Connecting Gaia Sky instances

Gaia Sky offers a method to connect different instances together so that their internal state is synchronized. The model uses a master-slave scenario, where one (and only one) instance acts as a master and one or more instances act as slaves, getting their internal states updated over a network. The user interacts with the master and all slaves are updated accordingly.

This section describes only how to configure the master and the slave instances in order to connect them together. This method is used to provide multi-projector rendering support (i.e. planetarium domes), but extra steps are needed in order to configure the orientation, distortion warp and blend settings for each slave instance.

Hint

Multi-projector configuration is covered in the “Planetarium mode multi-projector setup” section.

Configuration

The configuration is easy and painless. You will need to launch each instance of Gaia Sky using a different configuration file (global.properties). You can run Gaia Sky with a specific configuration file by using the -p or --properties command line flags:

$  gaiasky -p ~/.config/gaiasky/global.master.properties

The next sections explain how to configure the master and the slaves.

Configuration: slave instance(s)

You can have as many slave instances as you want, but here we’ll explain the process of setting up two slaves.

Copy the current global.properties file in your config folder (see folders) into global.slave0.properties. The name is irrelevant, but choose something meaningful. Repeat with global.slave1.properties.
Set the property program.net.slave=true in each file and make sure that program.net.master is set to false.
Set the desired port to listen to in program.restport. For example, to use the port 13900 just set the property program.restport=13900. Use a different port for each slave (i.e. slave 0 listens to 13900, slave 1 listens to 13901, etc.).

For exmaple, to set up a slave in port 13900, make sure that the following lines are in its configuration file:

program.net.master=false
program.net.slave=true
program.restport=13900

The slave instances should be launched before the master. Launch the slave(s) with:

$  # Launch slave 0
$  gaiasky -p /path/to/global.slave0.properties
$  # Launch slave 1
$  gaiasky -p /path/to/global.slave1.properties

Once the slave(s) have been launched, you can verify that the API is working by visiting http://localhost:13900/api/help with your browser. Modify the port with whatever port you are using.

Hint

Only the master is starting the scripting server. The slaves are automatically forbidden to do so!

Configuration: master instance

Copy the current global.properties file into global.master.properties and edit the following lines.

Set the property program.net.master=true and make sure that program.net.slave is set to false.
Add the locations of all desired slaves under the properties program.net.master.slaves.n=URL, where n is an integer that goes from 0 to the number of slaves - 1.

For example, in order to connect the master with two slaves, both running locally (localhost) on ports 13900 and 13901, add the following to the global.master.properties file:

program.net.master=true
program.net.slave=false
program.net.master.slave.0=http://localhost\:13900/api/
program.net.master.slave.1=http://localhost\:13901/api/

Then, just launch the master (after the slaves are running!):

$  gaiasky -p /path/to/global.master.properties

Caveats

Even though this offers a very flexible system to connect several instances of Gaia Sky together, each instance is a fully-fledged application with its own copy of the scene graph and the data structures. This means that, if you run them locally, the data and scene graph will be replicated several times in memory, possibly consuming lots of gigabytes.

Handle it with care.