# Overview 

This principle charm provides the OpenStack Neutron API service which was previously provided by the nova-cloud-controller charm.

When this charm is related to the nova-cloud-controller charm the nova-cloud controller charm will shutdown its api service, de-register it from keystone and inform the compute nodes of the new neutron url.

# Usage

To deploy (partial deployment only):

    juju deploy neutron-api
    juju deploy neutron-openvswitch

    juju add-relation neutron-api mysql
    juju add-relation neutron-api rabbitmq-server
    juju add-relation neutron-api neutron-openvswitch
    juju add-relation neutron-api nova-cloud-controller

This charm also supports scale out and high availability using the hacluster charm:

    juju deploy hacluster neutron-hacluster
    juju add-unit neutron-api
    juju set neutron-api vip=<VIP FOR ACCESS>
    juju add-relation neutron-hacluster neutron-api

## HA/Clustering

There are two mutually exclusive high availability options: using virtual
IP(s) or DNS. In both cases, a relationship to hacluster is required which
provides the corosync back end HA functionality.

To use virtual IP(s) the clustered nodes must be on the same subnet such that
the VIP is a valid IP on the subnet for one of the node's interfaces and each
node has an interface in said subnet. The VIP becomes a highly-available API
endpoint.

At a minimum, the config option 'vip' must be set in order to use virtual IP
HA. If multiple networks are being used, a VIP should be provided for each
network, separated by spaces. Optionally, vip_iface or vip_cidr may be
specified.

To use DNS high availability there are several prerequisites. However, DNS HA
does not require the clustered nodes to be on the same subnet.
Currently the DNS HA feature is only available for MAAS 2.0 or greater
environments. MAAS 2.0 requires Juju 2.0 or greater. The clustered nodes must
have static or "reserved" IP addresses registered in MAAS. The DNS hostname(s)
must be pre-registered in MAAS before use with DNS HA.

At a minimum, the config option 'dns-ha' must be set to true and at least one
of 'os-public-hostname', 'os-internal-hostname' or 'os-internal-hostname' must
be set in order to use DNS HA. One or more of the above hostnames may be set.

The charm will throw an exception in the following circumstances:
If neither 'vip' nor 'dns-ha' is set and the charm is related to hacluster
If both 'vip' and 'dns-ha' are set as they are mutually exclusive
If 'dns-ha' is set and none of the os-{admin,internal,public}-hostname(s) are
set

# Restrictions

This charm only support deployment with OpenStack Icehouse or better.

# Network Space support

This charm supports the use of Juju Network Spaces, allowing the charm to be bound to network space configurations managed directly by Juju.  This is only supported with Juju 2.0 and above.

API endpoints can be bound to distinct network spaces supporting the network separation of public, internal and admin endpoints.

Access to the underlying MySQL instance can also be bound to a specific space using the shared-db relation.

To use this feature, use the --bind option when deploying the charm:

    juju deploy neutron-api --bind "public=public-space internal=internal-space admin=admin-space shared-db=internal-space"

alternatively these can also be provided as part of a juju native bundle configuration:

    neutron-api:
      charm: cs:xenial/neutron-api
      num_units: 1
      bindings:
        public: public-space
        admin: admin-space
        internal: internal-space
        shared-db: internal-space

NOTE: Spaces must be configured in the underlying provider prior to attempting to use them.

NOTE: Existing deployments using os-*-network configuration options will continue to function; these options are preferred over any network space binding provided if set.