How to configure Juju spaces¶

Caution

Juju spaces are only available on VM charms.

Use Juju spaces to select separate networks for MongoDB traffic and client connections. This guide configures spaces at deployment time for Charmed MongoDB on machines (VM), using a local LXD deployment.

The example uses these endpoint bindings:

Endpoint	Space	Subnet	Traffic
`database-peers`	`peers`	`10.137.180.0/24`	Communication between replica-set members
`database`	`clients`	`10.137.181.0/24`	Client connections to MongoDB

Prerequisites¶

An initialized LXD installation and permission to manage its networks with sudo lxc.
A bootstrapped Juju controller on LXD and a model selected for this deployment. See How to deploy via the Juju CLI.
The two example subnets must not overlap with existing networks on your host.

Create the LXD networks¶

Create one bridge for replica-set members and another for clients:

sudo lxc network create peers --type=bridge \
  ipv4.address="10.137.180.1/24" ipv4.nat=True \
  ipv6.address=none dns.mode=none
sudo lxc network create clients --type=bridge \
  ipv4.address="10.137.181.1/24" ipv4.nat=True \
  ipv6.address=none dns.mode=none

Prevent these additional networks from advertising a default gateway or DNS server over DHCP, so machines continue to use their existing network for those services:

sudo lxc network set clients raw.dnsmasq "dhcp-option=3
dhcp-option=6"
sudo lxc network set peers raw.dnsmasq "dhcp-option=3
dhcp-option=6"

Register the spaces in Juju¶

Refresh Juju’s network information, then associate each subnet with a space:

juju reload-spaces
juju add-space clients 10.137.181.0/24
juju add-space peers 10.137.180.0/24
juju spaces

Check that clients contains 10.137.181.0/24 and peers contains 10.137.180.0/24.

Deploy MongoDB and the client¶

Deploy three MongoDB units with access to both spaces and bind the endpoints to their respective networks:

juju deploy mongodb --channel 8/stable \
  --constraints spaces=peers,clients \
  --bind "alpha database-peers=peers database=clients" \
  -n 3

The spaces constraint requests access to the named networks. The endpoint bindings select the space for each relation endpoint. The standalone alpha sets the default binding for endpoints not explicitly listed.

Deploy the data-integrator charm with its mongodb endpoint bound to the clients space:

juju deploy data-integrator --config database-name=example \
  --constraints spaces=clients \
  --bind "alpha mongodb=clients"
juju integrate mongodb:database data-integrator:mongodb

Verify the client addresses¶

Wait for the applications to become active and idle:

juju status --watch 1s

Retrieve the client credentials:

juju run data-integrator/0 get-credentials

Inspect the connection URI in the action output (the uris field). Every MongoDB host address in that URI should belong to 10.137.181.0/24, the clients subnet, rather than the peers subnet.

Deploy on public clouds¶

For a public-cloud deployment, use the cloud’s networking configuration to provision the subnets and connectivity, then map those subnets to Juju spaces and bind the application endpoints. The LXD bridge commands above apply only to the local example.

See the Charmed MongoDB reference architectures for public-cloud deployment references, and Juju’s guide to managing spaces for space configuration.