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diff --git a/docs/media_repository.md b/docs/media_repository.md index 99ee8f1ef7..ba17f8a856 100644 --- a/docs/media_repository.md +++ b/docs/media_repository.md @@ -2,29 +2,80 @@ *Synapse implementation-specific details for the media repository* -The media repository is where attachments and avatar photos are stored. -It stores attachment content and thumbnails for media uploaded by local users. -It caches attachment content and thumbnails for media uploaded by remote users. +The media repository + * stores avatars, attachments and their thumbnails for media uploaded by local + users. + * caches avatars, attachments and their thumbnails for media uploaded by remote + users. + * caches resources and thumbnails used for + [URL previews](development/url_previews.md). -## Storage +All media in Matrix can be identified by a unique +[MXC URI](https://spec.matrix.org/latest/client-server-api/#matrix-content-mxc-uris), +consisting of a server name and media ID: +``` +mxc://<server-name>/<media-id> +``` -Each item of media is assigned a `media_id` when it is uploaded. -The `media_id` is a randomly chosen, URL safe 24 character string. +## Local Media +Synapse generates 24 character media IDs for content uploaded by local users. +These media IDs consist of upper and lowercase letters and are case-sensitive. +Other homeserver implementations may generate media IDs differently. -Metadata such as the MIME type, upload time and length are stored in the -sqlite3 database indexed by `media_id`. +Local media is recorded in the `local_media_repository` table, which includes +metadata such as MIME types, upload times and file sizes. +Note that this table is shared by the URL cache, which has a different media ID +scheme. -Content is stored on the filesystem under a `"local_content"` directory. +### Paths +A file with media ID `aabbcccccccccccccccccccc` and its `128x96` `image/jpeg` +thumbnail, created by scaling, would be stored at: +``` +local_content/aa/bb/cccccccccccccccccccc +local_thumbnails/aa/bb/cccccccccccccccccccc/128-96-image-jpeg-scale +``` -Thumbnails are stored under a `"local_thumbnails"` directory. +## Remote Media +When media from a remote homeserver is requested from Synapse, it is assigned +a local `filesystem_id`, with the same format as locally-generated media IDs, +as described above. -The item with `media_id` `"aabbccccccccdddddddddddd"` is stored under -`"local_content/aa/bb/ccccccccdddddddddddd"`. Its thumbnail with width -`128` and height `96` and type `"image/jpeg"` is stored under -`"local_thumbnails/aa/bb/ccccccccdddddddddddd/128-96-image-jpeg"` +A record of remote media is stored in the `remote_media_cache` table, which +can be used to map remote MXC URIs (server names and media IDs) to local +`filesystem_id`s. -Remote content is cached under `"remote_content"` directory. Each item of -remote content is assigned a local `"filesystem_id"` to ensure that the -directory structure `"remote_content/server_name/aa/bb/ccccccccdddddddddddd"` -is appropriate. Thumbnails for remote content are stored under -`"remote_thumbnail/server_name/..."` +### Paths +A file from `matrix.org` with `filesystem_id` `aabbcccccccccccccccccccc` and its +`128x96` `image/jpeg` thumbnail, created by scaling, would be stored at: +``` +remote_content/matrix.org/aa/bb/cccccccccccccccccccc +remote_thumbnail/matrix.org/aa/bb/cccccccccccccccccccc/128-96-image-jpeg-scale +``` +Older thumbnails may omit the thumbnailing method: +``` +remote_thumbnail/matrix.org/aa/bb/cccccccccccccccccccc/128-96-image-jpeg +``` + +Note that `remote_thumbnail/` does not have an `s`. + +## URL Previews +See [URL Previews](development/url_previews.md) for documentation on the URL preview +process. + +When generating previews for URLs, Synapse may download and cache various +resources, including images. These resources are assigned temporary media IDs +of the form `yyyy-mm-dd_aaaaaaaaaaaaaaaa`, where `yyyy-mm-dd` is the current +date and `aaaaaaaaaaaaaaaa` is a random sequence of 16 case-sensitive letters. + +The metadata for these cached resources is stored in the +`local_media_repository` and `local_media_repository_url_cache` tables. + +Resources for URL previews are deleted after a few days. + +### Paths +The file with media ID `yyyy-mm-dd_aaaaaaaaaaaaaaaa` and its `128x96` +`image/jpeg` thumbnail, created by scaling, would be stored at: +``` +url_cache/yyyy-mm-dd/aaaaaaaaaaaaaaaa +url_cache_thumbnails/yyyy-mm-dd/aaaaaaaaaaaaaaaa/128-96-image-jpeg-scale +``` |