Clustering

Pulsar is able to run on a cluster, thereby letting actors and channels communicate across machines. The Pulsar/Quasar cluster runs on top of Galaxy, Parallel Universe’s in-memory data grid.

In this version, clustering is pretty rudimentary, but essential features should work: actors can be made discoverable on the network, messages can be passed among actors on different nodes, and an actor on a failing node will behave as expected of a dying actor with respect to exit messages sent to other, remote, watching it or linked to it.

Enabling Clustering

First, you will need to add quasar-galaxy as a dependency to your project:

[co.paralleluniverse/quasar-galaxy "0.2"]

To make an actor discoverable, all you need to do is register it:

(register actor :global-actor1)

or, if the actor already has a name (set in spawn), simply call:

(register)

That’s it. The actor is now known throughout the cluster. If you want to send a message to it, call

(! :global-actor1 [:hi-from @self])

Though this call looks up the actor in the registry every time it’s called. A better way might be:

(let [a (whereis :global-actor1)]
   (! a [:hi-from @self]))

An actor doesn’t have to be registered in order to be reachable on the network. Registering it simply makes it discoverable. If we pass a local actor in a message to a remote actor, the remote actor will be able to send messages to the local actor as well. In the simple example above, we are sending @self to :global-actor1; :global-actor1 will be able to send messages back to us.

Example

The best way to get started is by running the distributed pingpong example.

Here’s the code for ping and for pong. You run them like this:

lein with-profile cluster update-in :jvm-opts conj '"-Dgalaxy.nodeId=2"' '"-Dgalaxy.port=7052"' '"-Dgalaxy.slave_port=8052"' -- run -m co.paralleluniverse.pulsar.examples.cluster.ping
lein with-profile cluster update-in :jvm-opts conj '"-Dgalaxy.nodeId=1"' '"-Dgalaxy.port=7051"' '"-Dgalaxy.slave_port=8051"' -- run -m co.paralleluniverse.pulsar.examples.cluster.pong

Cluster Configuration

For instructions on how to configure the Galaxy cluster, please refere to Galaxy’s getting started guide.