libcluster

v2.5.0

libcluster v2.5.0 Cluster.Strategy.Kubernetes.DNS

This clustering strategy works by loading all your Erlang nodes (within Pods) in the current Kubernetes namespace. It will fetch the addresses of all pods under a shared headless service and attempt to connect. It will continually monitor and update its connections every 5s.

It assumes that all Erlang nodes were launched under a base name, are using longnames, and are unique based on their FQDN, rather than the base hostname. In other words, in the following longname, <basename>@<ip>, basename would be the value configured through application_name.

An example configuration is below:

config :libcluster,
  topologies: [
    k8s_example: [
      strategy: Elixir.Cluster.Strategy.Kubernetes.DNS,
      config: [
        service: "myapp-headless",
        application_name: "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

Link to this function child_spec(arg)

Returns a specification to start this module under a supervisor.

See Supervisor.

Link to this function 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.

Link to this function start_link(opts)

Callback implementation for Cluster.Strategy.start_link/1.