beae3a4bf1
These describe the castore data model, so it should live in the castore crate. Also, some minor edits to //tvix/store/docs/api.md, to honor the move of the castore bits to tvix-castore. Change-Id: I1836556b652ac0592336eac95a8d0647599f4aec Reviewed-on: https://cl.tvl.fyi/c/depot/+/9893 Autosubmit: flokli <flokli@flokli.de> Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
50 lines
1.9 KiB
Markdown
50 lines
1.9 KiB
Markdown
# Data model
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This provides some more notes on the fields used in castore.proto.
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See `//tvix/store/docs/api.md` for the full context.
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## Directory message
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`Directory` messages use the blake3 hash of their canonical protobuf
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serialization as its identifier.
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A `Directory` message contains three lists, `directories`, `files` and
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`symlinks`, holding `DirectoryNode`, `FileNode` and `SymlinkNode` messages
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respectively. They describe all the direct child elements that are contained in
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a directory.
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All three message types have a `name` field, specifying the (base)name of the
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element (which MUST not contain slashes or null bytes, and MUST not be '.' or '..').
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For reproducibility reasons, the lists MUST be sorted by that name and also
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MUST be unique across all three lists.
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In addition to the `name` field, the various *Node messages have the following
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fields:
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## DirectoryNode
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A `DirectoryNode` message represents a child directory.
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It has a `digest` field, which points to the identifier of another `Directory`
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message, making a `Directory` a merkle tree (or strictly speaking, a graph, as
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two elements pointing to a child directory with the same contents would point
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to the same `Directory` message.
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There's also a `size` field, containing the (total) number of all child
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elements in the referenced `Directory`, which helps for inode calculation.
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## FileNode
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A `FileNode` message represents a child (regular) file.
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Its `digest` field contains the blake3 hash of the file contents. It can be
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looked up in the `BlobService`.
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The `size` field contains the size of the blob the `digest` field refers to.
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The `executable` field specifies whether the file should be marked as
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executable or not.
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## SymlinkNode
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A `SymlinkNode` message represents a child symlink.
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In addition to the `name` field, the only additional field is the `target`,
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which is a string containing the target of the symlink.
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