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Copy pathwal.rs
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1449 lines (1292 loc) · 55.4 KB
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//! Write-Ahead Log (WAL) for Minigraf.
//!
//! The WAL sidecar file (`<db>.wal`) stores committed transaction entries as
//! CRC32-protected binary records. Facts go to the WAL before the main file,
//! ensuring crash safety.
//!
//! # File layout
//!
//! ```text
//! WAL header (32 bytes):
//! magic: [u8; 4] = b"MWAL"
//! version: u32 LE = 2
//! base_generation: u64 LE generation of the meta page that was active when
//! this WAL was created (v2; spec §4.1.1)
//! reserved: [u8; 16]
//!
//! A version 1 header (v2.x) has no base_generation. It can only sit next to a
//! file migrated from format v7 whose next checkpoint has not completed, so it
//! reads as base generation 1.
//!
//! WAL entries (variable length, sequential):
//! checksum: u32 LE CRC32 of everything after this field in this entry
//! tx_count: u64 LE monotonic counter from FactStorage
//! num_facts: u64 LE
//! facts: for each fact: fact_len: u32 LE | fact_bytes: [u8; fact_len]
//! ```
use crate::db::SyncMode;
use crate::error::{ErrorCode, bail_coded, err_coded};
use crate::graph::types::{Fact, Value};
use crate::storage::dir_sync::sync_parent_dir;
#[cfg(test)]
use crate::storage::fault::{self, Action, Site};
use crate::storage::keys::{MAX_IDENT_BYTES, MAX_VALUE_BYTES, set_bytes_bound};
use anyhow::Result;
use std::fs::{File, OpenOptions};
use std::io::{self, Read, Seek, SeekFrom, Write};
use std::path::Path;
const WAL_MAGIC: [u8; 4] = *b"MWAL";
const WAL_VERSION: u32 = 2;
/// Format v7 (Minigraf v2.x) WAL version, read as base generation 1.
const WAL_VERSION_V1: u32 = 1;
const WAL_HEADER_SIZE: usize = 32;
// ─── WAL Header ─────────────────────────────────────────────────────────────
fn write_wal_header(file: &mut File, base_generation: u64) -> Result<()> {
let mut buf = [0u8; WAL_HEADER_SIZE];
buf[0..4].copy_from_slice(&WAL_MAGIC);
buf[4..8].copy_from_slice(&WAL_VERSION.to_le_bytes());
buf[8..16].copy_from_slice(&base_generation.to_le_bytes());
// bytes 16..32 are reserved zeros
file.seek(SeekFrom::Start(0))?;
wal_write(file, &buf)?;
wal_sync(file, true, 0)?;
Ok(())
}
/// Write `bytes` at the file's position. Every WAL byte goes through here.
fn wal_write(file: &mut File, bytes: &[u8]) -> io::Result<()> {
#[cfg(test)]
match fault::on(Site::WalWrite) {
Action::Fail(e) => return Err(e),
Action::Tear(n) => {
file.write_all(&bytes[..n.min(bytes.len())])?;
return Err(fault::eio());
}
Action::Proceed | Action::Lose => {}
}
file.write_all(bytes)
}
/// Sync the WAL (`sync_all` when `all`, else `sync_data`). `synced_len` is
/// its length at the last good sync: a test fault that loses unsynced
/// writes cuts the file back to it.
#[cfg_attr(not(test), allow(unused_variables))]
fn wal_sync(file: &mut File, all: bool, synced_len: u64) -> io::Result<()> {
#[cfg(test)]
match fault::on(Site::WalSync) {
Action::Fail(e) => return Err(e),
Action::Lose => {
file.set_len(synced_len)?;
return Err(fault::eio());
}
Action::Proceed | Action::Tear(_) => {}
}
if all {
file.sync_all()
} else {
file.sync_data()
}
}
/// Check magic and version and return the header's base generation.
fn validate_wal_header(file: &mut File) -> Result<u64> {
let mut buf = [0u8; WAL_HEADER_SIZE];
file.seek(SeekFrom::Start(0))?;
file.read_exact(&mut buf)?;
if buf[0..4] != WAL_MAGIC {
bail_coded!(ErrorCode::Wal001);
}
let version = u32::from_le_bytes([buf[4], buf[5], buf[6], buf[7]]);
match version {
WAL_VERSION => {
let mut base = [0u8; 8];
base.copy_from_slice(&buf[8..16]);
Ok(u64::from_le_bytes(base))
}
WAL_VERSION_V1 => Ok(1),
_ => bail_coded!(ErrorCode::Wal002, version, WAL_VERSION),
}
}
/// Whether an existing WAL file's header is intact, or too short to
/// contain one at all.
enum WalHeaderState {
/// At least `WAL_HEADER_SIZE` bytes present; validated by
/// `validate_wal_header` (magic/version checked separately).
Present,
/// Fewer than `WAL_HEADER_SIZE` bytes on disk. This can only happen
/// from a crash between `create_new` and `write_wal_header` completing
/// in `WalWriter::open_or_create` -- before any `WalWriter` existed to
/// append an entry with. Safe to treat as an empty WAL (#308-class
/// fix: the same "kill mid multi-step file write" window that
/// corrupted the main `.graph` header applies here to the WAL sidecar).
Absent,
}
/// Distinguishes a too-short WAL file from one long enough to validate.
/// Does not itself validate magic/version -- callers still run
/// `validate_wal_header` on the `Present` case.
fn check_wal_header_length(file: &mut File) -> Result<WalHeaderState> {
let len = file.metadata()?.len();
if len < WAL_HEADER_SIZE as u64 {
Ok(WalHeaderState::Absent)
} else {
Ok(WalHeaderState::Present)
}
}
// ─── Entry serialization ────────────────────────────────────────────────────
/// Reject a fact a checkpoint could not store (WAL-003): a string value longer
/// than one value page's payload, a set whose element encoding may be longer
/// (#316), or an attribute or keyword (a set's keyword elements too) longer
/// than an ident may be (spec §6.3).
pub(crate) fn check_fact_size(fact: &Fact) -> Result<()> {
if fact.attribute.len() > MAX_IDENT_BYTES {
bail_coded!(ErrorCode::Wal003, fact.attribute.len(), MAX_IDENT_BYTES);
}
match &fact.value {
Value::String(s) if s.len() > MAX_VALUE_BYTES => {
bail_coded!(ErrorCode::Wal003, s.len(), MAX_VALUE_BYTES)
}
Value::Keyword(k) if k.len() > MAX_IDENT_BYTES => {
bail_coded!(ErrorCode::Wal003, k.len(), MAX_IDENT_BYTES)
}
Value::Set(set) => {
for e in set {
if let Value::Keyword(k) = e
&& k.len() > MAX_IDENT_BYTES
{
bail_coded!(ErrorCode::Wal003, k.len(), MAX_IDENT_BYTES)
}
}
let n = set_bytes_bound(set);
if n > MAX_VALUE_BYTES {
bail_coded!(ErrorCode::Wal003, n, MAX_VALUE_BYTES)
}
Ok(())
}
_ => Ok(()),
}
}
fn serialize_entry(tx_count: u64, facts: &[Fact]) -> Result<Vec<u8>> {
// Build payload (everything covered by the checksum)
let mut payload: Vec<u8> = Vec::new();
payload.extend_from_slice(&tx_count.to_le_bytes());
payload.extend_from_slice(&(facts.len() as u64).to_le_bytes());
for fact in facts {
check_fact_size(fact)?;
let fact_bytes = postcard::to_allocvec(fact)?;
let fact_len = u32::try_from(fact_bytes.len())
.map_err(|_| err_coded!(ErrorCode::Wal004, fact_bytes.len()))?;
payload.extend_from_slice(&fact_len.to_le_bytes());
payload.extend_from_slice(&fact_bytes);
}
let checksum = crc32fast::hash(&payload);
let mut entry = Vec::with_capacity(payload.len().saturating_add(4));
entry.extend_from_slice(&checksum.to_le_bytes());
entry.extend_from_slice(&payload);
Ok(entry)
}
// ─── Public types ───────────────────────────────────────────────────────────
/// A single committed transaction entry read from the WAL.
#[derive(Debug)]
pub struct WalEntry {
pub tx_count: u64,
pub facts: Vec<Fact>,
}
// ─── WalWriter ──────────────────────────────────────────────────────────────
/// Appends committed transaction entries to the WAL sidecar file.
///
/// Created by `Minigraf::open()` for file-backed databases.
/// Not used for in-memory databases. The writer keeps no [`SyncMode`]: each
/// append is given its own, so one transaction's mode never reaches the next
/// (#871).
pub struct WalWriter {
file: File,
/// An append failed, so the file may end in a partial entry. Later
/// appends would land after it, where replay never reaches (#513).
failed: bool,
/// The file's length after the last successful append (test models only).
#[cfg(test)]
end: u64,
/// The file's length at its last successful sync: what a lost sync or a
/// power loss leaves of it, in the test models. An append without a sync
/// (`SyncMode::Normal`) does not move it.
#[cfg(test)]
synced: u64,
}
impl WalWriter {
/// [`WalWriter::open_or_create_at`] with base generation 1, for tests.
#[cfg(test)]
pub fn open_or_create(path: &Path) -> Result<Self> {
Self::open_or_create_at(path, 1)
}
/// Open an existing WAL or create a new one.
///
/// If creating, writes the WAL header with `base_generation`, the generation
/// of the meta page active now. If opening, validates the header (keeping its
/// base generation) and seeks to the end for appending.
pub fn open_or_create_at(path: &Path, base_generation: u64) -> Result<Self> {
// Try atomic create-new first (no TOCTOU window)
match OpenOptions::new()
.read(true)
.write(true)
.create_new(true)
.open(path)
{
Ok(mut file) => {
8BD0
write_wal_header(&mut file, base_generation)?;
// The header is durable; make the WAL's directory entry
// durable too, or a power loss can lose the whole file (#389).
sync_parent_dir(path)?;
#[cfg_attr(not(test), allow(unused_variables))]
let end = file.seek(SeekFrom::End(0))?;
return Ok(WalWriter {
file,
failed: false,
#[cfg(test)]
end,
#[cfg(test)]
synced: end,
});
}
Err(e) if e.kind() == std::io::ErrorKind::AlreadyExists => {}
Err(e) => return Err(e.into()),
}
// File exists — validate its header and seek to end for appending
let mut file = OpenOptions::new().read(true).write(true).open(path)?;
match check_wal_header_length(&mut file)? {
WalHeaderState::Present => {
validate_wal_header(&mut file)?;
// A crash during an append can leave a partial entry at the
// end. Replay stops there, so an entry appended after it
// would be lost: cut it off before appending (#513).
let (_, valid_end) = scan_entries(&mut file)?;
if file.metadata()?.len() > valid_end {
#[cfg(test)]
if let Action::Fail(e) = fault::on(Site::WalTruncate) {
return Err(e.into());
}
file.set_len(valid_end)?;
// A lost sync here would bring the cut bytes back,
// which the test fault cannot model: it fails instead.
wal_sync(&mut file, true, valid_end)?;
}
}
// A previous crash landed between this file's creation and its
// header write completing; no entry could have been appended
// yet, so re-initialize it as a fresh, empty WAL.
// The crash may also have preceded the directory sync that
// follows creation, so repeat it (#389).
WalHeaderState::Absent => {
write_wal_header(&mut file, base_generation)?;
sync_parent_dir(path)?;
}
}
#[cfg_attr(not(test), allow(unused_variables))]
let end = file.seek(SeekFrom::End(0))?;
Ok(WalWriter {
file,
failed: false,
#[cfg(test)]
end,
// The test models take what an earlier handle left as on disk.
#[cfg(test)]
synced: end,
})
}
/// Whether every byte written to the file has been synced since. Tests
/// use it to see whether a commit synced the WAL.
#[cfg(test)]
pub(crate) fn is_synced(&self) -> bool {
self.synced == self.end
}
/// Cut the file back to its length at its last successful sync, as a
/// power loss would leave it (a test model; #871).
#[cfg(test)]
pub(crate) fn lose_unsynced(&mut self) -> Result<()> {
self.file.set_len(self.synced)?;
self.end = self.synced;
Ok(())
}
/// Serialize `facts` as a WAL entry and append it to the file.
///
/// The entry is written atomically from the caller's perspective:
/// a partial write produces a bad CRC32, which the reader discards.
/// Then flushes to disk, unless `sync` is `SyncMode::Normal` — see [`SyncMode`].
/// A flush covers every earlier entry too, including ones appended
/// without one.
///
/// After a failed write or sync, every later append fails with WAL-007:
/// the file may end in a partial entry, and replay stops there (#513). A
/// new writer (after a checkpoint deletes the WAL, or on reopen) starts
/// clean. Whether the failed entry itself is durable is unknown: it is
/// replayed on reopen if it reached the disk whole, and lost otherwise.
pub fn append_entry(&mut self, tx_count: u64, facts: &[Fact], sync: SyncMode) -> Result<()> {
if self.failed {
bail_coded!(ErrorCode::Wal007);
}
let entry_bytes = serialize_entry(tx_count, facts)?;
let written = self.write_entry(&entry_bytes, sync);
if written.is_err() {
self.failed = true;
}
written
}
fn write_entry(&mut self, entry_bytes: &[u8], sync: SyncMode) -> Result<()> {
wal_write(&mut self.file, entry_bytes)?;
#[cfg(test)]
{
self.end = self.end.saturating_add(entry_bytes.len() as u64);
}
if sync == SyncMode::Full {
// A lost sync loses every write since the last good one, this
// entry and any appended without a sync before it.
#[cfg(test)]
let synced_len = self.synced;
#[cfg(not(test))]
let synced_len = 0;
wal_sync(&mut self.file, false, synced_len)?;
#[cfg(test)]
{
self.synced = self.end;
}
}
Ok(())
}
/// Whether an append failed, so every later one is refused (WAL-007).
pub(crate) fn failed(&self) -> bool {
self.failed
}
/// Delete the WAL file at `path`. Called after a successful checkpoint.
///
/// Fsyncs the parent directory after the remove, so a power loss cannot
/// bring the deleted WAL back (#389).
///
/// Uses a short retry loop to tolerate Windows races where the OS file handle
/// is not immediately released after the `WalWriter` is dropped.
pub fn delete_file(path: &Path) -> Result<()> {
// Retry up to ~500 ms on Windows where handle release can lag drop().
let retries: u32 = if cfg!(windows) { 10 } else { 1 };
let mut last_err = None;
for i in 0..retries {
#[cfg(test)]
if let Action::Fail(e) = fault::on(Site::WalRemove) {
last_err = Some(e);
break;
}
match std::fs::remove_file(path) {
Ok(()) => {
sync_parent_dir(path)?;
return Ok(());
}
Err(e) => {
last_err = Some(e);
if i.saturating_add(1) < retries {
std::thread::sleep(std::time::Duration::from_millis(50));
}
}
}
}
Err(err_coded!(
ErrorCode::Wal006,
path.display(),
last_err
.map(|e| e.to_string())
.unwrap_or_else(|| "unknown error".to_string())
))
}
}
// ─── WalReader ──────────────────────────────────────────────────────────────
/// Reads and validates WAL entries for crash recovery.
pub struct WalReader {
file: File,
base_generation: Option<u64>,
}
impl WalReader {
/// Open the WAL at `path` for reading.
pub fn open(path: &Path) -> Result<Self> {
let mut file = File::open(path)?;
let base_generation = match check_wal_header_length(&mut file)? {
WalHeaderState::Present => Some(validate_wal_header(&mut file)?),
// Too short to contain a header, which can only mean a crash
// landed before any entry was ever appended (see
// `WalHeaderState::Absent`). `read_entries` already treats
// hitting EOF while reading an entry as "no more entries", so
// leaving the file as-is and letting that seek-past-end happen
// naturally is correct -- there is nothing here to replay.
WalHeaderState::Absent => None,
};
Ok(WalReader {
file,
base_generation,
})
}
/// The generation of the meta page active when this WAL was created, or
/// `None` for a header-less WAL (a crash before its header was written, so
/// it holds no entries and counts as no WAL).
pub fn base_generation(&self) -> Option<u64> {
self.base_generation
}
/// Read all valid entries from the WAL.
///
/// Reads sequentially from after the header. Stops at the first entry
/// with an invalid CRC32 (partial write) or at EOF. Earlier entries are
/// unaffected by a bad entry.
pub fn read_entries(&mut self) -> Result<Vec<WalEntry>> {
Ok(scan_entries(&mut self.file)?.0)
}
}
/// Read every valid entry after the header, stopping at the first truncated
/// or corrupt one or at EOF. Also returns the offset where the valid entries
/// end: the end of the header if there are none.
fn scan_entries(file: &mut File) -> Result<(Vec<WalEntry>, u64)> {
// Without the length, a corrupt count still ends at EOF, only later.
let file_len = file.metadata().map_or(u64::MAX, |m| m.len());
file.seek(SeekFrom::Start(WAL_HEADER_SIZE as u64))?;
let mut entries = Vec::new();
let mut valid_end = WAL_HEADER_SIZE as u64;
loop {
// Read checksum (4 bytes); EOF here means no more entries
let mut csum_buf = [0u8; 4];
match file.read_exact(&mut csum_buf) {
Err(e) if e.kind() == io::ErrorKind::UnexpectedEof => break,
Err(e) => return Err(e.into()),
Ok(()) => {}
}
let expected_csum = u32::from_le_bytes(csum_buf);
// Read tx_count (8 bytes)
let mut tx_count_buf = [0u8; 8];
if file.read_exact(&mut tx_count_buf).is_err() {
break; // truncated
}
let tx_count = u64::from_le_bytes(tx_count_buf);
// Read num_facts (8 bytes)
let mut num_facts_buf = [0u8; 8];
if file.read_exact(&mut num_facts_buf).is_err() {
break; // truncated
}
// Every fact takes at least its 4-byte length, so a count the bytes
// left cannot hold is damage. Entries have no count limit (#686).
let num_facts = u64::from_le_bytes(num_facts_buf);
// The entry starts at `valid_end`; its facts after 20 header bytes.
let left = file_len.saturating_sub(valid_end.saturating_add(20));
if num_facts > left / 4 {
break; // treat as corrupt entry
}
let num_facts = usize::try_from(num_facts).map_err(|_| err_coded!(ErrorCode::Wal005))?;
// Maximum fact size to prevent memory exhaustion from large facts
const MAX_FACT_SIZE: usize = 10 * 1024 * 1024; // 10MB
// Build payload for CRC32 verification
let mut payload = Vec::new();
payload.extend_from_slice(&tx_count_buf);
payload.extend_from_slice(&num_facts_buf);
// Read each fact
let mut facts = Vec::new(); // grow dynamically instead of pre-allocating
let mut truncated = false;
for _ in 0..num_facts {
let mut len_buf = [0u8; 4];
if file.read_exact(&mut len_buf).is_err() {
truncated = true;
break;
}
let fact_len = u32::from_le_bytes(len_buf) as usize;
if fact_len > MAX_FACT_SIZE {
truncated = true;
break;
}
payload.extend_from_slice(&len_buf);
let mut fact_bytes = vec![0u8; fact_len];
if file.read_exact(&mut fact_bytes).is_err() {
truncated = true;
break;
}
payload.extend_from_slice(&fact_bytes);
match postcard::from_bytes::<Fact>(&fact_bytes) {
Ok(f) => facts.push(f),
Err(_) => {
truncated = true;
break;
}
}
}
if truncated {
break;
}
// Verify CRC32 over the full payload
let actual_csum = crc32fast::hash(&payload);
if expected_csum != actual_csum {
break; // corrupted entry — stop here
}
entries.push(WalEntry { tx_count, facts });
valid_end = file.stream_position()?;
}
Ok((entries, valid_end))
}
// ─── Unit tests ─────────────────────────────────────────────────────────────
#[cfg(all(test, not(target_arch = "wasm32")))]
mod tests {
use super::*;
use crate::graph::types::{VALID_TIME_FOREVER, Value};
use uuid::Uuid;
fn make_fact(entity: Uuid, attr: &str, value: Value, tx_count: u64) -> Fact {
Fact::with_valid_time(
entity,
attr.to_string(),
value,
1000,
tx_count,
0,
VALID_TIME_FOREVER,
)
}
#[test]
fn test_wal_empty_round_trip() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
let _writer = WalWriter::open_or_create(&path).unwrap();
let mut reader = WalReader::open(&path).unwrap();
let entries = reader.read_entries().unwrap();
assert!(entries.is_empty(), "new WAL should have no entries");
}
#[test]
fn test_wal_single_fact_round_trip() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
let alice = Uuid::new_v4();
let fact = make_fact(alice, ":name", Value::String("Alice".to_string()), 1);
let mut writer = WalWriter::open_or_create(&path).unwrap();
writer
.append_entry(1, std::slice::from_ref(&fact), SyncMode::Full)
.unwrap();
let mut reader = WalReader::open(&path).unwrap();
let entries = reader.read_entries().unwrap();
assert_eq!(entries.len(), 1);
assert_eq!(entries[0].tx_count, 1);
assert_eq!(entries[0].facts.len(), 1);
assert_eq!(entries[0].facts[0].entity, fact.entity);
assert_eq!(entries[0].facts[0].attribute, fact.attribute);
assert_eq!(entries[0].facts[0].value, fact.value);
}
#[test]
fn test_wal_normal_mode_write_and_replay() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
let alice = Uuid::new_v4();
let fact = make_fact(alice, ":name", Value::String("Alice".to_string()), 1);
// Normal mode skips the per-write flush; the entry must still be
// durable-within-process (write_all()'d) and correctly replayable.
let mut writer = WalWriter::open_or_create(&path).unwrap();
writer
.append_entry(1, std::slice::from_ref(&fact), SyncMode::Normal)
.unwrap();
let mut reader = WalReader::open(&path).unwrap();
let entries = reader.read_entries().unwrap();
assert_eq!(entries.len(), 1);
assert_eq!(entries[0].tx_count, 1);
assert_eq!(entries[0].facts.len(), 1);
assert_eq!(entries[0].facts[0].entity, fact.entity);
}
#[test]
fn test_wal_multi_fact_entry_round_trip() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
let alice = Uuid::new_v4();
let facts = vec![
make_fact(alice, ":name", Value::String("Alice".to_string()), 1),
make_fact(alice, ":age", Value::Integer(30), 1),
];
let mut writer = WalWriter::open_or_create(&path).unwrap();
writer.append_entry(1, &facts, SyncMode::Full).unwrap();
let mut reader = WalReader::open(&path).unwrap();
let entries = reader.read_entries().unwrap();
assert_eq!(entries.len(), 1);
assert_eq!(entries[0].facts.len(), 2);
assert_eq!(entries[0].facts[0].entity, facts[0].entity);
assert_eq!(entries[0].facts[0].attribute, facts[0].attribute);
assert_eq!(entries[0].facts[0].value, facts[0].value);
assert_eq!(entries[0].facts[1].entity, facts[1].entity);
assert_eq!(entries[0].facts[1].attribute, facts[1].attribute);
assert_eq!(entries[0].facts[1].value, facts[1].value);
}
#[test]
fn test_wal_multiple_entries_round_trip() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
let alice = Uuid::new_v4();
let bob = Uuid::new_v4();
let mut writer = WalWriter::open_or_create(&path).unwrap();
writer
.append_entry(
1,
&[make_fact(
alice,
":name",
Value::String("Alice".to_string()),
1,
)],
SyncMode::Full,
)
.unwrap();
writer
.append_entry(
2,
&[make_fact(bob, ":name", Value::String("Bob".to_string()), 2)],
SyncMode::Full,
)
.unwrap();
let mut reader = WalReader::open(&path).unwrap();
let entries = reader.read_entries().unwrap();
assert_eq!(entries.len(), 2);
assert_eq!(entries[0].tx_count, 1);
assert_eq!(entries[1].tx_count, 2);
}
#[test]
fn test_wal_reopen_and_append() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
let alice = Uuid::new_v4();
let bob = Uuid::new_v4();
// First open: create WAL and write entry with tx_count=1
let mut writer = WalWriter::open_or_create(&path).unwrap();
writer
.append_entry(
1,
&[make_fact(
alice,
":name",
Value::String("Alice".to_string()),
1,
)],
SyncMode::Full,
)
.unwrap();
drop(writer);
// Second open: exercises the fallback branch (file already exists)
let mut writer = WalWriter::open_or_create(&path).unwrap();
writer
.append_entry(
2,
&[make_fact(bob, ":name", Value::String("Bob".to_string()), 2)],
SyncMode::Full,
)
.unwrap();
drop(writer);
// Read back and verify both entries are present with correct tx_count values
let mut reader = WalReader::open(&path).unwrap();
let entries = reader.read_entries().unwrap();
assert_eq!(entries.len(), 2);
assert_eq!(entries[0].tx_count, 1);
assert_eq!(entries[1].tx_count, 2);
}
#[test]
fn test_wal_bad_magic_rejected() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("bad.wal");
// Write garbage header
std::fs::write(&path, b"XXXX\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00").unwrap();
let result = WalReader::open(&path);
assert!(result.is_err(), "bad magic should be rejected");
}
/// #308-class fix: a crash between `create_new` and the header write
/// finishing in `open_or_create` leaves a WAL file shorter than
/// `WAL_HEADER_SIZE`. No entry could ever have been appended at that
/// point (that requires a fully-open `WalWriter`), so this must be
/// treated as an empty WAL rather than a hard read error.
#[test]
fn test_wal_reader_tolerates_header_shorter_than_wal_header_size() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("short.wal");
// Simulates a kill mid-write_wal_header: only the magic made it out.
std::fs::write(&path, b"MWAL").unwrap();
let mut reader = WalReader::open(&path).unwrap();
let entries = reader.read_entries().unwrap();
assert!(
entries.is_empty(),
"a too-short WAL header must read back as empty, not error"
);
}
/// As above, but for the writer side: re-opening a WAL left too short
/// by a prior crash must re-initialize it with a fresh header instead
/// of failing `open_or_create`, and the WAL must be fully usable
/// afterward.
#[test]
fn test_wal_writer_reinitializes_header_shorter_than_wal_header_size() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("short.wal");
std::fs::write(&path, b"MW").unwrap();
let mut writer = WalWriter::open_or_create(&path).unwrap();
let alice = Uuid::new_v4();
let fact = make_fact(alice, ":name", Value::String("Alice".to_string()), 1);
writer
.append_entry(1, std::slice::from_ref(&fact), SyncMode::Full)
.unwrap();
drop(writer);
let mut reader = WalReader::open(&path).unwrap();
let entries = reader.read_entries().unwrap();
assert_eq!(entries.len(), 1, "re-initialized WAL must accept entries");
}
/// A completely empty (0-byte) WAL file -- the earliest possible point
/// in the crash window, right after `create_new` -- must be tolerated
/// the same way.
#[test]
fn test_wal_reader_tolerates_zero_byte_file() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("empty.wal");
std::fs::write(&path, []).unwrap();
let mut reader = WalReader::open(&path).unwrap();
let entries = reader.read_entries().unwrap();
assert!(entries.is_empty(), "a 0-byte WAL must read back as empty");
}
#[test]
fn test_wal_truncated_entry_stops_replay() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
let alice = Uuid::new_v4();
let fact = make_fact(alice, ":name", Value::String("Alice".to_string()), 1);
// Write a valid entry
let mut writer = WalWriter::open_or_create(&path).unwrap();
writer.append_entry(1, &[fact], SyncMode::Full).unwrap();
drop(writer);
// Append garbage bytes after the valid entry to simulate a partial second write
let mut file = OpenOptions::new().append(true).open(&path).unwrap();
file.write_all(&[0xFF, 0xFF, 0xFF, 0xFF, 0x01]).unwrap(); // bad checksum prefix
drop(file);
let mut reader = WalReader::open(&path).unwrap();
let entries = reader.read_entries().unwrap();
// Only the valid first entry should be returned
assert_eq!(entries.len(), 1);
assert_eq!(entries[0].tx_count, 1);
}
// ── #513: torn tail and failed appends ─────────────────────────────────
/// The bytes of a WAL holding entries `1..=n`.
fn wal_with_entries(path: &Path, n: u64) -> Vec<u8> {
let mut writer = WalWriter::open_or_create(path).unwrap();
for tx in 1..=n {
let fact = make_fact(Uuid::new_v4(), ":name", Value::Integer(tx as i64), tx);
writer.append_entry(tx, &[fact], SyncMode::Full).unwrap();
}
drop(writer);
std::fs::read(path).unwrap()
}
fn tx_counts(path: &Path) -> Vec<u64> {
let mut reader = WalReader::open(path).unwrap();
let entries = reader.read_entries().unwrap();
entries.iter().map(|e| e.tx_count).collect()
}
#[test]
fn test_wal_writer_cuts_off_torn_tail_before_appending() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
let two = wal_with_entries(&path, 2);
let one_len = {
let p = dir.path().join("one.wal");
wal_with_entries(&p, 1).len()
};
let second = two.len() - one_len;
for cut in [1, 4, 12, 20, second - 1] {
std::fs::write(&path, &two[..one_len + cut]).unwrap();
let mut writer = WalWriter::open_or_create(&path).unwrap();
assert_eq!(
std::fs::metadata(&path).unwrap().len(),
one_len as u64,
"the partial entry is cut off on open"
);
let fact = make_fact(Uuid::new_v4(), ":name", Value::Integer(7), 7);
writer.append_entry(7, &[fact], SyncMode::Full).unwrap();
drop(writer);
assert_eq!(tx_counts(&path), [1, 7], "the new entry is reachable");
}
}
#[test]
fn test_wal_writer_cuts_off_entry_with_bad_checksum() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
let mut bytes = wal_with_entries(&path, 3);
let one_len = {
let p = dir.path().join("one.wal");
wal_with_entries(&p, 1).len()
};
// Damage entry 2; entry 3 after it is unreachable and goes too.
bytes[one_len] ^= 0xFF;
std::fs::write(&path, &bytes).unwrap();
let writer = WalWriter::open_or_create(&path).unwrap();
drop(writer);
assert_eq!(std::fs::metadata(&path).unwrap().len(), one_len as u64);
assert_eq!(tx_counts(&path), [1]);
}
#[test]
fn test_wal_writer_keeps_an_intact_wal() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
let bytes = wal_with_entries(&path, 3);
let writer = WalWriter::open_or_create(&path).unwrap();
drop(writer);
assert!(std::fs::read(&path).unwrap() == bytes, "nothing to cut");
}
#[test]
fn test_wal_failed_append_refuses_later_appends_with_wal_007() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
let mut writer = WalWriter::open_or_create(&path).unwrap();
let fact = |tx: u64| make_fact(Uuid::new_v4(), ":name", Value::Integer(1), tx);
writer.append_entry(1, &[fact(1)], SyncMode::Full).unwrap();
fault::arm(fault::Fault::Torn(10), 0);
writer
.append_entry(2, &[fact(2)], SyncMode::Full)
.expect_err("the torn append fails");
assert_eq!(fault::disarm(), Some(Site::WalWrite));
let err: crate::error::MinigrafError = writer
.append_entry(3, &[fact(3)], SyncMode::Full)
.expect_err("later appends are refused")
.into();
assert_eq!(err.code(), "WAL-007");
drop(writer);
assert_eq!(tx_counts(&path), [1], "nothing after the torn entry");
// A new writer cuts off the partial entry and appends normally.
let mut writer = WalWriter::open_or_create(&path).unwrap();
writer.append_entry(4, &[fact(4)], SyncMode::Full).unwrap();
drop(writer);
assert_eq!(tx_counts(&path), [1, 4]);
}
/// A set's size bound and its keyword elements are checked (#316).
#[test]
fn check_fact_size_checks_sets() {
use crate::graph::types::ValueSet;
let code = |v: Value| {
check_fact_size(&make_fact(Uuid::new_v4(), ":s", v, 1))
.map_err(|e| crate::MinigrafError::from(e).code())
};
let set = |v: Vec<Value>| Value::Set(ValueSet::new(v).unwrap());
// A keyword element longer than an ident may be.
let long_kw = format!(":{}", "k".repeat(MAX_IDENT_BYTES));
assert_eq!(code(set(vec![Value::Keyword(long_kw)])), Err("WAL-003"));
// At the bound: one string element of n bytes counts n + 3.
let at = MAX_VALUE_BYTES - 3;
assert_eq!(code(set(vec![Value::String("s".repeat(at))])), Ok(()));
assert_eq!(
code(set(vec![Value::String("s".repeat(at + 1))])),
Err("WAL-003")
);
// Short keywords and other elements pass.
assert_eq!(
code(set(vec![Value::Keyword(":a".into()), Value::Integer(1)])),
Ok(())
);
}
#[test]
fn test_wal_rejected_entry_does_not_poison_the_writer() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
let mut writer = WalWriter::open_or_create(&path).unwrap();
let huge = make_fact(
Uuid::new_v4(),
":name",
Value::String("x".repeat(MAX_VALUE_BYTES + 1)),
1,
);
writer
.append_entry(1, &[huge], SyncMode::Full)
.expect_err("WAL-003, before anything is written");
let fact = make_fact(Uuid::new_v4(), ":name", Value::Integer(1), 2);
writer.append_entry(2, &[fact], SyncMode::Full).unwrap();
drop(writer);
assert_eq!(tx_counts(&path), [2]);
}
#[test]
fn test_wal_delete_file() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
WalWriter::open_or_create(&path).unwrap();
assert!(path.exists());
WalWriter::delete_file(&path).unwrap();
assert!(!path.exists());
}