual result

Error occurs and Machine exits

WARNING >>> Error attempting heartbeat call to plugin server: rpc: can't find service RPCServerDriver.Heartbeat
Error attempting to invoke binary for plugin 'virtualbox': rpc: can't find service RPCServerDriver.GetVersion

This is probably caused by commit 89d9854 which changed the RPC API interface breaking compatibility with all drivers compiled against v0.5.0 or earlier.

Reference PR #2321
/cc @nathanleclaire @dmp42

[nathanleclaire]

Ah, of course, the linting changes. Thanks for the report @janeczku.

I'm pretty upset about this (and I really am profusely sorry) as it wasn't intended to break compatibility but I think the linting changes are over (new PRs are being run through golint) and there is nothing we can do about it now unfortunately. In the future we will be more disciplined about not breaking the API.

[dgageot]

Yes, that's bad. We had to do it. We should have done it before 0.5.0 and didn't have time.

[legal90]

That's really sad that backward & forward incompatible stuff was done in the scope of patch level release. May be, it is reasonable to bump a minor version at least? (0.6.0)

[allingeek]

You can still fix this AND keep the linting change. There is no reason to tie the API service and method names to Go types. Please consider reopening, making the change, and restoring the API.

Should I send a PR?

[nathanleclaire]

@allingeek Interesting, I had not considered that as an alternative. Would love to see such a PR.

[allingeek]

I've verified that a docker-machine binary with this patch will work with both plugin generations.

[janeczku]

@allingeek you rock! 👏 📣

[allingeek]

Can this be closed after the patch?

[nathanleclaire]

Yes I think so!