# `ImagePipe.Cache.FileSystem`
[🔗](https://github.com/hlindset/image_pipe/blob/v0.2.0/image_pipe/lib/image_pipe/cache/file_system.ex#L1)

Stores processed images, or originals, as files on local disk. The `cache`
and `input_cache` options take its options, and need an instance, which
starts the processes that track the cache's size (see
`ImagePipe.child_spec/1`):

    children = [
      {ImagePipe,
       name: MyApp.Images,
       sources: sources,
       cache: [root: "/var/cache/image_pipe/processed", max_size_bytes: 5_000_000_000]},
      MyAppWeb.Endpoint
    ]

`:max_size_bytes` caps the stored bodies: a write evicts entries to make
room before it's stored, or is rejected. The cache keeps the entries that
are requested often and took the most work to make for their size.

To set up processed-image and originals caches, see
[Caching processed images](caching-processed-images.md).

## Options

* `:root` (absolute path (`t:String.t/0`)) - Required. Directory that holds the cache files. Must be an absolute path. The `cache` and `input_cache` roots must be separate, neither inside the other. Plug initialization fails otherwise.

* `:pool` (`:input` or `:output`) - Tags the cache's telemetry events with `pool`, so events from an originals cache can be told apart from the processed-image cache. Defaults to `:output`, or `:input` for a cache configured as `:input_cache`.

* `:max_size_bytes` (`t:pos_integer/0`) - Required. Cap, in bytes, on the total size of stored bodies. Writes evict the entries least worth keeping to stay under it: those requested least often and quickest to make for their size. An entry larger than a twentieth of the cap, or 256 MiB, is never stored.

The processed-image cache also accepts `:max_body_bytes`, a
non-negative integer or `nil`. Responses larger than `:max_body_bytes` are
delivered but not stored. The default `nil` stores responses of any size.

# `get`

Reads a cached response and materializes its complete body as a binary.

Returns `{:hit, entry}`, `:miss`, or `{:error, reason}`. The cached file's
size is checked before reading, and its descriptor is closed before returning.

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*Consult [api-reference.md](api-reference.md) for complete listing*