Tracks the active log file for each shard.
Uses a per-row atomics generation counter plus a process dictionary cache.
Reads stay one Process.get/1 plus one :atomics.get/2 on the hot path,
while a rotation invalidates only callers that cached that exact shard.
Usage
# In Shard init and rotation:
ActiveFile.publish(instance_ctx, shard_index, file_id, file_path, shard_data_path)
# In Router's local-origin write path (hot path):
{file_id, file_path, shard_data_path} = ActiveFile.get(instance_ctx, shard_index)Summary
Functions
Removes active-file rows for a custom instance.
Returns {file_id, file_path, shard_data_path} for the given shard.
Returns active file metadata for a shard in a specific instance.
Ensures the supervised active-file registry is available.
Publishes the active file metadata for a shard.
Publishes active file metadata for a shard in a specific instance.
Functions
@spec cleanup_instance(map()) :: :ok
Removes active-file rows for a custom instance.
Called during instance cleanup. The generation bump invalidates process dictionary caches that may still hold paths for the stopped instance.
@spec get(non_neg_integer()) :: {non_neg_integer(), binary(), binary()}
Returns {file_id, file_path, shard_data_path} for the given shard.
~15ns hot path (atomics check + process dictionary cache hit). ~100ns cold (ETS lookup on generation mismatch).
@spec get(map() | nil, non_neg_integer()) :: {non_neg_integer(), binary(), binary()}
Returns active file metadata for a shard in a specific instance.
Prefer this in production paths that already have an Instance context.
@spec init(non_neg_integer()) :: :ok | {:error, :table_owner_unavailable}
Ensures the supervised active-file registry is available.
@spec publish(non_neg_integer(), non_neg_integer(), binary(), binary()) :: :ok
Publishes the active file metadata for a shard.
Called from Shard.init/1 and Shard.maybe_rotate_file/1.
@spec publish(map() | nil, non_neg_integer(), non_neg_integer(), binary(), binary()) :: :ok
Publishes active file metadata for a shard in a specific instance.
Every instance uses {instance_name, shard_index} so registry identity is
uniform across default and embedded stores.