juju-core

juju-core
=========

juju is devops distilled.

Getting started
===============

`juju-core` is written in Go (http://golang.org), a modern, compiled, statically
typed, concurrent language. This document describes how to build `juju-core`
from source. If you are looking for binary releases of `juju-core`, they are
available from the Gophers PPA, `https://launchpad.net/~gophers/+archive/go`.

Installing Go
-------------

If you are using Precise or later, the `golang-go` package is available in the
main archive and can be installed with

    sudo apt-get install golang-go

Using Go compiled from source is also supported, but not covered in this document.

Setting GOPATH
--------------

When working with the source of Go programs, you should define a path within
your home directory (or other workspace) which will be your `GOPATH`. `GOPATH`
is similar to Java's `CLASSPATH` or Python's `~/.local`. `GOPATH` is documented
online at `http://golang.org/pkg/go/build/` and inside the `go` tool itself

    go help gopath

Various conventions exist for naming the location of your `GOPATH`, but it should
exist, and be writable by you. For example

    export GOPATH=${HOME}/work
    mkdir $GOPATH

will define and create `$HOME/work` as your local `GOPATH`. The `go` tool itself
will create three subdirectories inside your `GOPATH` when required; `src`, `pkg`
and `bin`, which hold the source of Go programs, compiled packages and compiled
binaries, respectively.

Setting `GOPATH` correctly is critical when developing Go programs. Set and
export it as part of your login script.

Add `$GOPATH/bin` to your `PATH`, so you can run the go programs you install:

    PATH="$PATH:$GOPATH/bin"

Other prerequisites
-------------------

A number of additional prerequisite packages are required to compile `juju-core`
and run the tests.  Running "make install-dependencies" from the source tree
will generally install these for you.

If you do choose to install them manually, here's what you need:

    sudo apt-get install build-essential bzr zip git-core mercurial \
        distro-info-data

Binaries for mongodb are also required, but a newer version than is present in
either 12.04 or 12.10 Ubuntu releases. Instead, you can get what you need from
the public bucket which juju uses when deploying itself:

    http://juju-dist.s3.amazonaws.com/tools/mongo-2.2.0-precise-amd64.tgz

Change the Ubuntu series name and architecture to match your system.

Note that the use of --upload-tools forces the instances to run with the same
series and architecture of your development system.  Currently the only
supported architecture that can be deployed is amd64, so you must develop on
64-bit machines.

Getting juju-core
=================

The easiest way to get the source for `juju-core` is to use the `go get` command.

    go get -v launchpad.net/juju-core/...

This command will checkout the source of `juju-core` and inspect it for any unmet
Go package dependencies, downloading those as well. `go get` will also build and
install `juju-core` and its dependencies. To checkout without installing, use the
`-d` flag. More details on the `go get` flags are available using

    go help get

At this point you will have the bzr working copy of the `juju-core` source at
`$GOPATH/launchpad.net/juju-core`. The source for any dependent packages will
also be available inside `$GOPATH`. You can use `bzr pull`, or the less convenient
`go get -u launchpad.net/juju-core/...` to update the source from time to time.
If you want to know more about contributing to `juju-core`, please read the
`CONTRIBUTING` companion to this file.

Building juju-core
==================

    go install -v launchpad.net/juju-core/...

Will build juju and install the binary commands into `$GOPATH/bin`. It is likely
if you have just completed the previous step to get the `juju-core` source, the
install process will produce no output, as the final executables are up-to-date.

Using juju-core
===============

After following the steps above you will have the `juju` client installed in
`GOPATH/bin/juju`. You should ensure that this version of `juju` appears earlier
in your path than any packaged versions of `juju-core`, or older Python juju
commands. You can verify this using

    which juju

--upload-tools
--------------

The `juju` client program, and the juju 'tools' are deployed in lockstep. When a
release of `juju-core` is made, the compiled tools matching that version of juju
are extracted and uploaded to a known location. This consumes a release version
number, and implies that no tools are available for the next, development, version
of juju. Therefore, when using the development version of juju you will need to
pass an additional flag, `--upload-tools` to instruct the `juju` client to build
a set of tools from source and upload them to the environment as part of the
bootstrap process.

    juju bootstrap -e your-environment --upload-tools {--debug}

Known issues
============

* If you have used the Python version of Juju, you cannot re-use the
  control-bucket on S3 for Go Juju.  Change the bucket name in your
  environments.yaml.

* juju-origin is not supported so it must be removed from the environment you
  define in environments.yaml if it exists.  At the moment --upload-tools is
  the work-around to use, though it does have the problems mentioned
  previously.