Lightning.Collaboration.Registry (Lightning v2.14.5-pre1)

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Registry for collaboration processes.

This Registry provides local process tracking for the collaboration system, complementing the cluster-wide :pg process groups. It supports the following key patterns:

Supported Key Patterns

  • {:shared_doc, document_name} - SharedDoc processes for documents (e.g., "workflow:workflow_id")
  • {:persistence_writer, document_name} - PersistenceWriter processes (future use)
  • {:doc_supervisor, workflow_id} - DocumentSupervisor processes (future use)

Session processes are not registered here as there may be multiple sessions for the same workflow and the same user.

Registry vs Process Groups

This Registry is used for local node process lookup and coordination, while :pg (process groups) remains for cluster-wide SharedDoc uniqueness. The Registry provides faster local lookups and better integration with supervision trees.

Usage

Processes can register themselves either in their init callback or using via tuples in their child_spec:

# Session registration in init callback
Lightning.Collaboration.Registry.register({:session, "workflow_123", "user_456"})

# SharedDoc registration via child_spec
{SharedDoc, [
  doc_name: "workflow:workflow_123",
  name: {:via, Registry, {Lightning.Collaboration.Registry.registry_name(), {:shared_doc, "workflow:workflow_123"}}}
]}

Summary

Functions

child_spec(opts)

Child specification for starting the Registry.

count(key \\ nil)
get_group(key)
lookup(key)

Look up all processes registered with the given key.

register(key)

Register the current process with the given key.

select(key)

Select processes registered with the given key (prefix).

via(key)
whereis(key)

Find the pid registered with the given key.

Functions

child_spec(opts)

Child specification for starting the Registry.

count(key \\ nil)

get_group(key)

lookup(key)

@spec lookup(term()) :: [{pid(), term()}]

Look up all processes registered with the given key.

Returns a list of {pid, value} tuples. Since we use unique keys, this will typically return a single-item list or an empty list.

Examples

Lightning.Collaboration.Registry.lookup({:session, "workflow_123"})
# => [{#PID<0.123.0>, nil}]

Lightning.Collaboration.Registry.lookup({:session, "nonexistent"})
# => []

register(key)

@spec register(term()) :: {:ok, pid()} | {:error, {:already_registered, pid()}}

Register the current process with the given key.

Examples

Lightning.Collaboration.Registry.register({:session, "workflow_123"})
# => {:ok, #PID<0.123.0>}

Lightning.Collaboration.Registry.register({:shared_doc, "workflow:workflow_123"})
# => {:ok, #PID<0.123.0>}

Error Cases

Lightning.Collaboration.Registry.register({:session, "workflow_123"})
# => {:error, {:already_registered, #PID<0.456.0>}}

select(key)

@spec select(binary()) :: [{term(), pid()}]

Select processes registered with the given key (prefix).

The key pattern expected is:

  • {:type, key}
  • {:type, key, any()}.

We do a select with any key that starts with the given key.

via(key)

whereis(key)

@spec whereis(term()) :: pid() | nil

Find the pid registered with the given key.

This is a convenience function that returns just the pid, or nil if no process is registered.

Examples

Lightning.Collaboration.Registry.whereis({:session, "workflow_123"})
# => #PID<0.123.0>

Lightning.Collaboration.Registry.whereis({:session, "nonexistent"})
# => nil