refactor(tvix/castore/import): make module, split off fs and error r/7981

Move error types and filesystem-specific functions to a separate file,
and keep the fs:: namespace in public exports.

Change-Id: I5e9e83ad78d9aea38553fafc293d3e4f8c31a8c1
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11486
Tested-by: BuildkiteCI
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Autosubmit: flokli <flokli@flokli.de>

3 files changed, 398 insertions, 0 deletions

diff --git a/tvix/castore/src/import/error.rs b/tvix/castore/src/import/error.rs
new file mode 100644
index 000000000000..15dd0664deaa
--- /dev/null
+++ b/tvix/castore/src/import/error.rs
@@ -0,0 +1,39 @@
+use std::{fs::FileType, path::PathBuf};
+
+use crate::Error as CastoreError;
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("failed to upload directory at {0}: {1}")]
+    UploadDirectoryError(PathBuf, CastoreError),
+
+    #[error("invalid encoding encountered for entry {0:?}")]
+    InvalidEncoding(PathBuf),
+
+    #[error("unable to stat {0}: {1}")]
+    UnableToStat(PathBuf, std::io::Error),
+
+    #[error("unable to open {0}: {1}")]
+    UnableToOpen(PathBuf, std::io::Error),
+
+    #[error("unable to read {0}: {1}")]
+    UnableToRead(PathBuf, std::io::Error),
+
+    #[error("unsupported file {0} type: {1:?}")]
+    UnsupportedFileType(PathBuf, FileType),
+}
+
+impl From<CastoreError> for Error {
+    fn from(value: CastoreError) -> Self {
+        match value {
+            CastoreError::InvalidRequest(_) => panic!("tvix bug"),
+            CastoreError::StorageError(_) => panic!("error"),
+        }
+    }
+}
+
+impl From<Error> for std::io::Error {
+    fn from(value: Error) -> Self {
+        std::io::Error::new(std::io::ErrorKind::Other, value)
+    }
+}
diff --git a/tvix/castore/src/import/fs.rs b/tvix/castore/src/import/fs.rs
new file mode 100644
index 000000000000..a87a0278da4d
--- /dev/null
+++ b/tvix/castore/src/import/fs.rs
@@ -0,0 +1,143 @@
+use std::os::unix::fs::MetadataExt;
+use std::os::unix::fs::PermissionsExt;
+use std::path::Path;
+
+use futures::stream::BoxStream;
+use tracing::instrument;
+use walkdir::DirEntry;
+use walkdir::WalkDir;
+
+use crate::blobservice::BlobService;
+use crate::directoryservice::DirectoryService;
+use crate::proto::node::Node;
+
+use super::ingest_entries;
+use super::upload_blob_at_path;
+use super::Error;
+use super::IngestionEntry;
+
+///! Imports that deal with a real filesystem.
+
+/// Ingests the contents at a given path into the tvix store, interacting with a [BlobService] and
+/// [DirectoryService]. It returns the root node or an error.
+///
+/// It does not follow symlinks at the root, they will be ingested as actual symlinks.
+#[instrument(skip(blob_service, directory_service), fields(path), err)]
+pub async fn ingest_path<BS, DS, P>(
+    blob_service: BS,
+    directory_service: DS,
+    path: P,
+) -> Result<Node, Error>
+where
+    P: AsRef<Path> + std::fmt::Debug,
+    BS: BlobService + Clone,
+    DS: AsRef<dyn DirectoryService>,
+{
+    let entry_stream = walk_path_for_ingestion(blob_service, path.as_ref());
+    ingest_entries(directory_service, entry_stream).await
+}
+
+/// Walk the filesystem at a given path and returns a stream of ingestion entries.
+///
+/// This is how [`ingest_path`] assembles the set of entries to pass on [`ingest_entries`].
+/// This low-level function can be used if additional filtering or processing is required on the
+/// entries.
+///
+/// It does not follow symlinks at the root, they will be ingested as actual symlinks.
+///
+/// This function will walk the filesystem using `walkdir` and will consume
+/// `O(#number of entries)` space.
+#[instrument(fields(path), skip(blob_service))]
+fn walk_path_for_ingestion<'a, BS>(
+    blob_service: BS,
+    path: &'a Path,
+) -> BoxStream<'a, Result<IngestionEntry<'a>, Error>>
+where
+    BS: BlobService + Clone + 'a,
+{
+    let iter = WalkDir::new(path)
+        .follow_links(false)
+        .follow_root_links(false)
+        .contents_first(true)
+        .into_iter();
+
+    dir_entry_iter_to_ingestion_stream(blob_service, iter, path)
+}
+
+/// Converts an iterator of [walkdir::DirEntry]s into a stream of ingestion entries.
+/// This can then be fed into [ingest_entries] to ingest all the entries into the castore.
+///
+/// The root is the [Path] in the filesystem that is being ingested into the castore.
+pub fn dir_entry_iter_to_ingestion_stream<'a, BS, I>(
+    blob_service: BS,
+    iter: I,
+    root: &'a Path,
+) -> BoxStream<'a, Result<IngestionEntry<'a>, Error>>
+where
+    BS: BlobService + Clone + 'a,
+    I: Iterator<Item = Result<DirEntry, walkdir::Error>> + Send + 'a,
+{
+    let prefix = root.parent().unwrap_or_else(|| Path::new(""));
+
+    let iter = iter.map(move |entry| match entry {
+        Ok(entry) => dir_entry_to_ingestion_entry(blob_service.clone(), &entry, prefix),
+        Err(error) => Err(Error::UnableToStat(
+            root.to_path_buf(),
+            error.into_io_error().expect("walkdir err must be some"),
+        )),
+    });
+
+    Box::pin(futures::stream::iter(iter))
+}
+
+/// Converts a [walkdir::DirEntry] into an [IngestionEntry], uploading blobs to the
+/// provided [BlobService].
+///
+/// The prefix path is stripped from the path of each entry. This is usually the parent path
+/// of the path being ingested so that the last element of the stream only has one component.
+fn dir_entry_to_ingestion_entry<'a, BS>(
+    blob_service: BS,
+    entry: &DirEntry,
+    prefix: &Path,
+) -> Result<IngestionEntry<'a>, Error>
+where
+    BS: BlobService + 'a,
+{
+    let file_type = entry.file_type();
+
+    let path = entry
+        .path()
+        .strip_prefix(prefix)
+        .expect("Tvix bug: failed to strip root path prefix")
+        .to_path_buf();
+
+    if file_type.is_dir() {
+        Ok(IngestionEntry::Dir { path })
+    } else if file_type.is_symlink() {
+        let target = std::fs::read_link(entry.path())
+            .map_err(|e| Error::UnableToStat(entry.path().to_path_buf(), e))?;
+
+        Ok(IngestionEntry::Symlink { path, target })
+    } else if file_type.is_file() {
+        let metadata = entry
+            .metadata()
+            .map_err(|e| Error::UnableToStat(entry.path().to_path_buf(), e.into()))?;
+
+        // TODO: In the future, for small files, hash right away and upload async.
+        let digest = Box::pin(upload_blob_at_path(
+            blob_service,
+            entry.path().to_path_buf(),
+        ));
+
+        Ok(IngestionEntry::Regular {
+            path,
+            size: metadata.size(),
+            // If it's executable by the user, it'll become executable.
+            // This matches nix's dump() function behaviour.
+            executable: metadata.permissions().mode() & 64 != 0,
+            digest,
+        })
+    } else {
+        Ok(IngestionEntry::Unknown { path, file_type })
+    }
+}
diff --git a/tvix/castore/src/import/mod.rs b/tvix/castore/src/import/mod.rs
new file mode 100644
index 000000000000..d2b1ee9ff70f
--- /dev/null
+++ b/tvix/castore/src/import/mod.rs
@@ -0,0 +1,216 @@
+//! Deals with ingesting contents into castore.
+//! The main library function here is [ingest_entries], receiving a stream of
+//! [IngestionEntry].
+//!
+//! Specific implementations, such as ingesting from the filesystem, live in
+//! child modules.
+
+use crate::blobservice::BlobService;
+use crate::directoryservice::DirectoryPutter;
+use crate::directoryservice::DirectoryService;
+use crate::proto::node::Node;
+use crate::proto::Directory;
+use crate::proto::DirectoryNode;
+use crate::proto::FileNode;
+use crate::proto::SymlinkNode;
+use crate::B3Digest;
+use futures::Future;
+use futures::{Stream, StreamExt};
+use std::fs::FileType;
+use std::pin::Pin;
+use tracing::Level;
+
+#[cfg(target_family = "unix")]
+use std::os::unix::ffi::OsStrExt;
+
+use std::{
+    collections::HashMap,
+    path::{Path, PathBuf},
+};
+use tracing::instrument;
+
+mod error;
+pub use error::Error;
+
+pub mod fs;
+
+/// Ingests [IngestionEntry] from the given stream into a the passed [DirectoryService].
+/// On success, returns the root [Node].
+///
+/// The stream must have the following invariants:
+/// - All children entries must come before their parents.
+/// - The last entry must be the root node which must have a single path component.
+/// - Every entry should have a unique path.
+///
+/// Internally we maintain a [HashMap] of [PathBuf] to partially populated [Directory] at that
+/// path. Once we receive an [IngestionEntry] for the directory itself, we remove it from the
+/// map and upload it to the [DirectoryService] through a lazily created [DirectoryPutter].
+///
+/// On success, returns the root node.
+#[instrument(skip_all, ret(level = Level::TRACE), err)]
+pub async fn ingest_entries<'a, DS, S>(directory_service: DS, mut entries: S) -> Result<Node, Error>
+where
+    DS: AsRef<dyn DirectoryService>,
+    S: Stream<Item = Result<IngestionEntry<'a>, Error>> + Send + std::marker::Unpin,
+{
+    // For a given path, this holds the [Directory] structs as they are populated.
+    let mut directories: HashMap<PathBuf, Directory> = HashMap::default();
+    let mut maybe_directory_putter: Option<Box<dyn DirectoryPutter>> = None;
+
+    let root_node = loop {
+        let mut entry = entries
+            .next()
+            .await
+            // The last entry of the stream must have 1 path component, after which
+            // we break the loop manually.
+            .expect("Tvix bug: unexpected end of stream")?;
+
+        let name = entry
+            .path()
+            .file_name()
+            // If this is the root node, it will have an empty name.
+            .unwrap_or_default()
+            .as_bytes()
+            .to_owned()
+            .into();
+
+        let node = match &mut entry {
+            IngestionEntry::Dir { .. } => {
+                // If the entry is a directory, we traversed all its children (and
+                // populated it in `directories`).
+                // If we don't have it in there, it's an empty directory.
+                let directory = directories
+                    .remove(entry.path())
+                    // In that case, it contained no children
+                    .unwrap_or_default();
+
+                let directory_size = directory.size();
+                let directory_digest = directory.digest();
+
+                // Use the directory_putter to upload the directory.
+                // If we don't have one yet (as that's the first one to upload),
+                // initialize the putter.
+                maybe_directory_putter
+                    .get_or_insert_with(|| directory_service.as_ref().put_multiple_start())
+                    .put(directory)
+                    .await?;
+
+                Node::Directory(DirectoryNode {
+                    name,
+                    digest: directory_digest.into(),
+                    size: directory_size,
+                })
+            }
+            IngestionEntry::Symlink { ref target, .. } => Node::Symlink(SymlinkNode {
+                name,
+                target: target.as_os_str().as_bytes().to_owned().into(),
+            }),
+            IngestionEntry::Regular {
+                size,
+                executable,
+                digest,
+                ..
+            } => Node::File(FileNode {
+                name,
+                digest: digest.await?.into(),
+                size: *size,
+                executable: *executable,
+            }),
+            IngestionEntry::Unknown { path, file_type } => {
+                return Err(Error::UnsupportedFileType(path.clone(), *file_type));
+            }
+        };
+
+        if entry.path().components().count() == 1 {
+            break node;
+        }
+
+        // record node in parent directory, creating a new [Directory] if not there yet.
+        directories
+            .entry(entry.path().parent().unwrap().to_path_buf())
+            .or_default()
+            .add(node);
+    };
+
+    // if there were directories uploaded, make sure we flush the putter, so
+    // they're all persisted to the backend.
+    if let Some(mut directory_putter) = maybe_directory_putter {
+        let root_directory_digest = directory_putter.close().await?;
+
+        #[cfg(debug_assertions)]
+        {
+            if let Node::Directory(directory_node) = &root_node {
+                debug_assert_eq!(
+                    root_directory_digest,
+                    directory_node
+                        .digest
+                        .to_vec()
+                        .try_into()
+                        .expect("invalid digest len")
+                )
+            } else {
+                unreachable!("Tvix bug: directory putter initialized but no root directory node");
+            }
+        }
+    };
+
+    Ok(root_node)
+}
+
+/// Uploads the file at the provided [Path] the the [BlobService].
+#[instrument(skip(blob_service), fields(path), err)]
+async fn upload_blob_at_path<BS>(blob_service: BS, path: PathBuf) -> Result<B3Digest, Error>
+where
+    BS: BlobService,
+{
+    let mut file = match tokio::fs::File::open(&path).await {
+        Ok(file) => file,
+        Err(e) => return Err(Error::UnableToRead(path, e)),
+    };
+
+    let mut writer = blob_service.open_write().await;
+
+    if let Err(e) = tokio::io::copy(&mut file, &mut writer).await {
+        return Err(Error::UnableToRead(path, e));
+    };
+
+    let digest = writer
+        .close()
+        .await
+        .map_err(|e| Error::UnableToRead(path, e))?;
+
+    Ok(digest)
+}
+
+type BlobFut<'a> = Pin<Box<dyn Future<Output = Result<B3Digest, Error>> + Send + 'a>>;
+
+pub enum IngestionEntry<'a> {
+    Regular {
+        path: PathBuf,
+        size: u64,
+        executable: bool,
+        digest: BlobFut<'a>,
+    },
+    Symlink {
+        path: PathBuf,
+        target: PathBuf,
+    },
+    Dir {
+        path: PathBuf,
+    },
+    Unknown {
+        path: PathBuf,
+        file_type: FileType,
+    },
+}
+
+impl<'a> IngestionEntry<'a> {
+    fn path(&self) -> &Path {
+        match self {
+            IngestionEntry::Regular { path, .. } => path,
+            IngestionEntry::Symlink { path, .. } => path,
+            IngestionEntry::Dir { path } => path,
+            IngestionEntry::Unknown { path, .. } => path,
+        }
+    }
+}