Struct SnapshotFsWriter 

pub struct SnapshotFsWriter { /* private fields */ }

A file system backed snapshot writer using atomic write-to-temp-then-rename.

The writer opens a temporary sibling file (target path + .tmp suffix) and writes encoded snapshot data to it using the same framing format as the WAL (version + length + crc32 + payload). On close(), the temp file is flushed, renamed atomically over the target path, and the parent directory is fsynced. If the writer is dropped without calling close(), the temp file is removed and the original snapshot (if any) remains intact.

Implementations

impl SnapshotFsWriter

pub fn new(path: PathBuf) -> Result<Self, SnapshotFsWriterInitError>

Creates a new snapshot writer at the given path.

Instead of opening the target path directly, a temporary sibling file (target path with .tmp suffix appended) is created and written to. The target file is only replaced atomically when close() is called, ensuring crash safety.

Arguments

• path - The filesystem path where the snapshot file should ultimately reside

Errors

Returns SnapshotFsWriterInitError::IoError if the temporary file cannot be created or opened for writing.

Trait Implementations

impl Drop for SnapshotFsWriter

fn drop(&mut self)

Executes the destructor for this type.

impl SnapshotWriter for SnapshotFsWriter

fn write(&mut self, snapshot: &Snapshot) -> Result<(), SnapshotWriterError>

Write a snapshot to storage.

The snapshot is encoded using the same framing format as the WAL:

• 4 bytes version (currently 4)
• 4 bytes length of payload
• 4 bytes CRC-32 of payload
• JSON-serialized Snapshot

Arguments

• snapshot - The snapshot to write

Errors

Returns SnapshotWriterError::Closed if the writer has been closed. Returns SnapshotWriterError::IoError if the write operation fails. Returns SnapshotWriterError::EncodeError if serialization fails.

fn flush(&mut self) -> Result<(), SnapshotWriterError>

Flushes pending writes to durable storage.

This ensures that all buffered data is written to disk before returning. The flush operation is synchronous and will block until the data is persisted.

Errors

Returns SnapshotWriterError::Closed if the writer has been closed. Returns SnapshotWriterError::IoError if the flush operation fails.

fn close(self) -> Result<(), SnapshotWriterError>

Closes the writer, atomically replacing the target snapshot file.

This performs:

1. sync_all() on the temp file to ensure data is durable
2. rename(temp, target) for atomic replacement
3. fsync on the parent directory to make the rename durable

Once closed, the writer cannot be used for further operations. If close() is not called (e.g. due to a crash or error), the temp file is cleaned up on drop and the original snapshot is preserved.

Errors

Returns SnapshotWriterError::IoError if the flush, rename, or directory sync operation fails.