Horde v0.7.1 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 start_link(init_arg, options \ [])
    Horde.Registry.start_link(__MODULE__, init_arg, options)

  def init(init_arg) do
    [members: members()]
    |> Keyword.merge(init_arg)
    |> Horde.Registry.init()

  defp members() do
    # ...

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.

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option() View Source
option() ::
  {:keys, :unique}
  | {:name, atom()}
  | {:delta_crdt_options, [DeltaCrdt.crdt_option()]}
  | {:members, [Horde.Cluster.member()]}

Link to this section Functions

See start_link/2 for options.

See Registry.count/1.

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count_match(registry, key, pattern, guards \\ []) View Source

See Registry.count_match/4.

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dispatch(registry, key, mfa_or_fun, opts \\ []) View Source

See Registry.dispatch/4.

Works like Registry.init/1.

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keys(registry, pid) View Source
keys(registry :: Registry.registry(), pid()) :: [Registry.key()]

See Registry.keys/2.

See Registry.lookup/2.

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match(registry, key, pattern, guards \\ []) View Source

See Registry.match/4.

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

See Registry.meta/2.

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put_meta(registry, key, value) View Source
  registry :: Registry.registry(),
  key :: Registry.meta_key(),
  value :: Registry.meta_value()
) :: :ok

See Registry.put_meta/3.

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register(registry, name, value) View Source
  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.select/2.

See Registry.start_link/1.

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

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start_link(mod, init_arg, opts \\ []) View Source

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stop(supervisor, reason \\ :normal, timeout \\ 5000) View Source
stop(Supervisor.supervisor(), reason :: term(), timeout()) :: :ok

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unregister(registry, name) View Source
unregister(registry :: Registry.registry(), name :: Registry.key()) :: :ok

See Registry.unregister/2.

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unregister_match(registry, key, pattern, guards \\ []) View Source

See Registry.unregister_match/4.

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update_value(registry, key, callback) View Source

See Registry.update_value/3.

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child_spec(options) View Source
child_spec(options :: [option()]) :: Supervisor.child_spec()

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init(options) View Source
init(options :: Keyword.t()) :: {:ok, options :: Keyword.t()}