libcluster v2.5.0 Cluster.Strategy.Rancher

This clustering strategy is specific to the Rancher container platform. It works by querying the platform’s metadata API for containers belonging to the same service as the node and attempts to connect them. (see: http://rancher.com/docs/rancher/latest/en/rancher-services/metadata-service/)

It assumes that all nodes share a base name and are using longnames of the form <basename@<ip> where the <ip> is unique for each node.

A way to assign a name to a node on boot in an app running as a Distillery release is:

Create a wrapper script which will interpolate the current ip of the container.

#!/bin/sh

export CONTAINER_IP="$(hostname -I | cut -f1 -d' ')"
export REPLACE_OS_VARS=true

/app/bin/app "$@"

# vm.args
-name app@${CONTAINER_IP}

An example configuration is below:

config :libcluster,
  topologies: [
    rancher_example: [
      strategy: Elixir.Cluster.Strategy.Rancher,
      config: [
        node_basename: "myapp",
        polling_interval: 10_000]]]

Link to this section Summary

Functions

child_spec(arg)

Returns a specification to start this module under a supervisor

init(opts)

Invoked when the server is started. start_link/3 or start/3 will block until it returns

start_link(opts)

Callback implementation for Cluster.Strategy.start_link/1

Link to this section Functions

child_spec(arg)

Returns a specification to start this module under a supervisor.

See Supervisor.

init(opts)

Invoked when the server is started. start_link/3 or start/3 will block until it returns.

args is the argument term (second argument) passed to start_link/3.

Returning {:ok, state} will cause start_link/3 to return {:ok, pid} and the process to enter its loop.

Returning {:ok, state, timeout} is similar to {:ok, state} except handle_info(:timeout, state) will be called after timeout milliseconds if no messages are received within the timeout.

Returning {:ok, state, :hibernate} is similar to {:ok, state} except the process is hibernated before entering the loop. See c:handle_call/3 for more information on hibernation.

Returning :ignore will cause start_link/3 to return :ignore and the process will exit normally without entering the loop or calling c:terminate/2. If used when part of a supervision tree the parent supervisor will not fail to start nor immediately try to restart the GenServer. The remainder of the supervision tree will be (re)started and so the GenServer should not be required by other processes. It can be started later with Supervisor.restart_child/2 as the child specification is saved in the parent supervisor. The main use cases for this are:

The GenServer is disabled by configuration but might be enabled later.
An error occurred and it will be handled by a different mechanism than the Supervisor. Likely this approach involves calling Supervisor.restart_child/2 after a delay to attempt a restart.

Returning {:stop, reason} will cause start_link/3 to return {:error, reason} and the process to exit with reason reason without entering the loop or calling c:terminate/2.

Callback implementation for GenServer.init/1.

start_link(opts)

Callback implementation for Cluster.Strategy.start_link/1.