DCATR.Manifest.Cache (DCAT-R.ex v0.1.0)

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In-memory caching for loaded DCATR.Manifests using ETS.

The cache stores loaded manifests to avoid re-parsing and reloading from files on repeated access.

Architecture

  • GenServer-based: Automatically started by the DCAT-R application supervisor
  • ETS storage: Public ETS table with read concurrency enabled for fast parallel reads
  • Cache key: Tuples of {manifest_type, load_path} ensuring distinct caches per configuration
  • Manual invalidation: No automatic file watching - use invalidate/2 or clear/0 to refresh

Usage

The cache is transparent when using DCATR.Manifest.Cache.manifest/2:

# First call: loads from files and caches
{:ok, manifest} = Cache.manifest(DCATR.Manifest)

# Subsequent calls: returns cached manifest instantly
{:ok, ^manifest} = Cache.manifest(DCATR.Manifest)

# Force reload: bypass cache and refresh
{:ok, new_manifest} = Cache.manifest(DCATR.Manifest, reload: true)

Cache Invalidation

Manual invalidation strategies:

  • Selective invalidation: invalidate(manifest_type, opts) - Invalidates specific manifest
  • Full clear: clear/0 - Removes all cached manifests
  • Reload option: Pass reload: true to manifest/2 - Bypasses cache and updates it
  • Application restart: ETS table is recreated, implicitly clearing cache

Note: There is no automatic file watching or invalidation on file changes.

Summary

Types

cache_key()
state()

GenServer state containing the ETS table reference

Functions

child_spec(init_arg)

Returns a specification to start this module under a supervisor.

clear()

Clears the entire cache.

invalidate(manifest_type, opts \\ [])

Removes a specific manifest from the cache.

manifest(manifest_type, opts \\ [])

Gets a manifest from the cache or loads it if not present or if reload is requested.

start_link(opts \\ [])

Starts the cache GenServer.

Types

cache_key()

@type cache_key() :: {DCATR.Manifest.Type.t(), String.t()}

state()

@type state() :: %{table: :ets.table()}

GenServer state containing the ETS table reference

Functions

child_spec(init_arg)

Returns a specification to start this module under a supervisor.

See Supervisor.

clear()

@spec clear() :: :ok

Clears the entire cache.

Useful for testing purposes.

invalidate(manifest_type, opts \\ [])

@spec invalidate(
  DCATR.Manifest.Type.t(),
  keyword()
) :: :ok

Removes a specific manifest from the cache.

If the manifest is not cached, this is a no-op.

Options

  • :load_path - Custom load path (affects cache key)

manifest(manifest_type, opts \\ [])

@spec manifest(
  DCATR.Manifest.Type.t(),
  keyword()
) :: {:ok, DCATR.Manifest.Type.schema()} | {:error, DCATR.ManifestError.t()}

Gets a manifest from the cache or loads it if not present or if reload is requested.

The cache key is {manifest_type, load_path}, so manifests with different load paths are cached separately.

Options

  • :reload - When true, forces reloading the manifest and updates the cache
  • :load_path - Custom load path (affects cache key)
  • Any other options are passed to DCATR.Manifest.Loader.load/2

start_link(opts \\ [])

@spec start_link(keyword()) :: GenServer.on_start()

Starts the cache GenServer.

This function is called automatically by the DCAT-R application supervisor. The opts are passed to GenServer.start_link/3 but are not used for cache initialization.