Struct SafeWriter 

pub struct SafeWriter { /* private fields */ }

The ordering znippy’s own hot path already uses, followed rather than re-invented.

Per append, in this order and no other:

1. pwrite the blob bytes at the reserved extent;
2. fsync the blobs — the bytes are on the platter;
3. write one Arrow IPC RecordBatch naming the extent into the journal;
4. flush() the journal’s BufWriter — userspace → kernel;
5. sync_all() the journal file — kernel → platter.

Steps 4 and 5 are not interchangeable and 5 alone is not enough: see the module docs’ “BufWriter trap”. Steps 2 and 3 are not interchangeable either — that is the crash-ordering contract, and crash_between_fsyncs_leaves_orphan_bytes_not_a_dangling_reference asserts it on real files.

Durability on return

The bytes are on the device and a journal row on the device points at them. A crash after return keeps both.

Implementations

impl SafeWriter

pub fn create(archive: &Path) -> Result<Self>

Open archive and start a journal segment beside it at <archive>.journal.

pub fn create_with_faults(archive: &Path, faults: Faults) -> Result<Self>

Same, with an injected fault. Tests only.

pub fn journal_path(archive: &Path) -> PathBuf

Path of the journal segment beside archive.

pub fn blobs(&self) -> &File

The blob file, for a reader that wants to pread an extent back.

pub fn journal_file(&self) -> PathBuf

The journal segment this writer is appending rows to.

Trait Implementations

impl ArchiveWrite for SafeWriter

fn append(&self, bytes: &[u8]) -> Result<Extent>

Append these bytes and return when this implementation’s durability contract is met. Returns the byte extent written.

fn name(&self) -> &'static str

Name it on a bench row.

fn durability(&self) -> &'static str

One-line statement of what a crash immediately after append returns does to the bytes. On the bench table next to the throughput, because a throughput without this is not a comparison.