Horde v0.6.0 Horde.Registry behaviour View Source

A distributed process registry.

Horde.Registry implements a distributed Registry backed by a δ-CRDT (provided by DeltaCrdt). This CRDT is used for both tracking membership of the cluster and implementing the registry functionality itself. Local changes to the registry will automatically be synced to other nodes in the cluster.

Cluster membership is managed with Horde.Cluster. Joining a cluster can be done with Horde.Cluster.set_members/2. To take a node out of the cluster, call Horde.Cluster.set_members/2 without that node in the list.

Horde.Registry supports the common “via tuple”, described in the documentation for GenServer.

Horde.Registry is API-compatible with Registry, with the following exceptions:

  • Horde.Registry does not support keys: :duplicate.
  • Horde.Registry does not support partitions.
  • Horde.Registry sends an exit signal to a process when it has lost a naming conflict. See Horde.Registry.register/3 for details.

Module-based Registry

Horde supports module-based registries to enable dynamic runtime configuration.

defmodule MyRegistry do
  use Horde.Registry

  def init(options) do
    {:ok, Keyword.put(options, :members, get_members())}
  end

  defp get_members() do
    # ...
  end
end

Then you can use MyRegistry.child_spec/1 and MyRegistry.start_link/1 in the same way as you’d use Horde.Registry.child_spec/1 and Horde.Registry.start_link/1.

Link to this section Summary

Link to this section Functions

Link to this function child_spec(options \\ []) View Source
child_spec(options :: list()) :: Supervisor.child_spec()

Child spec to enable easy inclusion into a supervisor.

Example:

supervise([
  Horde.Registry
])

Example:

supervise([
  {Horde.Registry, [name: MyApp.GlobalRegistry]}
])
Link to this function count_match(registry, key, pattern, guards \\ []) View Source

See Registry.count_match/4.

Link to this function dispatch(registry, key, mfa_or_fun, opts \\ []) View Source

See Registry.dispatch/4.

Link to this function keys(registry, pid) View Source
keys(registry :: Registry.registry(), pid()) :: [Registry.key()]

See Registry.keys/2.

Link to this function match(registry, key, pattern, guards \\ []) View Source

See Registry.match/4.

Link to this function meta(registry, key) View Source
meta(registry :: Registry.registry(), key :: Registry.meta_key()) ::
  {:ok, Registry.meta_value()} | :error

See Registry.meta/2.

Link to this function put_meta(registry, key, value) View Source
put_meta(
  registry :: Registry.registry(),
  key :: Registry.meta_key(),
  value :: Registry.meta_value()
) :: :ok

See Registry.put_meta/3.

Link to this function register(registry, name, value) View Source
register(
  registry :: Registry.registry(),
  name :: Registry.key(),
  value :: Registry.value()
) :: {:ok, pid()} | {:error, :already_registered, pid()}

Register a process under the given name. See Registry.register/3.

When 2 clustered registries register the same name at exactly the same time, it will seem like name registration succeeds for both registries. The function returns {:ok, pid} for both of these calls.

However, due to the eventually consistent nature of the CRDT, conflict resolution will take place, and the CRDT will pick one of the two processes as the “winner” of the name. The losing process will be sent an exit signal (using Process.exit/2) with the following reason:

{:name_conflict, {name, value}, registry_name, winning_pid}

When two registries are joined using Horde.Cluster.set_members/2, this name conflict message can also occur.

When a cluster is recovering from a netsplit, this name conflict message can also occur.

See Registry.start_link/1.

Does not accept [partitions: x], nor [keys: :unique] as options.

Link to this function stop(supervisor, reason \\ :normal, timeout \\ 5000) View Source
stop(Supervisor.supervisor(), reason :: term(), timeout()) :: :ok
Link to this function unregister(registry, name) View Source
unregister(registry :: Registry.registry(), name :: Registry.key()) :: :ok

See Registry.unregister/2.

Link to this function unregister_match(registry, key, pattern, guards \\ []) View Source

See Registry.unregister_match/4.

Link to this function update_value(registry, key, callback) View Source

See Registry.update_value/3.

Link to this section Callbacks

Link to this callback init(options) View Source
init(options :: Keyword.t()) :: {:ok, options :: Keyword.t()}