I am experimenting with how to capture a Livebook connection in a cluster. I run clustered containers: 2 Phoenix nodes and a Livebook to monitor the web app. I can’t capture the Livebook “nodeup” (or down) event in the web apps.
I use libcluster in Gossip mode. It is set in the web app and in the Livebook (see below). The 3 nodes are clustered: I have connection logs from libcluster and I can :rpc.call a Phoenix node from the LB.
However, libcluster sends only logs: [info] [libcluster:gossip] connected to... but no event.
I use :net_kernel.monitor_nodes(true) in the web app but this only captures the Phoenix nodes events, not the Livebook node.
I tried to use Phoenix.PubSub with the registered MyApp.PubSub in the Livebook to push a message once connected: I have a subscription in a module of the web app to a topic, set up a “catch all” handle_info on this topic. However, the broadcasted message from the Livebook is not received?/captured? in the web app. Is this a config (naming) problem?
The Livebook image (GitHub - livebook-dev/livebook: Automate code & data workflows with interactive Elixir notebooks) contains:
Mix.install ([
{:libcluster, "~> 3.3.3"},
{:phoenix_pubsub, "~> 2.1"}
])
topologies = [gossip: [strategy: Cluster.Strategy.Gossip]]
opts = [strategy: :one_for_one, name: MyApp.Supervisor]
children = [
{Phoenix.PubSub, name: MyApp.PubSub},
{Cluster.Supervisor, [topologies, [name: MyApp.ClusterSupervisor]]}
]
Supervisor.start_link(children, opts)
Phoenix.PubSub.broadcast(MyApp.PubSub, "nodes", {:up, node()})
In a GenServer module in the web app:
def init(_) do
:net_kernel.monitor_nodes(true)
Phoenix.PubSub.subscribe(MyApp.PubSub, "nodes")
{:ok, nil}
def handle_info({:nodeup, node}, _state) do
# this is ok between web apps
{:noreply, nil}
def handle_info(msg, _state) do
# !! no message on the "nodes" topic is captured here
{:noreply, nil}
The docker-compose service for the Livebook is:
livebook:
image: ghcr.io/livebook-dev/livebook
networks:
- mynet
environment:
# - MIX_ENV=prod
- LIVEBOOK_DISTRIBUTION=name
- LIVEBOOK_COOKIE=supersecret
- LIVEBOOK_PASSWORD=securesecret
- LIVEBOOK_NODE=livebook
hostname: livebook.mynet
volumes:
- ./data:/data/
- ./db:/db
ports:
- "8080:8080"
- "8081:8081"
