Package install runs parallel

[elcuervo]

Since we have bash on our side we can speed up the package installation.

And yes... it's because of this rubygems/bundler#2481

[pote]

This is the best pull request ever, you're awesome <3

[gravis]

What if some packages have the same dependencies?
Don't you expect some issues there (2 go processes could write the same files at the same moment, even if probability is low)?
What do you think?

[elcuervo]

@gravis you mean two johnny-deps running at the same time?

[gravis]

I mean 2 go get -v -u -d, since they're running in parallel now.
The blocking I see would be:

A => B => C
D => B

If A and D gets installed at the same time, there's a tiny chance to install B concurrently (which could lead to broken files). I know, it's really unlikely, but still. Maybe a simple note in the README about that troubleshooting (in which case, the packages should be reinstalled from scratch)?
My 2c ;)

[elcuervo]

Since go get uses git under the hood I don't really think that it will lead to broken files: http://code.google.com/p/go/source/browse/src/cmd/go/vcs.go#94
Even if it's a fresh clone I don't see this scenario happening. But I'll try to force it and see how it goes.

[gravis]

yes, the best test I see is to run 2 git command at the same time, cloning the same repo, and see how it goes.
I would bet on a successful result :)
Probably git is putting a lock file inside the folder, but then the second go get will probably fail, and won't install the remaining packages ;)
Sorry, I really like your approach, and don't want to criticize anything, I just had bad experiences like that in the past :)

[elcuervo]

Criticism is the smartest way of communication if you do it right. Your comments are prefect on that way so keep them coming!. We all want this tool to get better and better.
Two pull at the same moment will make one of them fail but that won't affect the consistency of the files but it'll make johnny-deps crash.
I agree with adding some sort of troubleshooting part in the README.

Thank you for seeing it!
👉

[gravis]

Welcome! 👍

[pote]

Great call @gravis , I hadn't thought of this but it certainly merits some documentation and possibly a test.

Dependency resolution inside johnny-deps is something Im thinking about, I'll keep this in mind and think of a way to avoid the edge case.

[elcuervo]

Hey @gravis && @pote: what do you think? https://github.com/elcuervo/johnny-deps/commit/f24a436379abcf54540b9ccb6e00136d7967ed3d