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//! Simple crate that allows easy usage of rotating logfiles by faking being a
//! single [`std::io::Write`] implementor
//!
//! # Alright, sure, but what's a rotating logfile?
//!
//! Well, imagine we are logging *a lot*, and after a while we use up all our disk space with logs.
//! We don't want this, nobody wants this, so how do we solve it?
//!
//! We'll introduce the concept of changing what file we log to periodically, or in other words, we'll
//! *rotate* our log files so that we don't generate too much stored logging.
//!
//! One of the concepts that is involved in rotation is a limit to how many log files can exist at once.
//!
//! # Examples
//!
//! To demostrate what was said above, here's to create a file which rotates every day, storing up to a week of logs
//! in `/logs`
//!
//! ```rust
//! # use std::{time::Duration, num::NonZeroUsize};
//! # use file_rotator::{RotationPeriod, RotatingFile, Compression};
//! RotatingFile::new(
//! "loggylog",
//! "/logs",
//! RotationPeriod::Interval(Duration::from_secs(60 * 60 * 24)),
//! NonZeroUsize::new(7).unwrap(),
//! Compression::None,
//! );
//! ```
#![warn(
missing_docs,
missing_debug_implementations,
missing_copy_implementations
)]
use std::borrow::Cow;
use std::fs;
use std::io::{self, prelude::*};
use std::num::NonZeroUsize;
use std::path::{Path, PathBuf};
use std::time::Duration;
/// A specifier for how often we should rotate files
#[derive(Clone, Copy, Debug, Ord, PartialOrd, Eq, PartialEq)]
#[non_exhaustive]
pub enum RotationPeriod {
/// Rotate every N line terminator bytes (0x0a, b'\n')
Lines(usize),
/// Rotate every N bytes successfully written
///
/// This does not count bytes that are not written to the underlying file
/// (when the given buffer's len does not match with the return value of
/// [`io::Write::write`])
///
/// [`io::Write::write`]: https://doc.rust-lang.org/std/io/trait.Write.html#tymethod.write
Bytes(usize),
/// Rotate every time N amount of time passes
///
/// This is calculated on every write and is based on comparing two [`Instant::now`] return values
///
/// [`Instant::now`]: https://doc.rust-lang.org/std/time/struct.Instant.html#method.now
Interval(Duration),
/// Rotate only via [`RotatingFile::rotate`]
///
/// [`RotatingFile::rotate']: struct.RotatingFile.html#method.rotate
Manual,
}
mod rotation_tracker;
use rotation_tracker::RotationTracker;
/// As per the name, a rotating file
///
/// Handles being a fake file which will automagicaly rotate as bytes are written into it
#[derive(Debug)]
pub struct RotatingFile {
name: Cow<'static, str>,
directory: PathBuf,
rotation_tracker: RotationTracker,
max_index: usize,
compression: Compression,
current_file: Option<fs::File>,
}
/// What compression algorithm should be used?
///
/// The current log file (`NAME.0.log`) is always written uncompressed; once its time to rotate
/// out, compression will be applied. Depending on compression type, an extra extension might be
/// added.
#[derive(Clone, Copy, Debug)]
pub enum Compression {
/// No compression, just bytes to disk.
None,
/// Zstd compression.
Zstd {
/// What level of compression should be used? As per the zstd crate's docs, zero means default.
level: i32,
},
}
impl RotatingFile {
/// Create a new rotating file with the given base name, in the given directory, rotating every
/// given period and with a max of a given number of files
pub fn new<Name, Directory>(
name: Name,
directory: Directory,
rotate_every: RotationPeriod,
max_files: NonZeroUsize,
compression: Compression,
) -> Self
where
Name: Into<Cow<'static, str>>,
Directory: Into<PathBuf>,
{
Self {
name: name.into(),
directory: directory.into(),
rotation_tracker: RotationTracker::from(rotate_every),
max_index: max_files.get() - 1,
compression,
current_file: None,
}
}
fn should_rotate(&self) -> bool {
// If we have no current file, it's probably best if we make one :p
self.current_file.is_none() || self.rotation_tracker.should_rotate()
}
// Paths are split into three parts: NAME.INDEX.EXTENSION
// NAME is user-defined and unimportant to us, while EXTENSION must be either log or log.zstd
fn logfile_index<P: AsRef<Path>>(&self, path: P) -> Option<usize> {
let mut parts = path.as_ref().file_name()?.to_str()?.split('.');
match parts.next_back() {
Some("zstd") => {
if parts.next_back() != Some("log") {
return None;
}
}
Some("log") => {}
Some(..) | None => return None,
}
parts.next_back()?.parse().ok()
}
// Increment a log file's index component by one by moving it, compressing if necessary
fn increment_index(&self, index: usize) -> io::Result<()> {
let path = self.make_filepath(index);
let dst = self.make_filepath(index + 1);
debug_assert!(!dst.exists());
// If we're rotating out the current log file, we must compress it. Otherwise, everything's
// already compressed and we can just rotate
match self.compression {
Compression::Zstd { level } if index == 0 => {
zstd::stream::copy_encode(fs::File::open(&path)?, fs::File::create(dst)?, level)?;
fs::remove_file(&path)?;
Ok(())
}
Compression::None | Compression::Zstd { .. } => fs::rename(path, dst),
}
}
fn make_filepath(&self, index: usize) -> PathBuf {
self.directory.join(format!(
"{}.{}.{}",
self.name,
index,
match self.compression {
Compression::Zstd { .. } if index != 0 => "log.zstd",
Compression::None | Compression::Zstd { .. } => "log",
}
))
}
fn create_file(&self) -> io::Result<fs::File> {
// Let's survey the directory and find out what's the biggest index in there
let max_found_index = itertools::process_results(fs::read_dir(&self.directory)?, |dir| {
dir.into_iter()
.filter_map(|entry| self.logfile_index(entry.path()))
.max()
})?;
// If we've found any logs, let's make sure we stay under `self.max_index` files.
if let Some(mut max_found_index) = max_found_index {
// First, let's check if we have the maximum amount of logs available (or maybe even more!)
if max_found_index >= self.max_index {
// If so, let's remove all of the ones >=self.max_index so that we can make room for one more
(self.max_index..=max_found_index)
.try_for_each(|index| fs::remove_file(self.make_filepath(index)))?;
// We'll need to update our `max_found_index` to avoid trying to
// move stuff that isn't there, but we'll use a saturating
// subtraction to handle the case where self.max_index == 0
// (only one logfile ever)
max_found_index = self.max_index.saturating_sub(1);
}
// If we've got a non-zero max index, we've got files to shuffle around!
if self.max_index != 0 {
// Increment all the remaining log files' indices so that we have
// room for a new one with index 0. Make sure that we do this in reverse order so
// we don't trample anything!
(0..=max_found_index)
.rev()
.try_for_each(|index| self.increment_index(index))?;
}
}
// Make sure we pass `create_new` so that nobody tries to be sneaky and
// place a file under us
fs::OpenOptions::new()
.create_new(true)
.write(true)
.open(self.make_filepath(0))
}
fn current_file(&mut self) -> io::Result<&mut fs::File> {
if self.should_rotate() {
self.rotate()?;
}
Ok(self
.current_file
.as_mut()
.expect("should've been created before"))
}
/// Manually rotate the file out
///
/// This is the only way that a file whose `rotation_period` is [`RotationPeriod::Manual`] can rotate.
///
/// # Errors
///
/// Returns an error if one is encountered during creation of the new logfile.
///
/// [`RotationPeriod::Manual`]: enum.RotationPeriod.html#variant.Manual
pub fn rotate(&mut self) -> io::Result<()> {
self.current_file = Some(self.create_file()?);
self.rotation_tracker.reset();
Ok(())
}
}
impl Write for RotatingFile {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
let written = self.current_file()?.write(buf)?;
self.rotation_tracker.wrote(&buf[..written]);
Ok(written)
}
fn flush(&mut self) -> io::Result<()> {
self.current_file()?.flush()
}
}
#[cfg(test)]
mod tests {
use std::fs;
use std::num::NonZeroUsize;
use std::path::Path;
use proptest::prelude::*;
use super::{RotatingFile, RotationPeriod};
#[track_caller]
fn assert_contains_files<P: AsRef<Path>>(
directory: P,
num: usize,
) -> Result<(), TestCaseError> {
let p = directory.as_ref();
prop_assert_eq!(
fs::read_dir(p).unwrap().count(),
num,
"Directory {:?} did not contain {} file(s) (at {})",
p,
num,
std::panic::Location::caller()
);
Ok(())
}
proptest! {
#![proptest_config(ProptestConfig {
cases: 15,
..ProptestConfig::default()
})]
#[test]
fn test_max_files(name in "[a-zA-Z_-]+", n in 1..25usize) {
let directory = tempfile::tempdir().unwrap();
let mut file = RotatingFile::new(
name,
directory.path().to_owned(),
RotationPeriod::Manual,
NonZeroUsize::new(n).unwrap(),
crate::Compression::None
);
assert_contains_files(&directory, 0)?;
for i in 0..n {
file.rotate().unwrap();
assert_contains_files(&directory, i+1)?;
}
for _ in 0..n {
assert_contains_files(&directory, n)?;
file.rotate().unwrap();
}
}
#[test]
fn test_roundtrip_uncompressed(name in "[a-zA-Z_-]+", data: Vec<u8>) {
use std::io::prelude::*;
let directory = tempfile::tempdir().unwrap();
let mut file = RotatingFile::new(
name,
directory.path().to_owned(),
RotationPeriod::Manual,
NonZeroUsize::new(10).unwrap(),
crate::Compression::None
);
file.write_all(&data).unwrap();
file.rotate().unwrap();
file.write_all(&data).unwrap();
drop(file);
for entry in fs::read_dir(&directory).unwrap().map(Result::unwrap) {
let path = entry.path();
let read = fs::read(path).unwrap();
prop_assert_eq!(&read, &data);
}
}
#[test]
fn test_roundtrip_zstd(name in "[a-zA-Z_-]+", n in 1..25usize, level in 0..21, data: Vec<u8>) {
use std::io::prelude::*;
let directory = tempfile::tempdir().unwrap();
let mut file = RotatingFile::new(
name,
directory.path().to_owned(),
RotationPeriod::Manual,
NonZeroUsize::new(n * 10).unwrap(),
crate::Compression::Zstd { level }
);
file.write_all(&data).unwrap();
for i in 0..n {
assert_contains_files(&directory, i + 1)?;
file.rotate().unwrap();
file.write_all(&data).unwrap();
}
assert_contains_files(&directory, n + 1)?;
drop(file);
for entry in fs::read_dir(&directory).unwrap().map(Result::unwrap) {
let path = entry.path();
let read = fs::read(&path).unwrap();
if path.file_stem().unwrap().to_string_lossy().ends_with(".0") {
prop_assert_eq!(path.extension().unwrap().to_string_lossy(), "log");
prop_assert_eq!(&read, &data);
} else {
prop_assert_eq!(path.extension().unwrap().to_string_lossy(), "zstd");
let read = zstd::decode_all(std::io::Cursor::new(read)).unwrap();
prop_assert_eq!(&read, &data);
}
}
}
}
}