diff options
Diffstat (limited to 'src/wal.rs')
| -rw-r--r-- | src/wal.rs | 354 |
1 files changed, 354 insertions, 0 deletions
diff --git a/src/wal.rs b/src/wal.rs new file mode 100644 index 0000000..05ffd01 --- /dev/null +++ b/src/wal.rs @@ -0,0 +1,354 @@ +use std::collections::BinaryHeap; + +#[repr(u8)] +enum WALRingType { + #[allow(dead_code)] + Null = 0x0, + Full, + First, + Middle, + Last +} + +#[repr(packed)] +struct WALRingBlob { + crc32: u32, + rsize: u32, + rtype: WALRingType, + // payload follows +} + +pub type WALBytes = Box<[u8]>; +pub type WALFileId = u64; +pub type WALPos = u64; + +#[derive(Eq, PartialEq, Copy, Clone, Debug)] +pub struct WALRingId { + start: WALPos, + end: WALPos +} + +impl Ord for WALRingId { + fn cmp(&self, other: &WALRingId) -> std::cmp::Ordering { + other.start.cmp(&self.start).then_with(|| other.end.cmp(&self.end)) + } +} + +impl PartialOrd for WALRingId { + fn partial_cmp(&self, other: &WALRingId) -> Option<std::cmp::Ordering> { + Some(self.cmp(other)) + } +} + +/// the state for a WAL writer +struct WALState { + /// the first file id of WAL + first_fid: WALFileId, + /// the next position for a record, addressed in the entire WAL space + next: WALPos, + /// number of bits for a file + file_nbit: u64, +} + +pub trait WALFile { + /// Initialize the file space in [offset, offset + length) to zero. + fn allocate(&self, offset: WALPos, length: usize) -> Result<(), ()>; + /// Truncate a file to a specified length. + fn truncate(&self, length: usize) -> Result<(), ()>; + /// Write data with offset. + fn write(&self, offset: WALPos, data: WALBytes); + /// Read data with offset. + fn read(&self, offset: WALPos, length: usize) -> WALBytes; +} + +pub trait WALStore { + /// Open a file given the filename, create the file if not exists when `touch` is `true`. + fn open_file(&self, filename: &str, touch: bool) -> Option<Box<dyn WALFile>>; + /// Unlink a file given the filename. + fn remove_file(&self, filename: &str) -> Result<(), ()>; + /// Enumerate all WAL files. + fn enumerate_files(&self) -> Box<[String]>; + /// Apply (redo) the payload during recovery. + fn apply_payload(&self, payload: WALBytes); +} + +/// The middle layer that manages WAL file handles and invokes public trait functions to actually +/// manipulate files and their contents. +struct WALFilePool<F: WALStore> { + store: F, + handles: lru::LruCache<WALFileId, Box<dyn WALFile>>, + file_nbit: u64, + file_size: u64, + block_nbit: u64, +} + +impl<F: WALStore> WALFilePool<F> { + fn new(store: F, file_nbit: u8, block_nbit: u8, cache_size: usize) -> Self { + let file_nbit = file_nbit as u64; + let block_nbit = block_nbit as u64; + WALFilePool { + store, + handles: lru::LruCache::new(cache_size), + file_nbit, + file_size: 1 << (file_nbit as u64), + block_nbit, + } + } + + fn get_fname(fid: WALFileId) -> String { + format!("{:08x}.log", fid) + } + + fn get_file(&mut self, fid: u64, touch: bool) -> &'static dyn WALFile { + let h = match self.handles.get(&fid) { + Some(h) => &**h, + None => { + self.handles.put(fid, self.store.open_file(&Self::get_fname(fid), touch).unwrap()); + &**self.handles.get(&fid).unwrap() + } + }; + unsafe {&*(h as *const dyn WALFile)} + } + + fn get_fid(&mut self, fname: &str) -> WALFileId { + scan_fmt!(fname, "{x}.log", [hex WALFileId]).unwrap() + } + + // TODO: evict stale handles + fn write(&mut self, writes: Vec<(WALPos, WALBytes)>) { + // pre-allocate the file space + let mut fid = writes[0].0 >> self.file_nbit; + let mut alloc_start = writes[0].0 & (self.file_size - 1); + let mut alloc_end = alloc_start + writes[0].1.len() as u64; + let mut h = self.get_file(fid, true); + for (off, w) in &writes[1..] { + let next_fid = off >> self.file_nbit; + if next_fid != fid { + h.allocate(alloc_start, (alloc_end - alloc_start) as usize).unwrap(); + h = self.get_file(next_fid, true); + alloc_start = 0; + alloc_end = alloc_start + w.len() as u64; + fid = next_fid; + } else { + alloc_end += w.len() as u64; + } + } + h.allocate(alloc_start, (alloc_end - alloc_start) as usize).unwrap(); + for (off, w) in writes.into_iter() { + self.get_file(off >> self.file_nbit, true).write(off & (self.file_size - 1), w); + } + } + + fn remove_file(&self, fid: u64) -> Result<(), ()> { + self.store.remove_file(&Self::get_fname(fid)) + } + + fn reset(&mut self) { self.handles.clear() } +} + +pub struct WALWriter<F: WALStore> { + state: WALState, + file_pool: WALFilePool<F>, + block_buffer: WALBytes, + block_size: u32, + next_complete: WALPos, + io_complete: BinaryHeap<WALRingId> +} + +impl<F: WALStore> WALWriter<F> { + fn new(state: WALState, file_pool: WALFilePool<F>) -> Self { + let mut b = Vec::new(); + let block_size = 1 << file_pool.block_nbit as u32; + //let block_nbit = state.block_nbit; + //let block_size = 1 << (block_nbit as u32); + //let file_nbit = state.file_nbit; + //let file_size = 1 << (file_nbit as u64); + b.resize(block_size as usize, 0); + WALWriter{ + state, + file_pool, + block_buffer: b.into_boxed_slice(), + block_size, + next_complete: 0, + io_complete: BinaryHeap::new(), + } + } + + /// Submit a sequence of records to WAL; WALStore/WALFile callbacks are invoked before the + /// function returns. The caller then has the knowledge of WAL writes so it should defer + /// actual data writes after WAL writes. + pub fn grow<T: AsRef<[WALBytes]>>(&mut self, records: T) -> Box<[WALRingId]> { + let mut res = Vec::new(); + let mut writes = Vec::new(); + let msize = std::mem::size_of::<WALRingBlob>() as u32; + // the global offest of the begining of the block + // the start of the unwritten data + let mut bbuff_start = self.state.next as u32 & (self.block_size - 1); + // the end of the unwritten data + let mut bbuff_cur = bbuff_start; + + for _rec in records.as_ref() { + let mut rec = &_rec[..]; + let mut rsize = rec.len() as u32; + let mut started = false; + while rsize > 0 { + let remain = self.block_size - bbuff_cur; + if remain > msize { + let d = remain - msize; + let ring_start = self.state.next + (bbuff_cur - bbuff_start) as u64; + let blob = unsafe {std::mem::transmute::<*mut u8, &mut WALRingBlob>( + (&mut self.block_buffer[bbuff_cur as usize..]).as_mut_ptr())}; + bbuff_cur += msize; + if d >= rsize { + // the remaining rec fits in the block + let payload = rec; + blob.crc32 = crc::crc32::checksum_ieee(payload); + blob.rsize = rsize; + blob.rtype = if started {WALRingType::Last} else {WALRingType::Full}; + &mut self.block_buffer[ + bbuff_cur as usize.. + bbuff_cur as usize + payload.len()].copy_from_slice(payload); + bbuff_cur += rsize; + rsize = 0; + } else { + // the remaining block can only accommodate partial rec + let payload = &rec[..d as usize]; + blob.crc32 = crc::crc32::checksum_ieee(payload); + blob.rsize = d; + blob.rtype = if started {WALRingType::Middle} else { + started = true; + WALRingType::First + }; + &mut self.block_buffer[ + bbuff_cur as usize.. + bbuff_cur as usize + payload.len()].copy_from_slice(payload); + bbuff_cur += d; + rsize -= d; + rec = &rec[d as usize..]; + } + let ring_end = self.state.next + (bbuff_cur - bbuff_start) as u64; + res.push(WALRingId{start: ring_start, end: ring_end}); + } else { + // add padding space by moving the point to the end of the block + bbuff_cur = self.block_size; + } + if bbuff_cur == self.block_size { + writes.push((self.state.next, + self.block_buffer[bbuff_start as usize..] + .to_vec().into_boxed_slice())); + self.state.next += (self.block_size - bbuff_start) as u64; + bbuff_start = 0; + bbuff_cur = 0; + } + } + } + if bbuff_cur > bbuff_start { + writes.push((self.state.next, + self.block_buffer[bbuff_start as usize..bbuff_cur as usize] + .to_vec().into_boxed_slice())); + self.state.next += (bbuff_cur - bbuff_start) as u64; + } + self.file_pool.write(writes); + res.into_boxed_slice() + } + + /// Inform the WALWriter that data writes (specified by a slice of (offset, length) tuples) are + /// complete so that it could automatically remove obsolete WAL files. + pub fn peel<T: AsRef<[WALRingId]>>(&mut self, records: T) { + let msize = std::mem::size_of::<WALRingBlob>() as u64; + let block_size = self.block_size as u64; + for rec in records.as_ref() { + self.io_complete.push(*rec) + } + let orig_fid = self.state.first_fid; + while let Some(s) = self.io_complete.peek().and_then(|&e| Some(e.start)) { + if s != self.next_complete { + break + } + let mut m = self.io_complete.pop().unwrap(); + let block_remain = block_size - (m.end & (block_size - 1)); + if block_remain <= msize as u64 { + m.end += block_remain + } + self.next_complete = m.end + } + let next_fid = self.next_complete >> self.state.file_nbit; + for fid in orig_fid..next_fid { + self.file_pool.remove_file(fid).unwrap(); + } + self.state.first_fid = next_fid; + } +} + +pub struct WALLoader<F: WALStore> { + file_pool: WALFilePool<F>, +} + +impl<F: WALStore> WALLoader<F> { + pub fn new(store: F, file_nbit: u8, block_nbit: u8, cache_size: usize) -> Self { + let file_pool = WALFilePool::new(store, file_nbit, block_nbit, cache_size); + WALLoader{ file_pool } + } + + pub fn recover(mut self) -> WALWriter<F> { + let block_size = 1 << self.file_pool.block_nbit; + let msize = std::mem::size_of::<WALRingBlob>() as u32; + let mut logfiles = self.file_pool.store.enumerate_files(); + // TODO: use regex to filter out invalid files + // TODO: check for missing logfiles + logfiles.sort(); + let mut chunks = None; + for fname in logfiles.iter() { + let fid = self.file_pool.get_fid(fname); + let f = self.file_pool.get_file(fid, false); + let mut off = 0; + while block_size - (off & (block_size - 1)) > msize as u64 { + let header_raw = f.read(off, msize as usize); + off += msize as u64; + let header = unsafe { + std::mem::transmute::<*const u8, &WALRingBlob>(header_raw.as_ptr())}; + let rsize = header.rsize; + match header.rtype { + WALRingType::Full => { + assert!(chunks.is_none()); + let payload = f.read(off, rsize as usize); + off += rsize as u64; + self.file_pool.store.apply_payload(payload); + }, + WALRingType::First => { + assert!(chunks.is_none()); + chunks = Some(vec![f.read(off, rsize as usize)]); + off += rsize as u64; + }, + WALRingType::Middle => { + chunks.as_mut().unwrap().push(f.read(off, rsize as usize)); + off += rsize as u64; + }, + WALRingType::Last => { + chunks.as_mut().unwrap().push(f.read(off, rsize as usize)); + off += rsize as u64; + + let _chunks = chunks.take().unwrap(); + let mut payload = Vec::new(); + payload.resize(_chunks.iter().fold(0, |acc, v| acc + v.len()), 0); + let mut ps = &mut payload[..]; + for c in _chunks { + ps[..c.len()].copy_from_slice(&*c); + ps = &mut ps[c.len()..]; + } + self.file_pool.store.apply_payload(payload.into_boxed_slice()); + }, + WALRingType::Null => break, + } + } + f.truncate(0).unwrap(); + self.file_pool.remove_file(fid).unwrap(); + } + self.file_pool.reset(); + WALWriter::new(WALState { + first_fid: 0, + next: 0, + file_nbit: self.file_pool.file_nbit, + }, self.file_pool) + } +} |