Repository navigation
Expand file tree
/
Copy pathwal.rs
More file actions
541 lines (466 loc) · 19.1 KB
/
Copy pathwal.rs
File metadata and controls
541 lines (466 loc) · 19.1 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
//! 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 = 1
//! reserved: [u8; 24]
//!
//! 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::graph::types::Fact;
use crate::storage::packed_pages::MAX_FACT_BYTES;
use anyhow::{Result, bail};
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 = 1;
const WAL_HEADER_SIZE: usize = 32;
// ─── WAL Header ─────────────────────────────────────────────────────────────
fn write_wal_header(file: &mut File) -> 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());
// bytes 8..32 are reserved zeros
file.seek(SeekFrom::Start(0))?;
file.write_all(&buf)?;
file.sync_all()?;
Ok(())
}
fn validate_wal_header(file: &mut File) -> Result<()> {
let mut buf = [0u8; WAL_HEADER_SIZE];
file.seek(SeekFrom::Start(0))?;
file.read_exact(&mut buf)?;
if buf[0..4] != WAL_MAGIC {
bail!("Invalid WAL magic number: not a .wal file");
}
let version = u32::from_le_bytes([buf[4], buf[5], buf[6], buf[7]]);
if version != WAL_VERSION {
bail!(
"Unsupported WAL version: {} (expected {})",
version,
WAL_VERSION
);
}
Ok(())
}
// ─── Entry serialization ────────────────────────────────────────────────────
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 {
let fact_bytes = postcard::to_allocvec(fact)?;
if fact_bytes.len() > MAX_FACT_BYTES {
bail!(
"Fact serialised size {} bytes exceeds maximum {} bytes. \
Store large payloads externally and reference them with a \
Value::String URL/path or Value::Ref entity ID.",
fact_bytes.len(),
MAX_FACT_BYTES
);
}
let fact_len = u32::try_from(fact_bytes.len()).map_err(|_| {
anyhow::anyhow!(
"fact serialised size {} exceeds u32 range",
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.
pub struct WalWriter {
file: File,
}
impl WalWriter {
/// Open an existing WAL or create a new one.
///
/// If creating, writes the WAL header.
/// If opening, validates the header and seeks to the end for appending.
pub fn open_or_create(path: &Path) -> 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) => {
write_wal_header(&mut file)?;
file.seek(SeekFrom::End(0))?;
return Ok(WalWriter { file });
}
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)?;
validate_wal_header(&mut file)?;
file.seek(SeekFrom::End(0))?;
Ok(WalWriter { file })
}
/// Serialize `facts` as a WAL entry and append it to the file, then fsync.
///
/// The entry is written atomically from the caller's perspective:
/// a partial write produces a bad CRC32, which the reader discards.
pub fn append_entry(&mut self, tx_count: u64, facts: &[Fact]) -> Result<()> {
let entry_bytes = serialize_entry(tx_count, facts)?;
self.file.write_all(&entry_bytes)?;
self.file.sync_all()?;
Ok(())
}
/// Delete the WAL file at `path`. Called after a successful checkpoint.
///
/// 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 {
match std::fs::remove_file(path) {
Ok(()) => return Ok(()),
Err(e) => {
last_err = Some(e);
if i.saturating_add(1) < retries {
std::thread::sleep(std::time::Duration::from_millis(50));
}
}
}
}
Err(anyhow::anyhow!(
"failed to delete WAL file {}: {}",
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,
}
impl WalReader {
/// Open the WAL at `path` for reading.
pub fn open(path: &Path) -> Result<Self> {
let mut file = File::open(path)?;
validate_wal_header(&mut file)?;
Ok(WalReader { file })
}
/// 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>> {
self.file.seek(SeekFrom::Start(WAL_HEADER_SIZE as u64))?;
let mut entries = Vec::new();
loop {
// Read checksum (4 bytes); EOF here means no more entries
let mut csum_buf = [0u8; 4];
match self.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 self.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 self.file.read_exact(&mut num_facts_buf).is_err() {
break; // truncated
}
let num_facts = usize::try_from(u64::from_le_bytes(num_facts_buf))
.map_err(|_| anyhow::anyhow!("WAL num_facts exceeds platform usize"))?;
// Sanity cap: no legitimate entry has more than 1M facts
const MAX_FACTS_PER_ENTRY: usize = 1_000_000;
if num_facts > MAX_FACTS_PER_ENTRY {
break; // treat as corrupt entry
}
// 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 self.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 self.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 });
}
Ok(entries)
}
}
// ─── 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)).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_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).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,
)],
)
.unwrap();
writer
.append_entry(
2,
&[make_fact(bob, ":name", Value::String("Bob".to_string()), 2)],
)
.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,
)],
)
.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)],
)
.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");
}
#[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]).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);
}
#[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());
}
#[test]
fn test_wal_fact_size_limit() {
use crate::graph::types::{Fact, Value};
use uuid::Uuid;
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("test.wal");
let mut writer = WalWriter::open_or_create(&path).unwrap();
let entity = Uuid::new_v4();
let fact = Fact::new(
entity,
":test".to_string(),
Value::String("x".to_string()),
1,
);
// Write an entry with one fact
writer.append_entry(1, &[fact]).unwrap();
writer.file.sync_all().unwrap();
// Manually corrupt the WAL to have a fact larger than MAX_FACT_SIZE
let mut file = std::fs::OpenOptions::new().write(true).open(&path).unwrap();
file.seek(std::io::SeekFrom::End(-20)).unwrap();
// Overwrite the fact length to be huge
let huge_len: u32 = (10 * 1024 * 1024 + 1) as u32; // Just over MAX_FACT_SIZE
file.write_all(&huge_len.to_le_bytes()).unwrap();
drop(file);
// Try to read - should fail gracefully
let mut reader = WalReader::open(&path).unwrap();
let result = reader.read_entries();
assert!(
result.is_err() || result.unwrap().is_empty(),
"Should fail or return empty on corrupted large fact"
);
}
}