Document environment-specific placement directives

[axw]

There's now support (on trunk) for juju bootstrap/add-machine to take an optional environment-specific placement directive. MAAS is the only provider that currently supports such directives; we use this to bootstrap/add machines based on specific nodes in MAAS.

e.g.
juju bootstrap
juju add-machine

[axw]

We now also have support in the ec2 provider for availability zone placement. The syntax for this placement directive is zone=<zonename>, e.g. zone=us-east-1b.

This will also be in the openstack provider very soon.

[marcoceppi]

Per juju/juju#37, this appears to be available for OpenStack too

[axw]

Indeed it is. Exactly the same format for openstack as in ec2. Note that not all OpenStack instances are equal, and not all support availability zones. HP Cloud's US West region has a few AZs (az1, az2, az3).

[pmatulis]

@evilnick and others

we have some of this in charms-ha and in commands but there is nothing specific regarding what providers support this and no caveats (a provider may or may not support it depending on implementation).

is augmenting the above two documents good enough or should we:

• start building out provider-specific docs (beyond installation)?
• include this in a provider's install/config page? (my preference)

[pmatulis]

• Consensus in issue Add zone placement directive to provider documentation #187 is to put this stuff in provider's install/config page.
• Still need to augment charms-ha and commands

[pmatulis]

Submitted PR #596

[pmatulis]

PR merged. Closing.