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
/// This module implements the "container" file format that `measureme` uses for
/// storing things on disk. The format supports storing three independent
/// streams of data: one for events, one for string data, and one for string
/// index data (in theory it could support an arbitrary number of separate
/// streams but three is all we need). The data of each stream is split into
/// "pages", where each page has a small header designating what kind of
/// data it is (i.e. event, string data, or string index), and the length of
/// the page.
///
/// Pages of different kinds can be arbitrarily interleaved. The headers allow
/// for reconstructing each of the streams later on. An example file might thus
/// look like this:
///
/// ```ignore
/// | file header | page (events) | page (string data) | page (events) | page (string index) |
/// ```
///
/// The exact encoding of a page is:
///
/// | byte slice | contents |
/// |-------------------------|-----------------------------------------|
/// | &[0 .. 1] | page tag |
/// | &[1 .. 5] | page size as little endian u32 |
/// | &[5 .. (5 + page_size)] | page contents (exactly page_size bytes) |
///
/// A page is immediately followed by the next page, without any padding.
use parking_lot::Mutex;
use rustc_hash::FxHashMap;
use std::cmp::min;
use std::convert::TryInto;
use std::error::Error;
use std::fmt::Debug;
use std::fs;
use std::io::Write;
use std::sync::Arc;
const MAX_PAGE_SIZE: usize = 256 * 1024;
/// The number of bytes we consider enough to warrant their own page when
/// deciding whether to flush a partially full buffer. Actual pages may need
/// to be smaller, e.g. when writing the tail of the data stream.
const MIN_PAGE_SIZE: usize = MAX_PAGE_SIZE / 2;
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
#[repr(u8)]
pub enum PageTag {
Events = 0,
StringData = 1,
StringIndex = 2,
}
impl std::convert::TryFrom<u8> for PageTag {
type Error = String;
fn try_from(value: u8) -> Result<Self, Self::Error> {
match value {
0 => Ok(PageTag::Events),
1 => Ok(PageTag::StringData),
2 => Ok(PageTag::StringIndex),
_ => Err(format!("Could not convert byte `{}` to PageTag.", value)),
}
}
}
/// An address within a data stream. Each data stream has its own address space,
/// i.e. the first piece of data written to the events stream will have
/// `Addr(0)` and the first piece of data written to the string data stream
/// will *also* have `Addr(0)`.
//
// TODO: Evaluate if it makes sense to add a type tag to `Addr` in order to
// prevent accidental use of `Addr` values with the wrong address space.
#[derive(Clone, Copy, Eq, PartialEq, Debug)]
pub struct Addr(pub u64);
impl Addr {
pub fn as_usize(self) -> usize {
self.0 as usize
}
}
#[derive(Debug)]
pub struct SerializationSink {
shared_state: SharedState,
data: Mutex<SerializationSinkInner>,
page_tag: PageTag,
}
pub struct SerializationSinkBuilder(SharedState);
impl SerializationSinkBuilder {
pub fn new_from_file(file: fs::File) -> Result<Self, Box<dyn Error + Send + Sync>> {
Ok(Self(SharedState(Arc::new(Mutex::new(
BackingStorage::File(file),
)))))
}
pub fn new_in_memory() -> SerializationSinkBuilder {
Self(SharedState(Arc::new(Mutex::new(BackingStorage::Memory(
Vec::new(),
)))))
}
pub fn new_sink(&self, page_tag: PageTag) -> SerializationSink {
SerializationSink {
data: Mutex::new(SerializationSinkInner {
buffer: Vec::with_capacity(MAX_PAGE_SIZE),
addr: 0,
}),
shared_state: self.0.clone(),
page_tag,
}
}
}
/// The `BackingStorage` is what the data gets written to. Usually that is a
/// file but for testing purposes it can also be an in-memory vec of bytes.
#[derive(Debug)]
enum BackingStorage {
File(fs::File),
Memory(Vec<u8>),
}
impl Write for BackingStorage {
#[inline]
fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
match *self {
BackingStorage::File(ref mut file) => file.write(buf),
BackingStorage::Memory(ref mut vec) => vec.write(buf),
}
}
fn flush(&mut self) -> std::io::Result<()> {
match *self {
BackingStorage::File(ref mut file) => file.flush(),
BackingStorage::Memory(_) => {
// Nothing to do
Ok(())
}
}
}
}
/// This struct allows to treat `SerializationSink` as `std::io::Write`.
pub struct StdWriteAdapter<'a>(&'a SerializationSink);
impl<'a> Write for StdWriteAdapter<'a> {
fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
self.0.write_bytes_atomic(buf);
Ok(buf.len())
}
fn flush(&mut self) -> std::io::Result<()> {
let mut data = self.0.data.lock();
let SerializationSinkInner {
ref mut buffer,
addr: _,
} = *data;
// First flush the local buffer.
self.0.flush(buffer);
// Then flush the backing store.
self.0.shared_state.0.lock().flush()?;
Ok(())
}
}
#[derive(Debug)]
struct SerializationSinkInner {
buffer: Vec<u8>,
addr: u64,
}
/// This state is shared between all `SerializationSink`s writing to the same
/// backing storage (e.g. the same file).
#[derive(Clone, Debug)]
struct SharedState(Arc<Mutex<BackingStorage>>);
impl SharedState {
/// Copies out the contents of all pages with the given tag and
/// concatenates them into a single byte vec. This method is only meant to
/// be used for testing and will panic if the underlying backing storage is
/// a file instead of in memory.
fn copy_bytes_with_page_tag(&self, page_tag: PageTag) -> Vec<u8> {
let data = self.0.lock();
let data = match *data {
BackingStorage::File(_) => panic!(),
BackingStorage::Memory(ref data) => data,
};
split_streams(data).remove(&page_tag).unwrap_or(Vec::new())
}
}
/// This function reconstructs the individual data streams from their paged
/// version.
///
/// For example, if `E` denotes the page header of an events page, `S` denotes
/// the header of a string data page, and lower case letters denote page
/// contents then a paged stream could look like:
///
/// ```ignore
/// s = Eabcd_Sopq_Eef_Eghi_Srst
/// ```
///
/// and `split_streams` would result in the following set of streams:
///
/// ```ignore
/// split_streams(s) = {
/// events: [abcdefghi],
/// string_data: [opqrst],
/// }
/// ```
pub fn split_streams(paged_data: &[u8]) -> FxHashMap<PageTag, Vec<u8>> {
let mut result: FxHashMap<PageTag, Vec<u8>> = FxHashMap::default();
let mut pos = 0;
while pos < paged_data.len() {
let tag = TryInto::try_into(paged_data[pos]).unwrap();
let page_size =
u32::from_le_bytes(paged_data[pos + 1..pos + 5].try_into().unwrap()) as usize;
assert!(page_size > 0);
result
.entry(tag)
.or_default()
.extend_from_slice(&paged_data[pos + 5..pos + 5 + page_size]);
pos += page_size + 5;
}
result
}
impl SerializationSink {
/// Writes `bytes` as a single page to the shared backing storage. The
/// method will first write the page header (consisting of the page tag and
/// the number of bytes in the page) and then the page contents
/// (i.e. `bytes`).
fn write_page(&self, bytes: &[u8]) {
if bytes.len() > 0 {
// We explicitly don't assert `bytes.len() >= MIN_PAGE_SIZE` because
// `MIN_PAGE_SIZE` is just a recommendation and the last page will
// often be smaller than that.
assert!(bytes.len() <= MAX_PAGE_SIZE);
let mut file = self.shared_state.0.lock();
file.write_all(&[self.page_tag as u8]).unwrap();
let page_size: [u8; 4] = (bytes.len() as u32).to_le_bytes();
file.write_all(&page_size).unwrap();
file.write_all(&bytes[..]).unwrap();
}
}
/// Flushes `buffer` by writing its contents as a new page to the backing
/// storage and then clearing it.
fn flush(&self, buffer: &mut Vec<u8>) {
self.write_page(&buffer[..]);
buffer.clear();
}
/// Creates a copy of all data written so far. This method is meant to be
/// used for writing unit tests. It will panic if the underlying
/// `BackingStorage` is a file.
pub fn into_bytes(mut self) -> Vec<u8> {
// Swap out the contains of `self` with something that can safely be
// dropped without side effects.
let mut data = Mutex::new(SerializationSinkInner {
buffer: Vec::new(),
addr: 0,
});
std::mem::swap(&mut self.data, &mut data);
// Extract the data from the mutex.
let SerializationSinkInner {
ref mut buffer,
addr: _,
} = data.into_inner();
// Make sure we write the current contents of the buffer to the
// backing storage before proceeding.
self.flush(buffer);
self.shared_state.copy_bytes_with_page_tag(self.page_tag)
}
/// Atomically writes `num_bytes` of data to this `SerializationSink`.
/// Atomic means the data is guaranteed to be written as a contiguous range
/// of bytes.
///
/// The buffer provided to the `write` callback is guaranteed to be of size
/// `num_bytes` and `write` is supposed to completely fill it with the data
/// to be written.
///
/// The return value is the address of the data written and can be used to
/// refer to the data later on.
pub fn write_atomic<W>(&self, num_bytes: usize, write: W) -> Addr
where
W: FnOnce(&mut [u8]),
{
if num_bytes > MAX_PAGE_SIZE {
let mut bytes = vec![0u8; num_bytes];
write(&mut bytes[..]);
return self.write_bytes_atomic(&bytes[..]);
}
let mut data = self.data.lock();
let SerializationSinkInner {
ref mut buffer,
ref mut addr,
} = *data;
if buffer.len() + num_bytes > MAX_PAGE_SIZE {
self.flush(buffer);
assert!(buffer.is_empty());
}
let curr_addr = *addr;
let buf_start = buffer.len();
let buf_end = buf_start + num_bytes;
buffer.resize(buf_end, 0u8);
write(&mut buffer[buf_start..buf_end]);
*addr += num_bytes as u64;
Addr(curr_addr)
}
/// Atomically writes the data in `bytes` to this `SerializationSink`.
/// Atomic means the data is guaranteed to be written as a contiguous range
/// of bytes.
///
/// This method may perform better than `write_atomic` because it may be
/// able to skip the sink's internal buffer. Use this method if the data to
/// be written is already available as a `&[u8]`.
///
/// The return value is the address of the data written and can be used to
/// refer to the data later on.
pub fn write_bytes_atomic(&self, bytes: &[u8]) -> Addr {
// For "small" data we go to the buffered version immediately.
if bytes.len() <= 128 {
return self.write_atomic(bytes.len(), |sink| {
sink.copy_from_slice(bytes);
});
}
let mut data = self.data.lock();
let SerializationSinkInner {
ref mut buffer,
ref mut addr,
} = *data;
let curr_addr = Addr(*addr);
*addr += bytes.len() as u64;
let mut bytes_left = bytes;
// Do we have too little data in the buffer? If so, fill up the buffer
// to the minimum page size.
if buffer.len() < MIN_PAGE_SIZE {
let num_bytes_to_take = min(MIN_PAGE_SIZE - buffer.len(), bytes_left.len());
buffer.extend_from_slice(&bytes_left[..num_bytes_to_take]);
bytes_left = &bytes_left[num_bytes_to_take..];
}
if bytes_left.is_empty() {
return curr_addr;
}
// Make sure we flush the buffer before writing out any other pages.
self.flush(buffer);
for chunk in bytes_left.chunks(MAX_PAGE_SIZE) {
if chunk.len() == MAX_PAGE_SIZE {
// This chunk has the maximum size. It might or might not be the
// last one. In either case we want to write it to disk
// immediately because there is no reason to copy it to the
// buffer first.
self.write_page(chunk);
} else {
// This chunk is less than the chunk size that we requested, so
// it must be the last one. If it is big enough to warrant its
// own page, we write it to disk immediately. Otherwise, we copy
// it to the buffer.
if chunk.len() >= MIN_PAGE_SIZE {
self.write_page(chunk);
} else {
debug_assert!(buffer.is_empty());
buffer.extend_from_slice(chunk);
}
}
}
curr_addr
}
pub fn as_std_write<'a>(&'a self) -> impl Write + 'a {
StdWriteAdapter(self)
}
}
impl Drop for SerializationSink {
fn drop(&mut self) {
let mut data = self.data.lock();
let SerializationSinkInner {
ref mut buffer,
addr: _,
} = *data;
self.flush(buffer);
}
}
#[cfg(test)]
mod tests {
use super::*;
// This function writes `chunk_count` byte-slices of size `chunk_size` to
// three `SerializationSinks` that all map to the same underlying stream,
// so we get interleaved pages with different tags.
// It then extracts the data out again and asserts that it is the same as
// has been written.
fn test_roundtrip<W>(chunk_size: usize, chunk_count: usize, write: W)
where
W: Fn(&SerializationSink, &[u8]) -> Addr,
{
let sink_builder = SerializationSinkBuilder::new_in_memory();
let tags = [PageTag::Events, PageTag::StringData, PageTag::StringIndex];
let expected_chunk: Vec<u8> = (0..chunk_size).map(|x| (x % 239) as u8).collect();
{
let sinks: Vec<SerializationSink> =
tags.iter().map(|&tag| sink_builder.new_sink(tag)).collect();
for chunk_index in 0..chunk_count {
let expected_addr = Addr((chunk_index * chunk_size) as u64);
for sink in sinks.iter() {
assert_eq!(write(sink, &expected_chunk[..]), expected_addr);
}
}
}
let streams: Vec<Vec<u8>> = tags
.iter()
.map(|&tag| sink_builder.0.copy_bytes_with_page_tag(tag))
.collect();
for stream in streams {
for chunk in stream.chunks(chunk_size) {
assert_eq!(chunk, expected_chunk);
}
}
}
fn write_closure(sink: &SerializationSink, bytes: &[u8]) -> Addr {
sink.write_atomic(bytes.len(), |dest| dest.copy_from_slice(bytes))
}
fn write_slice(sink: &SerializationSink, bytes: &[u8]) -> Addr {
sink.write_bytes_atomic(bytes)
}
// Creates two roundtrip tests, one using `SerializationSink::write_atomic`
// and one using `SerializationSink::write_bytes_atomic`.
macro_rules! mk_roundtrip_test {
($name:ident, $chunk_size:expr, $chunk_count:expr) => {
mod $name {
use super::*;
#[test]
fn write_atomic() {
test_roundtrip($chunk_size, $chunk_count, write_closure);
}
#[test]
fn write_bytes_atomic() {
test_roundtrip($chunk_size, $chunk_count, write_slice);
}
}
};
}
mk_roundtrip_test!(small_data, 10, (90 * MAX_PAGE_SIZE) / 100);
mk_roundtrip_test!(huge_data, MAX_PAGE_SIZE * 10, 5);
mk_roundtrip_test!(exactly_max_page_size, MAX_PAGE_SIZE, 10);
mk_roundtrip_test!(max_page_size_plus_one, MAX_PAGE_SIZE + 1, 10);
mk_roundtrip_test!(max_page_size_minus_one, MAX_PAGE_SIZE - 1, 10);
mk_roundtrip_test!(exactly_min_page_size, MIN_PAGE_SIZE, 10);
mk_roundtrip_test!(min_page_size_plus_one, MIN_PAGE_SIZE + 1, 10);
mk_roundtrip_test!(min_page_size_minus_one, MIN_PAGE_SIZE - 1, 10);
}