testing: let the OS choose a port to listen on.

testing: let the OS choose a port to listen on.

This stops random clashes between tests running concurrently
or when the server hasn't finished soon enough after it's destroyed.

Also make testing panic on error rather than use Fatalfer.

https://code.launchpad.net/~rogpeppe/juju/go-zk-testing-random-port/+merge/99314

(do not edit description out of merge proposal)

[rog, 2012-03-26 12:51:37]

Please take a look.

[niemeyer, 2012-03-26 19:59:05]

If the port selection is simplified in one of the two ways suggested, LGTM.

https://codereview.appspot.com/5909062/diff/8/testing/zk.go
File testing/zk.go (right):

https://codereview.appspot.com/5909062/diff/8/testing/zk.go#newcode31
testing/zk.go:31: p := <-randomPorts
This may be simpler with:

    p := rand.Intn(65536-1025) + 1025

But, I think this may be even simpler if you use :0 as the port in the Listen
below, and allow the OS to chose the port for you. Then, pick the address out of
the listener before closing it.

[rog, 2012-03-26 20:23:08]

https://codereview.appspot.com/5909062/diff/8/testing/zk.go
File testing/zk.go (right):

https://codereview.appspot.com/5909062/diff/8/testing/zk.go#newcode31
testing/zk.go:31: p := <-randomPorts
On 2012/03/26 19:59:05, niemeyer wrote:
> This may be simpler with:
> 
>     p := rand.Intn(65536-1025) + 1025
> 
> But, I think this may be even simpler if you use :0 as the port in the Listen
> below, and allow the OS to chose the port for you. Then, pick the address out
of
> the listener before closing it.

it's true the former is probably better - i was thinking that i wanted the rng
to be seeded randomly (and didn't want to interact badly with others doing the
same thing) but it perhaps doesn't matter too much.

allowing the os to choose the port for me seems like it's inviting a race with
another program doing the same thing, but if you think that's ok, i'll go with
it.

[niemeyer, 2012-03-26 21:19:18]

https://codereview.appspot.com/5909062/diff/8/testing/zk.go
File testing/zk.go (right):

https://codereview.appspot.com/5909062/diff/8/testing/zk.go#newcode31
testing/zk.go:31: p := <-randomPorts
On 2012/03/26 20:23:08, rog wrote:
> allowing the os to choose the port for me seems like it's inviting a race with
> another program doing the same thing, but if you think that's ok, i'll go with
> it.

Yeah, I think it's fine, and actually less likely to yield issues. If the OS
picks the same port when two programs request a random port in quick succession,
that'd be a really bad implementation.

[rog, 2012-03-27 14:06:44]

*** Submitted:

testing: let the OS choose a port to listen on.

This stops random clashes between tests running concurrently
or when the server hasn't finished soon enough after it's destroyed.

Also make testing panic on error rather than use Fatalfer.

R=niemeyer
CC=
https://codereview.appspot.com/5909062