Implement the juju-run symlink in jujud

Implement the juju-run symlink in jujud

Adds a command in the jujud executable so if the executable is called as
juju-run, it will attempt to connect to the rpc server being run by the unit
specified as the first arg.

In order to get the return code passed out of the command infrastructure I
added a new error type in the cmd package called "rcPassthroughError", which
has a return code in it.

We use the jujud from the machine agent as the target of the juju-run symlink
as we can add the symlink using cloud-init and we know there is only one
machine agent.

https://code.launchpad.net/~thumper/juju-core/jujuc-run/+merge/198865

Requires: https://code.launchpad.net/~thumper/juju-core/uniter-run-commands/+merge/198830

(do not edit description out of merge proposal)

[thumper, 2013-12-13 03:57:30]

Please take a look.

[wallyworld, 2013-12-13 04:17:33]

LGTM with some tweaks and a suggestion

https://codereview.appspot.com/41660044/diff/1/cmd/cmd.go
File cmd/cmd.go (right):

https://codereview.appspot.com/41660044/diff/1/cmd/cmd.go#newcode20
cmd/cmd.go:20: type rcPassthroughError struct {
Why not use a type alias?

https://codereview.appspot.com/41660044/diff/1/cmd/cmd.go#newcode33
cmd/cmd.go:33: func NewRcPassthroughError(code int) error {
Need doc here and/or the struct definition to say what it is for

https://codereview.appspot.com/41660044/diff/1/cmd/jujud/main.go
File cmd/jujud/main.go (right):

https://codereview.appspot.com/41660044/diff/1/cmd/jujud/main.go#newcode118
cmd/jujud/main.go:118: code = cmd.Main(&RunCommand{}, cmd.DefaultContext(),
args[1:])
Should we follow the pattern used for jujuc and jujud and have a jujurunMain
method?

https://codereview.appspot.com/41660044/diff/1/cmd/jujud/run.go
File cmd/jujud/run.go (right):

https://codereview.appspot.com/41660044/diff/1/cmd/jujud/run.go#newcode67
cmd/jujud/run.go:67: c.unit = names.UnitTag(c.unit)
can we have a comment here explaining what is being done ie unit can be either a
name or tag?

https://codereview.appspot.com/41660044/diff/1/environs/cloudinit/cloudinit.go
File environs/cloudinit/cloudinit.go (right):

https://codereview.appspot.com/41660044/diff/1/environs/cloudinit/cloudinit.g...
environs/cloudinit/cloudinit.go:242: fmt.Sprintf("ln -s %s/tools/%s/jujud
/usr/local/bin/juju-run", cfg.DataDir, machineTag),
please use cfg.jujuTools()

[thumper, 2013-12-13 04:54:31]

Please take a look.

https://codereview.appspot.com/41660044/diff/1/cmd/cmd.go
File cmd/cmd.go (right):

https://codereview.appspot.com/41660044/diff/1/cmd/cmd.go#newcode20
cmd/cmd.go:20: type rcPassthroughError struct {
On 2013/12/13 04:17:33, wallyworld wrote:
> Why not use a type alias?

I think because I want a real struct here. A type alias to int is just weird.

https://codereview.appspot.com/41660044/diff/1/cmd/cmd.go#newcode33
cmd/cmd.go:33: func NewRcPassthroughError(code int) error {
On 2013/12/13 04:17:33, wallyworld wrote:
> Need doc here and/or the struct definition to say what it is for

Done.

https://codereview.appspot.com/41660044/diff/1/cmd/jujud/main.go
File cmd/jujud/main.go (right):

https://codereview.appspot.com/41660044/diff/1/cmd/jujud/main.go#newcode118
cmd/jujud/main.go:118: code = cmd.Main(&RunCommand{}, cmd.DefaultContext(),
args[1:])
On 2013/12/13 04:17:33, wallyworld wrote:
> Should we follow the pattern used for jujuc and jujud and have a jujurunMain
> method?

We could, but it would just be one line... so I chose not to.

https://codereview.appspot.com/41660044/diff/1/cmd/jujud/run.go
File cmd/jujud/run.go (right):

https://codereview.appspot.com/41660044/diff/1/cmd/jujud/run.go#newcode67
cmd/jujud/run.go:67: c.unit = names.UnitTag(c.unit)
On 2013/12/13 04:17:33, wallyworld wrote:
> can we have a comment here explaining what is being done ie unit can be either
a
> name or tag?

Done.

https://codereview.appspot.com/41660044/diff/1/environs/cloudinit/cloudinit.go
File environs/cloudinit/cloudinit.go (right):

https://codereview.appspot.com/41660044/diff/1/environs/cloudinit/cloudinit.g...
environs/cloudinit/cloudinit.go:242: fmt.Sprintf("ln -s %s/tools/%s/jujud
/usr/local/bin/juju-run", cfg.DataDir, machineTag),
On 2013/12/13 04:17:33, wallyworld wrote:
> please use cfg.jujuTools()

No, but comment added to explain why.